Tagged: Photosynthesis Toggle Comment Threads | Keyboard Shortcuts

  • richardmitnick 3:27 pm on June 24, 2021 Permalink | Reply
    Tags: "An artificial leaf made from semiconducting polymers", Photosynthesis,   

    From Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH): “An artificial leaf made from semiconducting polymers” 

    From Swiss Federal Institute of Technology in Lausanne [EPFL-École Polytechnique Fédérale de Lausanne] (CH)

    24.06.21
    Laboratoire LIMNO EPFL SB

    EPFL scientists are generating oxygen from sunlight, water and semiconducting polymers. They present a promising way towards economical and scalable solar fuel production.

    Natural photosynthesis evolved to covert water and sunlight into oxygen (O2) and stored chemical energy. In plants this process is not very efficient, however the possibility to convert sunlight into chemical fuel in an economical and globally scalable manner is a very attractive method for reducing our dependence on fossil fuels. As such, scientists have been searching for routes toward efficient and inexpensive mimics of natural photosynthesis for decades. It turns out that the O2 production step is quite tricky and remains a major challenge toward artificial photosynthesis.

    Now, in a recent report published in Nature Catalysis, Prof. Kevin Sivula and his co-workers in the Laboratory for Molecular Engineering of Optoelectronic Nanomaterials (LIMNO) at EPFL describe a mixture of semiconducting polymers, commonly known as plastic electronics, that demonstrates highly efficient solar-driven water oxidation (H2O → O2).

    1
    Generating oxygen from sunlight, water and semiconducting polymers © LIMNO / EPFL.

    Compared to previously-reported systems, which employ inorganic materials such as metal oxides or silicon and have not met the performance and cost requirements for industrialization, the polymeric materials reported in this new work have molecularly tunable properties, and are solution-processable at low temperature, allowing large scale device fabrication at low manufacturing cost.

    The EPFL team’s breakthrough was realized by tuning the properties of the polymers to match the requirements of the water oxidation reaction and by assembling them into what is called “a bulk heterojunction” (BHJ) blend that further improves the efficiency of the solar-driven catalytic reaction. By also optimizing the conduction of the electronic charges in the device by using carefully engineered interfaces, they realized the first demonstration of a water oxidizing “photo-anode” based on a BHJ polymer blend that exhibits a benchmark performance to date – performing two orders of magnitude better than previous organic-based devices. Moreover, the team identified key factors that influence the robust performance of O2 production, which will help define paths forward to further improve the performance.

    By virtue of the potential of this approach, the system developed by Prof. Kevin Sivula and colleagues could substantially contribute to advancing the field of polymer-based electronics and establishing a promising route towards economical, efficient, and scalable solar fuel production by artificial photosynthesis.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL bloc

    EPFL campus

    The Swiss Federal Institute of Technology in Lausanne [EPFL-École polytechnique fédérale de Lausanne] (CH) is a research institute and university in Lausanne, Switzerland, that specializes in natural sciences and engineering. It is one of the two Swiss Federal Institutes of Technology, and it has three main missions: education, research and technology transfer.

    The QS World University Rankings ranks EPFL(CH) 14th in the world across all fields in their 2020/2021 ranking, whereas Times Higher Education World University Rankings ranks EPFL(CH) as the world’s 19th best school for Engineering and Technology in 2020.

    EPFL(CH) is located in the French-speaking part of Switzerland; the sister institution in the German-speaking part of Switzerland is the Swiss Federal Institute of Technology ETH Zürich [Eidgenössische Technische Hochschule Zürich)](CH) . Associated with several specialized research institutes, the two universities form the Domain of the Swiss Federal Institutes of Technology (ETH Domain) [ETH-Bereich; Domaine des Écoles polytechniques fédérales] (CH) which is directly dependent on the Federal Department of Economic Affairs, Education and Research. In connection with research and teaching activities, EPFL(CH) operates a nuclear reactor CROCUS; a Tokamak Fusion reactor; a Blue Gene/Q Supercomputer; and P3 bio-hazard facilities.

    The roots of modern-day EPFL(CH) can be traced back to the foundation of a private school under the name École spéciale de Lausanne in 1853 at the initiative of Lois Rivier, a graduate of the École Centrale Paris (FR) and John Gay the then professor and rector of the Académie de Lausanne. At its inception it had only 11 students and the offices was located at Rue du Valentin in Lausanne. In 1869, it became the technical department of the public Académie de Lausanne. When the Académie was reorganised and acquired the status of a university in 1890, the technical faculty changed its name to École d’ingénieurs de l’Université de Lausanne. In 1946, it was renamed the École polytechnique de l’Université de Lausanne (EPUL). In 1969, the EPUL was separated from the rest of the University of Lausanne and became a federal institute under its current name. EPFL(CH), like ETH Zürich(CH), is thus directly controlled by the Swiss federal government. In contrast, all other universities in Switzerland are controlled by their respective cantonal governments. Following the nomination of Patrick Aebischer as president in 2000, EPFL(CH) has started to develop into the field of life sciences. It absorbed the Swiss Institute for Experimental Cancer Research (ISREC) in 2008.

    In 1946, there were 360 students. In 1969, EPFL(CH) had 1,400 students and 55 professors. In the past two decades the university has grown rapidly and as of 2012 roughly 14,000 people study or work on campus, about 9,300 of these being Bachelor, Master or PhD students. The environment at modern day EPFL(CH) is highly international with the school attracting students and researchers from all over the world. More than 125 countries are represented on the campus and the university has two official languages, French and English.

    Organization

    EPFL is organised into eight schools, themselves formed of institutes that group research units (laboratories or chairs) around common themes:

    School of Basic Sciences (SB, Jan S. Hesthaven)

    Institute of Mathematics (MATH, Victor Panaretos)
    Institute of Chemical Sciences and Engineering (ISIC, Emsley Lyndon)
    Institute of Physics (IPHYS, Harald Brune)
    European Centre of Atomic and Molecular Computations (CECAM, Ignacio Pagonabarraga Mora)
    Bernoulli Center (CIB, Nicolas Monod)
    Biomedical Imaging Research Center (CIBM, Rolf Gruetter)
    Interdisciplinary Center for Electron Microscopy (CIME, Cécile Hébert)
    Max Planck-EPFL Centre for Molecular Nanosciences and Technology (CMNT, Thomas Rizzo)
    Swiss Plasma Center (SPC, Ambrogio Fasoli)
    Laboratory of Astrophysics (LASTRO, Jean-Paul Kneib)

    School of Engineering (STI, Ali Sayed)

    Institute of Electrical Engineering (IEL, Giovanni De Micheli)
    Institute of Mechanical Engineering (IGM, Thomas Gmür)
    Institute of Materials (IMX, Michaud Véronique)
    Institute of Microengineering (IMT, Olivier Martin)
    Institute of Bioengineering (IBI, Matthias Lütolf)

    School of Architecture, Civil and Environmental Engineering (ENAC, Claudia R. Binder)

    Institute of Architecture (IA, Luca Ortelli)
    Civil Engineering Institute (IIC, Eugen Brühwiler)
    Institute of Urban and Regional Sciences (INTER, Philippe Thalmann)
    Environmental Engineering Institute (IIE, David Andrew Barry)

    School of Computer and Communication Sciences (IC, James Larus)

    Algorithms & Theoretical Computer Science
    Artificial Intelligence & Machine Learning
    Computational Biology
    Computer Architecture & Integrated Systems
    Data Management & Information Retrieval
    Graphics & Vision
    Human-Computer Interaction
    Information & Communication Theory
    Networking
    Programming Languages & Formal Methods
    Security & Cryptography
    Signal & Image Processing
    Systems

    School of Life Sciences (SV, Gisou van der Goot)

    Bachelor-Master Teaching Section in Life Sciences and Technologies (SSV)
    Brain Mind Institute (BMI, Carmen Sandi)
    Institute of Bioengineering (IBI, Melody Swartz)
    Swiss Institute for Experimental Cancer Research (ISREC, Douglas Hanahan)
    Global Health Institute (GHI, Bruno Lemaitre)
    Ten Technology Platforms & Core Facilities (PTECH)
    Center for Phenogenomics (CPG)
    NCCR Synaptic Bases of Mental Diseases (NCCR-SYNAPSY)

    College of Management of Technology (CDM)

    Swiss Finance Institute at EPFL (CDM-SFI, Damir Filipovic)
    Section of Management of Technology and Entrepreneurship (CDM-PMTE, Daniel Kuhn)
    Institute of Technology and Public Policy (CDM-ITPP, Matthias Finger)
    Institute of Management of Technology and Entrepreneurship (CDM-MTEI, Ralf Seifert)
    Section of Financial Engineering (CDM-IF, Julien Hugonnier)

    College of Humanities (CDH, Thomas David)

    Human and social sciences teaching program (CDH-SHS, Thomas David)

    EPFL Middle East (EME, Dr. Franco Vigliotti)[62]

    Section of Energy Management and Sustainability (MES, Prof. Maher Kayal)

    In addition to the eight schools there are seven closely related institutions

    Swiss Cancer Centre
    Center for Biomedical Imaging (CIBM)
    Centre for Advanced Modelling Science (CADMOS)
    École cantonale d’art de Lausanne (ECAL)
    Campus Biotech
    Wyss Center for Bio- and Neuro-engineering
    Swiss National Supercomputing Centre

     
  • richardmitnick 12:51 pm on March 8, 2021 Permalink | Reply
    Tags: , Ben-Gurion University of the Negev אוניברסיטת בן-גוריון;בנגב(IL), , , Current coherence and classicality, Effect of environment on photosynthetic transfer efficiency, Investigating quantum effects in biology, Photosynthesis,   

    From Ben-Gurion University of the Negev אוניברסיטת בן-גוריון;בנגב(IL) via phys.org: “Do photosynthetic complexes use quantum coherence to increase their efficiency?” 

    From Ben-Gurion University of the Negev אוניברסיטת בן-גוריון;בנגב(IL)

    via


    phys.org

    March 8, 2021
    Thamarasee Jeewandara

    1
    Mechanisms of efficiency-driven evolution and environment-assisted quantum transport. (A) Schematic description of the evolutionary progress of photosynthetic complexes toward their current geometry, with efficiency being the evolutionary driving force. As evolution progresses, the structure of the photosynthetic complex evolves toward its current structure [the Fenna-Matthews-Olson (FMO) complex in this example] while increasing efficiency. Whether this is indeed the evolutionary pathway of photosynthetic complexes, and if so, whether quantum coherence is part of the efficiency enhancement is a central question in the field of quantum biology. (B) Schematic depiction of the population uniformization mechanism shown for a uniform chain of six sites (blue lines depict the sites in the chain; yellow arrows show the excitation of first site and extraction from fifth site). The density of the sites is described by blue bars for the quantum regime, ENAQT regime, and classical regime, along with a schematic form for the current versus dephasing curves. Credit: Science Advances.

    In a new report now published on Science Advances, Elinor Zerah Harush and Yonatan Dubi in the departments of chemistry and nanoscale science and technology, at the אוניברסיטת בן-גוריון;בנגב](IL]) Ben-Gurion University of the Negev(IL) discussed a direct evaluation of the effects of quantum coherence on the efficiency of three natural photosynthetic complexes. The open quantum systems approach allowed the researchers to simultaneously identify the quantum-nature and efficiency under natural physiological conditions. These systems resided in a mixed quantum-classical regime, which they characterized using dephasing-assisted transport. The efficiency was minimal at best therefore the presence of quantum coherence did not play a substantial role in the process. The efficiency was also independent of any structural parameters, suggesting the role of evolution during structural design for other uses.

    Investigating quantum effects in biology

    During photosynthesis, energy can be transferred from an antenna to a reaction center to collect light and convert it to chemical energy for use by the organism. Exciton-bound electron hole pairs formed the energy carriers in the photosynthetic process to carry harvested solar energy from the antenna to the reaction center via a network of bacteriochlorophylls (photosynthetic pigments that occur in bacteria), also known as the exciton-transfer complex (ETC). Interests on the ETC have expanded in the past decade where researchers used ultrafast nonlinear spectroscopy signals to demonstrate long-lived oscillations. The discovery of coherent oscillations in ETCs presented the hypothesis that quantum coherence occurred within natural photosynthetic complexes to assist energy transfer. Harush et al. sought to understand if quantum coherence could exist in the biological process of photosynthetic energy transfer. If so, was it used by the natural system for enhanced functional efficiency? While experimental and theoretical work have addressed these questions, they remain largely unanswered. In this work, the team addressed the questions using tools developed from the theory of open quantum systems. The findings suggest the unlikelihood for photosynthetic complexes to use quantum coherence to increase their efficiency.

    2
    Effect of environment on photosynthetic transfer efficiency in FMO and PC645. Calculated exciton current as a function of dephasing for the FMO (A) and PC-645 (B) complexes. The shaded green area indicates the estimated range of physiological dephasing rates. Insets show a schematic description of the exciton complexes. Credit: Science Advances.

    The experiments

    The team considered three different photosynthetic ETCs (exciton-transfer complexes) during the experiments. These include the Fenna-Matthews-Olson (FMO) complex—which appears in green sulfur bacteria, the cryptophyte phycocyanin-645 (PC-645) protein—a part of the photosynthetic apparatus in cryptophyte algae, and light harvesting 2 (LH2) – a part of the purple photosynthetic bacterium Rhodopseudomonas acidophila. All three complexes showed coherent energy transfer oscillations in nonlinear two-dimensional spectroscopy measurements. The team plotted the exciton current as a function of the dephasing rate for the FMO complex and the PC-645 complex. The similarity between the plots indicted relative insensitivity of the current to the internal structure Hamiltonian. Using the bacterial populations Harush et al. tested the level of “quantumness” of the system. They recognized this using a connection between the exciton population and dephasing rate through the mechanism of environment-assisted quantum transport (ENAQT). The ENAQT effect was clearly visible in the results since the current showed a maximum in the dephasing rate. However, the current enhancement was minute at approximately 0.0015% increase to indicate the unlikely nature of the complex to impose a meaningful evolutionary driving force.

    3
    Exciton density arrangement in the formation of ENAQT. (A) Density configuration (i.e., exciton occupation at different sites) of the FMO complex for three different regimes: quantum limit (blue line, γdeph = 10−4 μs−1), biological condition (yellow line, γdeph = 106 μs−1), and classic limit (green line, γdeph = 1012 μs−1). The transition from the quantum regime toward the classical regime is accompanied by a shift in the density configuration, from a wave function–determined configuration to a uniform gradient between the source and the sink, with a uniform configuration in between. To more clearly see this, (B), (C) and (D) present the schematic structure of FMO, where each sphere represents a BChl site, and the color brightness reflects its density. Credit: Science Advances.

    Effect of environment on photosynthetic transfer efficiency

    The team next investigated the LH2 (light harvesting-2) complex to understand the connection between ENAQT (environment-assisted quantum transport) and the population. This was difficult due to the lack of spatial separation between the antenna and reaction center in the construct. The LH2 complex contained two rings of bacteriophyll pigments; B800 (yellow ring) and B850 (blue ring) named after their energy absorption resonance in nanometers and absorbing energy in the visible region of the spectrum. Each part of the complex could absorb light to excite an exciton, which transferred from one of the rings to the reaction center allowing many exciton transfer-paths to occur. However, a current versus dephasing curve for LH2 revealed the importance of coherence during transport. The team then plotted current as a function of dephasing rate of the LH2 system and noted a very small increase in current approximating 0.05 percent.

    4
    Effect of environment on photosynthetic transfer efficiency in LH2. Average LH2 exciton current as a function of dephasing rate (black line), calculated for ≈900 possible paths. Pink curves show the current of arbitrary chosen realizations (i.e., entry and exit sites) in LH2. Shaded green area marks the natural dephasing rate. Inset: Schematic description of LH2 transfer network. Credit: Science Advances.

    Current coherence and classicality.

    The results of the study established the absence of a substantial increase in the exciton current when comparing the fully quantum case with the physiologically realistic dephasing rates. They also took classical systems in to account, which were not defined by the lack of any coherence, although their coherences could be fully determined from the populations without additional information. Researchers had previously quantified the distinction between quantum and classical systems. In a classical system, the two currents will be the same, implying that quantum coherences do not carry additional information across the classical dynamics.

    The outcome of this study indicated how the structures of interest relative to FMO, PC-645 and LH2 did not evolve to enhance the efficiency of the complexes. In the future, Elinor Zerah Harush and Yonatan Dubi intend to assess the origin of the observed dephasing time to acknowledge if the values calculated in the study are unique. The team also intend to understand other potential evolutionary advantages of the photosynthetic transfer complexes, which will guide biophysicists to broadly understand the possible role of quantum effects in photosynthetic complexes.

    See the full article here.

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Ben-Gurion University of the Negev (IL) אוניברסיטת בן-גוריון בנגב(IL) is a public research university in Beersheba, Israel. Ben-Gurion University of the Negev has five campuses: the Marcus Family Campus, Beer Sheva; the David Bergmann Campus, Beer Sheva; the David Tuviyahu Campus, Beer Sheva; the Sede Boqer Campus, and Eilat Campus.

    Ben-Gurion University is a center for teaching and research with about 20,000 students. Some of its research institutes include the National Institute for Biotechnology in the Negev, the Ilse Katz Institute for Nanoscale Science and Technology, the Jacob Blaustein Institutes for Desert Research with the Albert Katz International School for Desert Studies, and the Ben-Gurion Research Institute for the Study of Israel and Zionism.

    Ben-Gurion University was established in 1969 as the University of the Negev with the aim of promoting the development of the Negev desert that comprises more than sixty percent of Israel. The University was later renamed after Israel’s founder and first prime minister, David Ben-Gurion, who believed that the future of the country lay in this region. After Ben-Gurion’s death in 1973, the University was renamed Ben-Gurion University of the Negev. The Presidents of the university have been Moshe Prywes (1973–75), Yosef Tekoah (1975–81), Shlomo Gazit (1982–85), Chaim Elata (1985–90), Avishay Braverman (1990–2006), Rivka Carmi (2006–18), and Daniel Chamovitz (2018–present).

    In 2016, long-time friends, the late Dr. Howard and Lottie Marcus bequeathed a legacy gift of $400 million to Ben-Gurion University. This is the largest bequest ever made to an Israeli university and the most generous donation to any institution in the State of Israel. The funds doubled the University’s existing endowment.

     
  • richardmitnick 10:20 pm on March 1, 2021 Permalink | Reply
    Tags: "How 'great' was the great oxygenation event?", , , , , Photosynthesis, Phylogenetic "trees" are widely used to unravel the history of species or human families but also of protein families., , The findings supported the scenario in which oxygen was already known to many life forms by the time the GOE took place., The phylogenetic trees the researchers obtained showed a burst of oxygen-based enzyme evolution about 3 billion years ago-something like half a billion years before the GOE., The research presents a completely new means of dating oxygen emergence and one that helps us understand how life as we know it now evolved., This burst dated to the time that bacteria left the oceans and began to colonize the land., Weizmann Institute of Science(IL)   

    From Weizmann Institute of Science(IL) via phys.org: “How ‘great’ was the great oxygenation event?” 

    Weizmann Institute of Science logo

    From Weizmann Institute of Science(IL)

    via


    From phys.org

    1
    Banded iron deposits like these contain clues to the Great Oxygenation Event. Credit: Weizmann Institute of Science.

    Around 2.5 billion years ago, our planet experienced what was possibly the greatest change in its history: According to the geological record, molecular oxygen suddenly went from nonexistent to becoming freely available everywhere. Evidence for the Great Oxygenation Event (GOE) is clearly visible, for example, in banded iron formations containing oxidized iron [above]. The GOE, of course, is what allowed oxygen-using organisms—respirators—and ultimately ourselves, to evolve. But was it indeed a ‘great event’ in the sense that the change was radical and sudden, or were the organisms alive at the time already using free oxygen, just at lower levels?

    Prof. Dan Tawfik of the Weizmann Institute of Science’s Biomolecular Sciences Department explains that the dating of the GOE is indisputable, as is the fact that the molecular oxygen was produced by photosynthetic microorganisms [cyanobacteria].

    An image of Cyanobacteria, Tolypothrix.

    Chemically speaking, energy taken from light split water into protons (hydrogen ions) and oxygen. The electrons produced in this process were used to form energy-storing compounds (sugars), and the oxygen, a by-product, was initially released into the surroundings.

    The question that has not been resolved, however, is: Did the production of oxygen coincide with the GOE, or did living organisms have access to oxygen even before that event? One side of this debate states that molecular oxygen would not have been available before the GOE, as the chemistry of the atmosphere and oceans prior to that time would have ensured that any oxygen released by photosynthesis would have immediately reacted chemically. A second side of the debate, however, suggests that some of the oxygen produced by the photosynthetic microorganisms may have remained free long enough for non-photosynthetic organisms to snap it up for their own use, even before the GOE. Several conjectures in between these two have proposed ‘oases,’ or short-lived ‘waves,’ of atmospheric oxygenation.

    Research student Jagoda Jabłońska in Tawfik’s group thought that the group’s focus—protein evolution—could help resolve the issue. That is, using methods of tracing how and when various proteins have evolved, she and Tawfik might find out when living organisms began to process oxygen. Such phylogenetic “trees” are widely used to unravel the history of species or human families but also of protein families, and Jabłońska decided to use a similar approach to unearth the evolution of oxygen-based enzymes.

    To begin the study, Jabłońska sorted through around 130 known families of enzymes that either make or use oxygen in bacteria and archaea—the sorts of life forms that would have been around in the Archean Eon (the period between the emergence of life, ca. 4 billion years ago, and the GOE). From these she selected around half, in which oxygen-using or -emitting activity was found in most or all of the family members and seemed to be the founding function. That is, the very first family member would have emerged as an oxygen enzyme. From these, she selected 36 whose evolutionary history could be traced conclusively. “Of course, it was far from simple,” says Tawfik. “Genes can be lost in some organisms, giving the impression they evolved later in members in which they held on. And microorganisms share genes horizontally, messing up the phylogenetic trees and leading to an overestimation of the enzyme’s age. We had to correct for the latter, especially.”

    The phylogenetic trees the researchers ultimately obtained showed a burst of oxygen-based enzyme evolution about 3 billion years ago—something like half a billion years before the GOE. Examining this time frame further, the scientists found that rather than coinciding with the takeover of atmospheric oxygen, this burst dated to the time that bacteria left the oceans and began to colonize the land. A few oxygen-using enzymes could be traced back even farther. If oxygen use had coincided with the GOE, the enzymes that use it would have evolved later, so the findings supported the scenario in which oxygen was already known to many life forms by the time the GOE took place.

    The scenario that Jabłońska and Tawfik propose looks something like this: Oxygen is one of the most chemically reactive elements around. Like one end of a battery, it readily accepts electrons, thus providing extra metabolic power. That makes it extremely useful to many life forms, but also potentially damaging. So photosynthetic organisms as well as other organisms living in their vicinity had to quickly develop ways to efficiently dispose of oxygen. This would account for the emergence of oxygen-utilizing enzymes that would remove molecular oxygen from cells. One microorganism’s waste, however, is another’s potential source of life. Oxygen’s unique reactivity enabled organisms to break down and use “resilient” molecules such as aromatics and lipids, so enzymes that take up and use oxygen likely began evolving soon after.

    Tawfik says, “This confirms the hypothesis that oxygen appeared and persisted in the biosphere well before the GOE. It took time to achieve the higher GOE level, but by then oxygen was widely known in the biosphere.”

    Jabłońska concludes, “Our research presents a completely new means of dating oxygen emergence and one that helps us understand how life as we know it now evolved.”

    Science paper:
    The evolution of oxygen-utilizing enzymes suggests early biosphere oxygenation
    Nature Ecology & Evolution

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Weizmann Institute Campus

    The Weizmann Institute of Science(IL) is one of the world’s leading multidisciplinary research institutions. Hundreds of scientists, laboratory technicians and research students working on its lushly landscaped campus embark daily on fascinating journeys into the unknown, seeking to improve our understanding of nature and our place within it.

    Guiding these scientists is the spirit of inquiry so characteristic of the human race. It is this spirit that propelled humans upward along the evolutionary ladder, helping them reach their utmost heights. It prompted humankind to pursue agriculture, learn to build lodgings, invent writing, harness electricity to power emerging technologies, observe distant galaxies, design drugs to combat various diseases, develop new materials and decipher the genetic code embedded in all the plants and animals on Earth.

    The quest to maintain this increasing momentum compels Weizmann Institute scientists to seek out places that have not yet been reached by the human mind. What awaits us in these places? No one has the answer to this question. But one thing is certain – the journey fired by curiosity will lead onward to a better future.

     
  • richardmitnick 12:38 pm on December 17, 2020 Permalink | Reply
    Tags: "A Well-Rooted Study", , , , Evapotranspiration from the trees cools down the forest., Photosynthesis, Tree water loss to the atmosphere tracked with satellite imagery., Trees really do link the ground to the sky by exchanging energy and matter between the soil and the atmosphere., , Using remote sensing to keep an eye on the trees offers an effective way to monitor groundwater along river corridors in the Southwest.   

    From UC Santa Barbara: “A Well-Rooted Study” 

    UC Santa Barbara Name bloc
    From UC Santa Barbara

    December 16, 2020

    Harrison Tasoff
    (805) 893-7220
    harrisontasoff@ucsb.edu

    Using remote sensing to keep an eye on the trees offers an effective way to monitor groundwater along river corridors in the Southwest.

    1
    Lush vegetation follows the path of the Virgin River as it cuts like a green ribbon across the desert of Washington County, Utah. Credit: Marc Mayes.

    Spend time in any of the world’s great forests and you’ll start seeing the trees as immense pillars holding the heavens aloft while firmly anchored in the earth. It’s as much fact as sentiment. Trees really do link the ground to the sky by exchanging energy and matter between the soil and the atmosphere. Researchers believe that understanding this connection could provide both a wealth of scientific insight into ecosystems and practical applications that address challenges such as water resource conservation and management.

    A recent study led by UC Santa Barbara’s Marc Mayes investigates how patterns in tree water loss to the atmosphere, tracked with satellite imagery, relates to groundwater supplies. The results validate at landscape-wide scales ideas that scientists have proposed based on decades of research in labs and greenhouses. What’s more, the techniques lend themselves to an accurate, efficient way of monitoring groundwater resources over large areas. The findings appear in the journal Hydrological Processes.

    For all their diversity, most plants have a very simple game plan. Using energy from sunlight, they combine water from the ground with carbon dioxide from the air to produce sugars and oxygen. During photosynthesis, plants open small pores in their leaves to take in CO2, which also allows water to escape. This process of water loss is called evapotranspiration — short for soil evaporation and plant transpiration — and it’s essentially a transaction cost of transporting the ingredients for photosynthesis to the leaves where the process occurs.

    Just like evaporating sweat cools down our own bodies, the evapotranspiration from the trees cools down the forest. With the proper understanding and technology, scientists can use thermal image data from satellites as well as manned and unmanned aircraft to understand the relationship between plants and groundwater: cooler temperatures correlate with more evapotranspiration.

    “The core hypothesis of this paper is that you can use relationships between plant water use [as] measured by [satellite] image data, and climate data including air temperature and rainfall, to gauge the availability of, and changes in, groundwater resources,” said Mayes, an Earth scientist and remote sensing expert based at the university’s Earth Research Institute (ERI).

    Mayes and his colleagues focused on the flora of dryland rivers — those in deserts and Mediterranean climates. Throughout these regions, many plants have evolved adaptations that minimize water loss, like slow growth, water retention or boom-bust lifecycles. However, plants that dominate river channels — species like sycamore, cottonwood and willows — evolved to take advantage of the surplus groundwater the habitat offers relative to the surrounding landscape.

    2
    Trees and shrubs flourish along the Santa Ynez River despite the area’s dry climate. Credit: MARC MAYES.

    “Rather than slowing down its water use when water becomes scarce, this vegetation will basically drink itself to death,” Mayes said. This makes it a good window into conditions below the surface.

    The team used satellite-based thermal imaging to look at temperatures across the San Pedro River corridor in southern Arizona. On cloud-free days the satellites can gather data on surface temperatures at high resolution over large areas of land. By comparing the temperatures along the river to those in nearby, more sparsely vegetated areas, the researchers were able to determine the extent of evapotranspiration along different parts of the river at different times. They found that it correlated with air temperature in water-rich environments and with rainfall in water-scarce environments.

    The findings support recent advances in our understanding of plant water use. The hotter and drier the air, the stronger it pulls water from the leaves, and the more water the plant uses. Consequently, Mayes and his colleagues expected to see evapotranspiration vary with air temperature as long as the stream has abundant groundwater for the plants to draw on.

    On the other hand, where groundwater is scarce, plants will close the openings on their leaves to avoid water loss; it’s more important to avoid drying out than to take advantage of the extra sunshine on a warm day. As a result, evapotranspiration will correlate much more strongly with rainfall and streamflow, which increases the supply of water to trees through their roots.

    Scientists had demonstrated the predictable effect of evapotranspiration in lowering surface temperatures in lab and small field experiments. However, this is the first study to demonstrate its impact over large areas. The technology that made this possible has matured only within the past five years.

    “This remote sensing method shows great promise for identifying the relevant climatic versus other controls on tree growth and health, even within narrow bands of vegetation along rivers,” said coauthor Michael Singer, a researcher at ERI and lead investigator on the project that funded Mayes’ work.

    In fact, these ecosystems are vitally important to the southwestern U.S. “Despite taking up about 2% of the landscape, over 90% of the biodiversity in the Southwest relies on these ecosystems,” said coauthor Pamela Nagler, a research scientist at the U.S. Geological Survey’s Southwest Biological Science Center.

    The same techniques used in the paper could be applied to the perennial challenge of groundwater monitoring. In fact, this idea helped motivate the study in the first place. “It’s very hard to monitor groundwater availability and change[s] in groundwater resources at the really local scales that matter,” Mayes said. “We’re talking about farmers’ fields or river corridors downstream of new housing developments.”

    Monitoring wells are effective, but provide information only for one point on the map. What’s more, they are expensive to drill and maintain. Flux towers can measure the exchange of gasses between the surface and the atmosphere, including water vapor. But they have similar drawbacks to wells in terms of cost and scale. Scientists and stakeholders want reliable, cost-effective methods to monitor aquifers that provide wide coverage at the same time as high resolution. It’s a tall order.

    While it may not be quite as precise as a well, remote thermal imaging from aircraft and satellites can check off all of these boxes. It offers wide coverage and high resolution using existing infrastructure. And although it works only along stream corridors, “an inordinate amount of agricultural land and human settlements in dry places ends up being where the water is, along stream paths,” Mayes said.

    3
    The researchers’ technique provides data on average vegetation water use, which paints a picture of groundwater resources below the San Pedro River. Credit: MARC MAYES.

    The idea is to look for shifts in the relationships of evapotranspiration to climate variables over time. These changes will signal a switch between water-rich and water-poor conditions. “Detecting that signal over large areas could be a valuable early warning sign of depleting groundwater resources,” Mayes said. The technique could inform monitoring and pragmatic decision-making on groundwater use.

    This study is part of a larger Department of Defense (DOD) project aimed at understanding how vulnerable riverine habitats are to droughts on DOD bases in dryland regions of the U.S. “We are using multiple methods to understand when and why these plants become stressed due to lack of water,” said Singer, the project’s lead scientist. “[We hope] this new knowledge can support the management of these sensitive ecological biomes, particularly on military bases in dryland regions, where these pristine habitats support numerous threatened and endangered species.”

    Mayes added, “What’s coming down the pipe is a whole ensemble of work looking at ecosystem responses to water scarcity and water stress across space and time that informs ways we both understand ecosystem response and also improve the monitoring.”

    Other significant contributors to the study include Kelly Caylor, director of UC Santa Barbara’s Environmental Research Institute (ERI); Dar Roberts, a professor of geography and an ERI scientist with expertise in terrestrial ecosystems; and John Stella, a professor at SUNY College of Environmental Science and Forestry. This study was conducted under the DOD’s Strategic Environmental Research and Development Program.

    See the full article here .

    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education CoalitionUC Santa Barbara Seal
    The University of California, Santa Barbara (commonly referred to as UC Santa Barbara or UCSB) is a public research university and one of the 10 general campuses of the University of California system. Founded in 1891 as an independent teachers’ college, UCSB joined the University of California system in 1944 and is the third-oldest general-education campus in the system. The university is a comprehensive doctoral university and is organized into five colleges offering 87 undergraduate degrees and 55 graduate degrees. In 2012, UCSB was ranked 41st among “National Universities” and 10th among public universities by U.S. News & World Report. UCSB houses twelve national research centers, including the renowned Kavli Institute for Theoretical Physics.

     
  • richardmitnick 11:32 pm on February 12, 2020 Permalink | Reply
    Tags: , , Biophysical chemistry, Chromophores, Macromolecular crystallography, , Photoisomerization, Photosynthesis, ,   

    From SLAC National Accelerator Lab: “Researchers show how electric fields affect a molecular twist within light-sensitive proteins” 

    From SLAC National Accelerator Lab

    February 12, 2020
    By Ali Sundermier

    A better understanding of this phenomenon, which is crucial to many processes that occur in biological systems and materials, could enable researchers to develop light-sensitive proteins for areas such as biological imaging and optogenetics.

    A team of scientists from the Department of Energy’s SLAC National Accelerator Laboratory and Stanford University has gained insight into how electric fields affect the way energy from light drives molecular motion and transformation in a protein commonly used in biological imaging. A better understanding of this phenomenon, which is crucial to many processes that occur in biological systems and materials, could enable researchers to finely tune a system’s properties to harness these effects, for instance using light to control neurons in the brain. Their findings were published in Science in January.

    Twist and shout

    Human vision, photosynthesis and other natural processes harvest light with proteins that contain molecules known as chromophores, many of which twist when light hits them. The hallmark of this twisting motion, called photoisomerization, is that part of the molecule rotates around a particular chemical bond.

    2
    When light hits certain chromophores in proteins, it causes them to twist and change shape. This atomic reconfiguration, known as photoisomerization, changes the molecule’s chemical and physical properties. The hallmark of this process is a rotation that occurs around a chemical bond in the molecule. New research shows that the electric fields within a protein play a large role in determining which bond this rotation occurs around. (Chi-Yun Lin/Stanford University)

    “Something about the protein environment is steering this very specific and important process,” says Steven Boxer, a biophysical chemist and Stanford professor who oversaw the research. “One possibility is that the distribution of atoms in the molecular space blocks or allows rotation about each chemical bond, known as the steric effect. An alternative has to do with the idea that when molecules with double bonds are excited, there is a separation of charge, and so the surrounding electric fields might favor the rotation of one bond over another. This is called the electrostatic effect.”

    A different tune

    To find out more about this process, the researchers looked at green fluorescent protein, a protein frequently used in biological imaging whose chromophore can respond to light in a number of ways that are sensitive to its local environment within the protein, producing fluorescent light of various colors and intensities.

    Stanford graduate students Matt Romei and Chi-Yun Lin, who led the study, tuned the electronic properties of the chromophore within the protein by introducing chemical groups that systematically added or subtracted electrons from the chromophore to engineer an electric field effect. Then they measured how this affected the chromophore’s twisting motion.

    With the help of coauthor Irimpan Mathews, a scientist at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), the researchers used an X-ray technique called macromolecular crystallography at SSRL beamlines 7-1, 12-2 and 14-1 to map the structures of these tuned proteins to show that these changes had little effect on the atomic structure of the chromophore and surrounding protein.

    SLAC/SSRL

    Then, using a combination of techniques, they were able to measure how changes to the chromophore’s electron distribution affected where rotation occurred when it was hit by light.

    “Until now, most of the research on photoisomerization in this particular protein has been either theoretical or focused on the steric effect,” Romei says. “This research is one of the first to investigate the phenomenon experimentally and show the importance of the electrostatic effect. Once we plotted the data, we saw these really nice trends that suggest that tuning the chromophore’s electronic properties has a huge impact on its bond isomerization properties.”

    Honing tools

    These results also suggest ways to design light-sensitive proteins by manipulating the environment around the chromophore. Lin adds that this same experimental approach could be used to study and control the electrostatic effect in many other systems.

    “We’re trying to figure out the principle that controls this process,” Lin says. “Using what we learn, we hope to apply these concepts to develop better tools in fields such as optogenetics, where you can selectively manipulate nerves to lead to certain functions in the brain.”

    Boxer adds that the idea that the organized electric fields within proteins are important for many biological functions is an emerging concept that could be of interest to a broad audience.

    “Much of the work in our lab focuses on developing methods to measure these fields and connect them with function such as enzymatic catalysis,” he says, “and we now see that photoisomerization fits into this framework.”

    This work was funded in part by the National Institutes of Health (NIH). SSRL is a DOE Office of Science user facility. The SSRL Structural Molecular Biology Program is supported by the NIH and the DOE Office of Biological and Environmental Research. Part of this work was performed at the Stanford Nano Shared Facilities and supported by the National Science Foundation.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC/LCLS


    SLAC/LCLS II projected view


    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

    SSRL and LCLS are DOE Office of Science user facilities.

     
  • richardmitnick 8:32 am on May 8, 2019 Permalink | Reply
    Tags: "North Atlantic Ocean productivity has dropped 10 percent during Industrial era", , DMS-dimethylsulfide, , , MSA-methanesulfonic acid, Photosynthesis, , The decline coincides with steadily rising surface temperatures over the same period of time.   

    From MIT News: “North Atlantic Ocean productivity has dropped 10 percent during Industrial era” 

    MIT News
    MIT Widget

    From MIT News

    May 6, 2019
    Jennifer Chu

    Phytoplankton decline coincides with warming temperatures over the last 150 years.

    1
    Matt Osman, a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences, overlooking a frozen Baffin Bay to the west, Nuussuaq Peninsula Ice Cap, west Greenland. Image: Luke Trusel (Rowan University).

    2
    Ice core field camp on a clear spring evening, Disko Island Ice Cap, west Greenland. Image: Luke Trusel (Rowan University).

    3
    Iceberg in Disko Bay, west Greenland. Image: Luke Trusel (Rowan University)

    4
    Retrieving an ice core section from the drill barrel during a west Greenland snowstorm, west Greenland Ice Sheet. Image: Sarah Das (WHOI).

    Virtually all marine life depends on the productivity of phytoplankton — microscopic organisms that work tirelessly at the ocean’s surface to absorb the carbon dioxide that gets dissolved into the upper ocean from the atmosphere.

    Through photosynthesis, these microbes break down carbon dioxide into oxygen, some of which ultimately gets released back to the atmosphere, and organic carbon, which they store until they themselves are consumed. This plankton-derived carbon fuels the rest of the marine food web, from the tiniest shrimp to giant sea turtles and humpback whales.

    Now, scientists at MIT, Woods Hole Oceanographic Institution (WHOI), and elsewhere have found evidence that phytoplankton’s productivity is declining steadily in the North Atlantic, one of the world’s most productive marine basins.

    In a paper appearing today in Nature, the researchers report that phytoplankton’s productivity in this important region has gone down around 10 percent since the mid-19th century and the start of the Industrial era. This decline coincides with steadily rising surface temperatures over the same period of time.

    Matthew Osman, the paper’s lead author and a graduate student in MIT’s Department of Earth, Atmospheric, and Planetary Sciences and the MIT/WHOI Joint Program in Oceanography, says there are indications that phytoplankton’s productivity may decline further as temperatures continue to rise as a result of human-induced climate change.

    “It’s a significant enough decine that we should be concerned,” Osman says. “The amount of productivity in the oceans roughly scales with how much phytoplankton you have. So this translates to 10 percent of the marine food base in this region that’s been lost over the industrial era. If we have a growing population but a decreasing food base, at some point we’re likely going to feel the effects of that decline.”

    Drilling through “pancakes” of ice

    Osman and his colleagues looked for trends in phytoplankton’s productivity using the molecular compound methanesulfonic acid, or MSA. When phytoplankton expand into large blooms, certain microbes emit dimethylsulfide, or DMS, an aerosol that is lofted into the atmosphere and eventually breaks down as either sulfate aerosol, or MSA, which is then deposited on sea or land surfaces by winds.

    “Unlike sulfate, which can have many sources in the atmosphere, it was recognized about 30 years ago that MSA had a very unique aspect to it, which is that it’s only derived from DMS, which in turn is only derived from these phytoplankton blooms,” Osman says. “So any MSA you measure, you can be confident has only one unique source — phytoplankton.”

    In the North Atlantic, phytoplankton likely produced MSA that was deposited to the north, including across Greenland. The researchers measured MSA in Greenland ice cores — in this case using 100- to 200-meter-long columns of snow and ice that represent layers of past snowfall events preserved over hundreds of years.

    “They’re basically sedimentary layers of ice that have been stacked on top of each other over centuries, like pancakes,” Osman says.

    The team analyzed 12 ice cores in all, each collected from a different location on the Greenland ice sheet by various groups from the 1980s to the present. Osman and his advisor Sarah Das, an associate scientist at WHOI and co-author on the paper, collected one of the cores during an expedition in April 2015.

    “The conditions can be really harsh,” Osman says. “It’s minus 30 degrees Celsius, windy, and there are often whiteout conditions in a snowstorm, where it’s difficult to differentiate the sky from the ice sheet itself.”

    The team was nevertheless able to extract, meter by meter, a 100-meter-long core, using a giant drill that was delivered to the team’s location via a small ski-equipped airplane. They immediately archived each ice core segment in a heavily insulated cold storage box, then flew the boxes on “cold deck flights” — aircraft with ambient conditions of around minus 20 degrees Celsius. Once the planes touched down, freezer trucks transported the ice cores to the scientists’ ice core laboratories.

    “The whole process of how one safely transports a 100-meter section of ice from Greenland, kept at minus-20-degree conditions, back to the United States is a massive undertaking,” Osman says.

    Cascading effects

    The team incorporated the expertise of researchers at various labs around the world in analyzing each of the 12 ice cores for MSA. Across all 12 records, they observed a conspicuous decline in MSA concentrations, beginning in the mid-19th century, around the start of the Industrial era when the widescale production of greenhouse gases began. This decline in MSA is directly related to a decline in phytoplankton productivity in the North Atlantic.

    “This is the first time we’ve collectively used these ice core MSA records from all across Greenland, and they show this coherent signal. We see a long-term decline that originates around the same time as when we started perturbing the climate system with industrial-scale greenhouse-gas emissions,” Osman says. “The North Atlantic is such a productive area, and there’s a huge multinational fisheries economy related to this productivity. Any changes at the base of this food chain will have cascading effects that we’ll ultimately feel at our dinner tables.”

    The multicentury decline in phytoplankton productivity appears to coincide not only with concurrent long-term warming temperatures; it also shows synchronous variations on decadal time-scales with the large-scale ocean circulation pattern known as the Atlantic Meridional Overturning Circulation, or AMOC. This circulation pattern typically acts to mix layers of the deep ocean with the surface, allowing the exchange of much-needed nutrients on which phytoplankton feed.

    In recent years, scientists have found evidence that AMOC is weakening, a process that is still not well-understood but may be due in part to warming temperatures increasing the melting of Greenland’s ice. This ice melt has added an influx of less-dense freshwater to the North Atlantic, which acts to stratify, or separate its layers, much like oil and water, preventing nutrients in the deep from upwelling to the surface. This warming-induced weakening of the ocean circulation could be what is driving phytoplankton’s decline. As the atmosphere warms the upper ocean in general, this could also further the ocean’s stratification, worsening phytoplankton’s productivity.

    “It’s a one-two punch,” Osman says. “It’s not good news, but the upshot to this is that we can no longer claim ignorance. We have evidence that this is happening, and that’s the first step you inherently have to take toward fixing the problem, however we do that.”

    This research was supported in part by the National Science Foundation (NSF), the National Aeronautics and Space Administration (NASA), as well as graduate fellowship support from the US Department of Defense Office of Naval Research.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.


    Stem Education Coalition

    MIT Seal

    The mission of MIT is to advance knowledge and educate students in science, technology, and other areas of scholarship that will best serve the nation and the world in the twenty-first century. We seek to develop in each member of the MIT community the ability and passion to work wisely, creatively, and effectively for the betterment of humankind.

    MIT Campus

     
  • richardmitnick 3:03 pm on April 11, 2019 Permalink | Reply
    Tags: , Helical Carotenoid Protein, , , Photoprotection, Photosynthesis   

    From Michigan State University: “MSU researchers discover light absorbing protein in cyanobacteria” 

    Michigan State Bloc

    From Michigan State University

    April 11, 2019

    Igor Houwat
    MSU-DOE Plant Research Laboratory office
    (517) 353-2223
    houwatig@msu.edu

    1

    Cyanobacteria are tiny, hardy organisms. Each cell is 25 times smaller than a human hair. Their collective ability to do photosynthesis is why we have air to breathe and a diverse and complex biosphere.

    Scientists are interested in what makes cyanobacteria great at photosynthesis. Some want to isolate and copy successful processes which would then be repurposed for human usage, like in medicine or for renewable energy.

    One of these processes is photoprotection. It includes a network of proteins that detect surrounding light levels and protect cyanobacteria from damages caused by overexposure to bright light.

    The lab of Cheryl Kerfeld at Michigan State University recently discovered a family of proteins, the Helical Carotenoid Protein, or HCP, that are the evolutionary ancestors of today’s photoprotective proteins. Although ancient, HCP still live on alongside their modern descendants.

    This discovery has opened new avenues to explore photoprotection and for the first time, the Kerfeld lab structurally and biophysically characterizes one of these proteins. They call it HCP2. The study is in the journal BBA-Bioenergetics.

    Structurally, the HCP2 is a monomer when isolated in a solution, but in its crystallized form, it curiously shows up as a dimer.

    “We don’t think that the dimer is the protein’s form when it is in the cyanobacteria,” says Maria Agustina Dominguez-Martin, a post-doc in the Kerfeld lab. “Most likely, HCP2 binds to a yet unknown partner. The dimer situation during crystallization is artificial, because the only available molecules in the environment are others like itself.”

    The scientists try to determine HCP2s functions. It is a good quencher of reactive oxygen species, damaging byproducts of photosynthesis. But since many other proteins can do that as well, Dominguez-Martin doesn’t think that is HCP2’s main function.

    “We have yet to identify a primary function,” Dominguez-Martin says. “The difficulty is that the HCP family is a recent discovery, so we don’t have much basis for comparison.”

    The ability to detect light is key for applications, especially in biotech. One promising area is optogenetics, a technology that uses light to control living cells. Optogenetics systems are like light switches that activate predetermined functions when struck by a light source.

    HCP2 could play a part in such applications. But this is all far down the road.

    “There are 9 evolutionary families of HCP to explore,” Dominguez-Martin said. “That adds up to hundreds of variants with possibly distinctive functions that we have yet to discover. With that in mind, we’re characterizing other proteins from the HCP family to expand our available data set.”

    Because these proteins likely play a role in photoprotection, they may represent a system that scientists could engineer for “smart photoprotection,” reducing wasteful photoprotection which would then help photosynthetic organisms become more efficient.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    Michigan State Campus

    Michigan State University (MSU) is a public research university located in East Lansing, Michigan, United States. MSU was founded in 1855 and became the nation’s first land-grant institution under the Morrill Act of 1862, serving as a model for future land-grant universities.

    MSU pioneered the studies of packaging, hospitality business, plant biology, supply chain management, and telecommunication. U.S. News & World Report ranks several MSU graduate programs in the nation’s top 10, including industrial and organizational psychology, osteopathic medicine, and veterinary medicine, and identifies its graduate programs in elementary education, secondary education, and nuclear physics as the best in the country. MSU has been labeled one of the “Public Ivies,” a publicly funded university considered as providing a quality of education comparable to those of the Ivy League.

    Following the introduction of the Morrill Act, the college became coeducational and expanded its curriculum beyond agriculture. Today, MSU is the seventh-largest university in the United States (in terms of enrollment), with over 49,000 students and 2,950 faculty members. There are approximately 532,000 living MSU alumni worldwide.

     
  • richardmitnick 1:50 pm on November 7, 2018 Permalink | Reply
    Tags: , , , , , Photosynthesis, , Researchers create most complete high-res atomic movie of photosynthesis to date, , ,   

    From SLAC National Accelerator Lab: “Researchers create most complete high-res atomic movie of photosynthesis to date” 

    From SLAC National Accelerator Lab

    November 7, 2018

    Andrew Gordon
    agordon@slac.stanford.edu
    (650) 926-2282

    In a major step forward, SLAC’s X-ray laser captures all four stable states of the process that produces the oxygen we breathe, as well as fleeting steps in between. The work opens doors to understanding the past and creating a greener future.

    1
    Using SLAC’s X-ray laser, researchers have captured the most complete high-res atomic movie to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. (Gregory Stewart, SLAC National Accelerator Laboratory)

    Despite its role in shaping life as we know it, many aspects of photosynthesis remain a mystery. An international collaboration between scientists at SLAC National Accelerator Laboratory, Lawrence Berkeley National Laboratory and several other institutions is working to change that. The researchers used SLAC’s Linac Coherent Light Source (LCLS) X-ray laser to capture the most complete and highest-resolution picture to date of Photosystem II, a key protein complex in plants, algae and cyanobacteria responsible for splitting water and producing the oxygen we breathe. The results were published in Nature today.

    SLAC/LCLS

    Explosion of life

    When Earth formed about 4.5 billion years ago, the planet’s landscape was almost nothing like what it is today. Junko Yano, one of the authors of the study and a senior scientist at Berkeley Lab, describes it as “hellish.” Meteors sizzled through a carbon dioxide-rich atmosphere and volcanoes flooded the surface with magmatic seas.

    Over the next 2.5 billion years, water vapor accumulating in the air started to rain down and form oceans where the very first life appeared in the form of single-celled organisms. But it wasn’t until one of those specks of life mutated and developed the ability to harness light from the sun and turn it into energy, releasing oxygen molecules from water in the process, that Earth started to evolve into the planet it is today. This process, oxygenic photosynthesis, is considered one of nature’s crown jewels and has remained relatively unchanged in the more than 2 billion years since it emerged.

    “This one reaction made us as we are, as the world. Molecule by molecule, the planet was slowly enriched until, about 540 million years ago, it exploded with life,” said co-author Uwe Bergmann, a distinguished staff scientist at SLAC. “When it comes to questions about where we come from, this is one of the biggest.”

    A greener future

    Photosystem II is the workhorse responsible for using sunlight to break water down into its atomic components, unlocking hydrogen and oxygen. Until recently, it had only been possible to measure pieces of this process at extremely low temperatures. In a previous paper, the researchers used a new method to observe two steps of this water-splitting cycle [Nature]at the temperature at which it occurs in nature.

    Now the team has imaged all four intermediate states of the process at natural temperature and the finest level of detail yet. They also captured, for the first time, transitional moments between two of the states, giving them a sequence of six images of the process.

    The goal of the project, said co-author Jan Kern, a scientist at Berkeley Lab, is to piece together an atomic movie using many frames from the entire process, including the elusive transient state at the end that bonds oxygen atoms from two water molecules to produce oxygen molecules.

    “Studying this system gives us an opportunity to see how metals and proteins work together and how light controls such kinds of reactions,” said Vittal Yachandra, one of the authors of the study and a senior scientist at Berkeley Lab who has been working on Photosystem II for more than 35 years. “In addition to opening a window on the past, a better understanding of Photosystem II could unlock the door to a greener future, providing us with inspiration for artificial photosynthetic systems that produce clean and renewable energy from sunlight and water.”

    Sample assembly line

    For their experiments, the researchers grow what Kern described as a “thick green slush” of cyanobacteria — the very same ancient organisms that first developed the ability to photosynthesize — in a large vat that is constantly illuminated. They then harvest the cells for their samples.

    At LCLS, the samples are zapped with ultrafast pulses of X-rays [Science] to collect both X-ray crystallography and spectroscopy data to map how electrons flow in the oxygen-evolving complex of photosystem II. In crystallography, researchers use the way a crystal sample scatters X-rays to map its structure; in spectroscopy, they excite the atoms in a material to uncover information about its chemistry. This approach, combined with a new assembly-line sample transportation system [Nature Methods], allowed the researchers to narrow down the proposed mechanisms put forward by the research community over the years.

    Mapping the process

    Previously, the researchers were able to determine the room-temperature structure of two of the states at a resolution of 2.25 angstroms; one angstrom is about the diameter of a hydrogen atom. This allowed them to see the position of the heavy metal atoms, but left some questions about the exact positions of the lighter atoms, like oxygen. In this paper, they were able to improve the resolution even further, to 2 angstroms, which enabled them to start seeing the position of lighter atoms more clearly, as well as draw a more detailed map of the chemical structure of the metal catalytic center in the complex where water is split.

    This center, called the oxygen-evolving complex, is a cluster of four manganese atoms and one calcium atom bridged with oxygen atoms. It cycles through the four stable oxidation states, S0-S3, when exposed to sunlight. On a baseball field, S0 would be the start of the game when a player on home base is ready to go to bat. S1-S3 would be players on first, second, and third. Every time a batter connects with a ball, or the complex absorbs a photon of sunlight, the player on the field advances one base. When the fourth ball is hit, the player slides into home, scoring a run or, in the case of Photosystem II, releasing breathable oxygen.

    The researchers were able to snap action shots of how the structure of the complex transformed at every base, which would not have been possible without their technique. A second set of data allowed them to map the exact position of the system in each image, confirming that they had in fact imaged the states they were aiming for.

    1
    In photosystem II, the water-splitting center cycles through four stable states, S0-S3. On a baseball field, S0 would be the start of the game when a batter on home base is ready to hit. S1-S3 would be players waiting on first, second, and third. The center gets bumped up to the next state every time it absorbs a photon of sunlight, just like how a player on the field advances one base every time a batter connects with a ball. When the fourth ball is hit, the player slides into home, scoring a run or, in the case of Photosystem II, releasing the oxygen we breathe. (Gregory Stewart/SLAC National Accelerator Laboratory)

    Sliding into home

    But there are many other things going on throughout this process, as well as moments between states when the player is making a break for the next base, that are a bit harder to catch. One of the most significant aspects of this paper, Yano said, is that they were able to image two moments in between S2 and S3. In upcoming experiments, the researchers hope to use the same technique to image more of these in-between states, including the mad dash for home — the transient state, or S4, where two atoms of oxygen bond together — providing information about the chemistry of the reaction that is vital to mimicking this process in artificial systems.

    “The entire cycle takes nearly two milliseconds to complete,” Kern said. “Our dream is to capture 50-microsecond steps throughout the full cycle, each of them with the highest resolution possible, to create this atomic movie of the entire process.”

    Although they still have a way to go, the researchers said that these results provide a path forward, both in unveiling the mysteries of how photosynthesis works and in offering a blueprint for artificial sources of renewable energy.

    “It’s been a learning process,” said SLAC scientist and co-author Roberto Alonso-Mori. “Over the last seven years we’ve worked with our collaborators to reinvent key aspects of our techniques. We’ve been slowly chipping away at this question and these results are a big step forward.”

    In addition to SLAC and Berkeley Lab, the collaboration includes researchers from Umeå University, Uppsala University, Humboldt University of Berlin, the University of California, Berkeley, the University of California, San Francisco and the Diamond Light Source.

    Key components of this work were carried out at SLAC’s Stanford Synchrotron Radiation Lightsource (SSRL), Berkeley Lab’s Advanced Light Source (ALS) and Argonne National Laboratory’s Advanced Photon Source (APS). LCLS, SSRL, APS, and ALS are DOE Office of Science user facilities. This work was supported by the DOE Office of Science and the National Institutes of Health, among other funding agencies.

    SLAC/SSRL

    LBNL/ALS

    ANL APS

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings
    Please help promote STEM in your local schools.

    Stem Education Coalition

    SLAC Campus
    SLAC is a multi-program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. Located in Menlo Park, California, SLAC is operated by Stanford University for the DOE’s Office of Science.

     
  • richardmitnick 11:44 am on September 28, 2018 Permalink | Reply
    Tags: Astrobiology Grand Tour, , , , Community of microbial mats living on top. They are some of the Earth’s earliest ecosystems., , First oxygen-producing bacteria-cyanobacteria, , Karijini National Park, Living stromatolites of Shark Bay, , , Photosynthesis, , Pilbara in Western Australia, Pilbara is also where the oldest mineral on Earth –a zircon dated at 4.4 billion years old — was discovered four years ago in the Jack Hills region, State of Western Australia, Stromatolites literally mean “layered rocks”, The most important contribution of stromatolites – terraforming the Earth, These ancient life forms left behind geological footprints reminding us they were here first, Time-Traveling in the Australian Outback in Search of Early Earth   

    From Many Worlds: “Time-Traveling in the Australian Outback in Search of Early Earth” 

    NASA NExSS bloc

    NASA NExSS

    Many Words icon

    From Many Worlds

    2018-09-28
    Nicholas Siegler, Chief Technologist for NASA’s Exoplanet Exploration Program at the Jet Propulsion Laboratory with the help of doctoral student Markus Gogouvitis, at the University of New South Wales, Australia and Georg-August-University in Gottingen, Germany.

    1
    These living stromatolites at Shark Bay, Australia are descendants of similar microbial/sedimentary forms once common around the world. They are among the oldest known repositories of life. Most stromatolites died off long ago, but remain at Shark Bay because of the high salinity of the water. (Tourism, Western Australia)

    This past July I joined a group of geologists, geochemists, microbiologists, and fellow astronomers on a tour of some of the best-preserved evidence for early life.

    Entitled the Astrobiology Grand Tour, it was a trip led by Dr. Martin Van Kranendonk, a structural geologist from the University of New South Wales, who had spent more than 25 years surveying Australia’s Pilbara region. Along with his graduate students he had organized a ten-day excursion deep into the outback of Western Australia to visit some of astrobiology’s most renowned sites.

    The trip would entail long, hot days of hiking through unmaintained trails on loose surface rocks covered by barb-like bushes called spinifex. As I was to find out, nature was not going to give up its secrets easily. And there were no special privileges allocated to astrophysicists from New Jersey [? no mention of anyone from New Jersey].

    2
    The route of our journey back in time. (Google Earth/Markus Gogouvitis /Martin Van Kranendonk)

    The state of Western Australia, almost four times the size of the American state of Texas but with less than a tenth of the population (2.6 million), is the site of many of astrobiology’s most heralded sites. For more than three billion years, it has been one of the most stable geologic regions in the world.

    It has been ideal for geological preservation due to its arid conditions, lack of tectonic movement, and remoteness. The rock records have in many places survived and are now able to tell their stories (to those who know how to listen).

    3
    The classic red rocks of the Pilbara in Western Australia, with the needle sharp spinifex bushes in the foreground. (Nick Siegler, NASA/JPL-Caltech)

    Our trip began with what felt like a pilgrimage. We left Western Australia’s largest city Perth and headed north for Shark bay. It felt a bit like a pilgrimage because the next morning we visited one of modern astrobiology’s highlights – the living stromatolites of Shark Bay.

    Stromatolites literally mean “layered rocks”. It’s not the rocks that are alive but rather the community of microbial mats living on top. They are some of the Earth’s earliest ecosystems.

    We gazed over these living microbial communities aloft on their rock perches and marveled at their exceptional longevity — the species has persisted for over three billion years. Their ancestors had survived global mass extinctions, planet-covering ice glaciers, volcanic activity, and all sorts of predators. Once these life forms took hold they were not going to let go.

    4
    The stromatolites forming today in the shallow waters of Shark Bay, Australia are built by colonies of microbes that capture ocean sediments. (University of Wisconsin-Madison)

    The photosynthetic bacteria that built ancient stromatolites played a central role of our trip for three reasons:

    Their geological footprints allowed scientists to date the evolution of early life and at times gain insight into the environments in which they grew.
    They eventually harbored the first oxygen-producing bacteria and played a central role in creating our oxygen-rich atmosphere.
    By locating ever-increasingly older microbial fossils we observed a lower limit to the age of the first life forms.. Given photosynthesis is not a simple process, the first life forms must have been simpler. Speculating, perhaps a few hundred million years earlier so that the first life form on Earth may have originated at four billion years ago.

    When viewed under a microscope, you can see the mats are made of millions of single cell bacteria and archaea, among the simplest life forms we know. Within these relatively thin regions are multiple layers of specialized microbial communities that live interdependently.

    Bacteria in the top layer evolved to harvest sunlight to live and grow via photosynthesis. Their waste products include oxygen as well as important nutrients for many different bacterial species within underlying layers. And this underlying layer’s waste product would do the same for the layer beneath it, perfectly recycling each other’s waste. The oldest forms of life that we know of had learned to co-exist together in a chemically interdependent environment.

    5
    Broken piece of a living stromatolite, which was was remarkably spongy and smelled slightly salty, indicative of the hypersaline bay that has contributed to their survival by making bacteria and other organisms undesirable. What was actually most remarkable of the visit to Hamelin pool was how quiet it was. There were no seagulls and other birds because of the hypersaline environment. They had gone elsewhere for their meals. (Nick Siegler, NASA/JPL-Caltech)

    We saw ripped up portions of the mats that washed upon the shore at Hamelin pool in Shark Bay. A whole ecosystem held in one’s hand. Thousands of millions of years ago ancient relatives of these microbes thrived in shallow waters all around our planet, and left behind fossilized remains. But due to the evolution of grazing organisms these microbial structures are nowadays constrained to very specific environments. In the case of Shark Bay, the very high salt contents of this inlet have warded off most predators providing the microbes with a safe haven to live.

    Ironically, the rocks, which help identify these ancient life forms, at the time were just a nuisance for the living microbes.

    Small fine grains of sedimentary rock carried along in the daily tides would occasionally get stuck in the sticky mucus the microbes would secrete. In addition, the photosynthetic bacteria found at Shark Bay may have been inadvertently making their own rock by depleting the carbon dioxide in the surrounding water as part of photosynthesis and precipitating carbonate, adding to the grains of sediment trapped within the sticky top layer.

    Over time, the grains from both the sedimentary and precipitated rocks would cover the surface and block the sunlight for which these organisms had evolved to depend on. As an evolutionary tour de force, the photosynthetic microbes learned to migrate upward, leaving the newly formed rock layers behind.

    These secondary rock fossils today showcase visually observable crinkly, frequently conical shapes, in stark contrast to abiotic sedimentary rocks. These ancient life forms left behind geological footprints reminding us they were here first.

    Now to the most important contribution of stromatolites – terraforming the Earth.

    Living in shallow water, the top most layer of the Shark Bay microbial mats are known to host cyanobacteria, photosynthetic bacteria that produce oxygen as a byproduct. Scientists don’t know what the first bacteria produced as they harnessed the energy of the Sun. But they do know that they eventually started producing oxygen.

    In the evolution of life that eventually led to all plants and animals, this was one of the great events. More than 2.5 billion years ago, ancient bacteria began diligently producing oxygen in the oceans. Earth’s atmosphere began to irreversibly shift from its original, oxygen-free existence, to an oxic one, initiating the formation of our ozone layer and paving the way for the evolution of more complex life. Our planet has been terraformed by micro-organisms!

    It was in the Karijini National Park where we went back in time (2.4 billion years) and observed an extraordinary piece of evidence for the early production of oxygen in Earth’s oceans, a time before oxygen made a strong presence in our atmosphere.

    6
    Banded iron formation at Karajini National Park. (Nick Siegler, NASA-JPL/Caltech)

    We saw a massive gorge with steep vertical walls carved out by flowing water. As oxygen production by early bacteria increased below the water surface it would react with dissolved iron ions (early oceans were iron-rich) causing iron oxides to precipitate and settle to the bottom.

    For reasons not entirely understood — perhaps related to seasonal or temperature effects– the amount of new oxygen temporarily decreased and iron ion remained soluble in the oceans and other types of sediments accumulated, carbonates, slate, and shale. And then, just as before, the oxygen reappeared creating a new layer of precipitated iron.

    The result was a banded sedimentary rock, a litmus test to a changing world, where oxygen would be the reactive ingredient leading to larger and more complex life forms. As the oxygen production no longer cycled, the oxygen went on to saturate the ocean and then accumulated in the Earth’s atmosphere eventually to the levels we have today.

    7
    Banded iron formation at Karajini. (Nick Siegler, NASA-JPL/Caltech)

    After a day of looking down at rocks and spinifex it was both a relief and a joy to look up at the glorious Western Australian night sky. Far away from the light pollution of modern cities, each night would greet us with an awe-inspiring starlit sky. It never got old to remember we are part of a vast network of stars suspended in an infinite space.

    The nights would start with the appearance of Venus well before sundown followed shortly by the innermost planet Mercury and then Jupiter and Saturn. It didn’t take long after sunset to see the renowned Southern Cross. Mars joined the evening as well, perfectly appearing on the arc called the ecliptic.

    But nothing stirred the group more than the emergence of the swath of stars of the Milky Way, the disk of our home galaxy where its spiral arms all lie. The nights would be so clear that one could actually see the dark clouds of gas and dust that block large portions of the galaxy’s stars from shining through. We partook in the well-known tradition connecting individual points of light to form exotic creatures like scorpions and centaurs. But we also we followed the inverted approach of the Aborigines and connected the dark patches. Only then did we see the emu of the Milky Way. I would never have thought of connecting the darkness.

    The night sky appeared even more special knowing that each of its stellar members likely host planetary systems like our own. How many of them host life? Maybe even civilizations? The numbers are in their favor.

    At the half-way point of our trip we hiked to an ancient granite region in the red rocks of the Pilbara which contain the world’s largest concentration of Pleistocene rock art also known as petroglyphs. These etchings are believed to be 6,000 to 20, 000 years old.

    The artists used no pigments, but rather rocks to pound/chisel shapes into the desert varnish, a thin dark film (possibly of microbial origin) that typically covers exposed rock surfaces in hyper arid regions. We came across many stylized male and female figures with highlighted genitalia as well as animals such as emus and kangaroos. Little is known about the people who created these art works. They left no clues to their origin or fate.

    8
    Rock art by aboriginal people done 6,000 to 20,000 years ago. The shapes were etched into an existing varnish on the rock. (Nick Siegler, NASA-JPL/Caltech)

    Pilbara is also where the oldest mineral on Earth –a zircon dated at 4.4 billion years old — was discovered four years ago in the Jack Hills region. Because of the geological history of the region, it is a frequent (if hardscrabble) site where many geologists and geochemists specializing in ancient Earth do their work.

    In the last several days of the tour we encountered ever-increasing older evidence of stromatolites extending out to circa 3.5 billion years, about 75% of the history of the Earth. I expected the quality of the stromatolites to degrade as we went back in time and it looked like I was right until I saw a remarkably large rock in a locality called the Strelley Pool Formation. The rock measuring approximately 1.5 meters in all three directions gave a rare view of ancient stromatolites from all sides and an unequivocal interpretation of past life.

    The shapes of the embedded rocks formed by the microbial mats from the top view clearly show the elliptical areas where the bacteria inched upwards to acquire sunlight. Regions between the conical stromatolites were filled in by carbonate sediments in ancient shallow waters. These were later chemically altered to silica-rich rocks through alteration and etching of minerals by fluids. Silicified rocks are very weather-resistant, making them a great medium to preserve fossils for billions of years.

    The side views of the stromatolite-laden rock revealed the expected conical layered shapes we saw in younger rocks (and in the living stromatolites of Shark Bay). Everything we had learned about stromatolite structures was clearly visible in this circa 3.43 billion year old example. It is astounding to realize that complex phototrophic (light-eating) organisms, even if not yet oxygen producing, were around during the deposition of the Strelley Pool Formation.

    9
    Detail of Strelley Pool stromatolite fossil. (Nick Siegler, NASA-JPL/Caltech)

    It is not unreasonable to speculate that the earliest life forms are even older by perhaps a few more hundred million years or so. There is evidence for even more ancient stromatolites in Greenland (3.7 billion years old) and isotope carbon evidence, with considerable controversy, in Nuvvuagittuq greenstone belt in northern Quebec, Canada (4.28 billion years old). Hence, life on Earth may have emerged within 500 million years from its formation. That is astonishingly rapid.

    Was Earth an exception or the rule? What does that say for possible life on exoplanets?

    Our tour came to an end on July 11. We had traveled over 1,600 miles through Australia’s outback, from Western Australia’s biggest city Perth, all the way up to Port Hedland at the north coast. We were privileged to see the country in ways that very few people get a chance to, and to be steeped in the multidisciplinary sciences of astrobiology while seeing some of its iconic ground.

    I had seen some of the earliest evidence for life and the pivotal effect it had on our environment. For those 10 days I learned what it was like to be a time traveler.

    See the full article here .


    five-ways-keep-your-child-safe-school-shootings

    Please help promote STEM in your local schools.

    Stem Education Coalition

    About Many Worlds

    There are many worlds out there waiting to fire your imagination.

    Marc Kaufman is an experienced journalist, having spent three decades at The Washington Post and The Philadelphia Inquirer, and is the author of two books on searching for life and planetary habitability. While the “Many Worlds” column is supported by the Lunar Planetary Institute/USRA and informed by NASA’s NExSS initiative, any opinions expressed are the author’s alone.

    This site is for everyone interested in the burgeoning field of exoplanet detection and research, from the general public to scientists in the field. It will present columns, news stories and in-depth features, as well as the work of guest writers.

    About NExSS

    The Nexus for Exoplanet System Science (NExSS) is a NASA research coordination network dedicated to the study of planetary habitability. The goals of NExSS are to investigate the diversity of exoplanets and to learn how their history, geology, and climate interact to create the conditions for life. NExSS investigators also strive to put planets into an architectural context — as solar systems built over the eons through dynamical processes and sculpted by stars. Based on our understanding of our own solar system and habitable planet Earth, researchers in the network aim to identify where habitable niches are most likely to occur, which planets are most likely to be habitable. Leveraging current NASA investments in research and missions, NExSS will accelerate the discovery and characterization of other potentially life-bearing worlds in the galaxy, using a systems science approach.
    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 8:00 am on March 9, 2018 Permalink | Reply
    Tags: , , , , Photosynthesis   

    From astrobio.net: “Photosynthesis originated a billion years earlier than we thought, study shows” 

    Astrobiology Magazine

    Astrobiology Magazine

    Mar 7, 2018
    https://www.elsevier.com

    1
    This plate is a culture of Synechocystis sp. PCC 6803, a type of unicellular Cyanobacteria. Credit: Elsevier

    Ancient microbes may have been producing oxygen through photosynthesis a billion years earlier than we thought, which means oxygen was available for living organisms very close to the origin of life on earth. In a new article in Heliyon, a researcher from Imperial College London studied the molecular machines responsible for photosynthesis and found the process may have evolved as long as 3.6 billion years ago.

    The author of the study, Dr. Tanai Cardona, says the research can help to solve the controversy around when organisms started producing oxygen – something that was vital to the evolution of life on earth. It also suggests that the microorganisms we previously believed to be the first to produce oxygen – cyanobacteria – evolved later, and that simpler bacteria produced oxygen first.

    “My results mean that the process that sustains almost all life on earth today may have been doing so for a lot longer than we think,” said Dr. Cardona. “It may have been that the early availability of oxygen was what allowed microbes to diversify and dominate the world for billions of years. What allowed microbes to escape the cradle where life arose and conquer every corner of this world, more than 3 billion years ago.”

    Photosynthesis is the process that sustains complex life on earth – all of the oxygen on our planet comes from photosynthesis. There are two types of photosynthesis: oxygenic and anoxygenic. Oxygenic photosynthesis uses light energy to split water molecules, releasing oxygen, electrons and protons. Anoxygenic photosynthesis use compounds like hydrogen sulfide or minerals like iron or arsenic instead of water, and it does not produce oxygen.

    2
    This image is the crystal structure of Photosystem I (PDB ID: 1JB0). Credit: Elsevier

    Previously, scientists believed that anoxygenic evolved long before oxygenic photosynthesis, and that the earth’s atmosphere contained no oxygen until about 2.4 to 3 billion years ago. However, the new study suggests that the origin of oxygenic photosynthesis may have been as much as a billion years earlier, which means complex life would have been able to evolve earlier too.

    Dr. Cardona wanted to find out when oxygenic photosynthesis originated. Instead of trying to detect oxygen in ancient rocks, which is what had been done previously, he looked deep inside the molecular machines that carry out photosynthesis – these are complex enzymes called photosystems. Oxygenic and anoxygenic photosynthesis both use an enzyme called Photosystem I. The core of the enzyme looks different in the two types of photosynthesis, and by studying how long ago the genes evolved to be different, Dr. Cardona could work out when oxidative photosynthesis first occurred.

    He found that the differences in the genes may have occurred more than 3.4 billion years ago – long before oxygen was thought to have first been produced on earth. This is also long before cyanobacteria – microbes that were thought to be the first organisms to produce oxygen – existed. This means there must have been predecessors, such as early bacteria, that have since evolved to carry out anoxygenic photosynthesis instead.

    “This is the first time that anyone has tried to time the evolution of the photosystems,” said Dr. Cardona. “The result hints towards the possibility that oxygenic photosynthesis, the process that have produced all oxygen on earth, actually started at a very early stage in the evolutionary history of life – it helps solve one of the big controversies in biology today.”

    One surprising finding was that the evolution of the photosystem was not linear. Photosystems are known to evolve very slowly – they have done so since cyanobacteria appeared at least 2.4 billion years ago. But when Dr. Cardona used that slow rate of evolution to calculate the origin of photosynthesis, he came up with a date that was older than the earth itself. This means the photosystem must have evolved much faster at the beginning – something recent research suggests was due to the planet being hotter.

    “There is still a lot we don’t know about why life is the way it is and how most biological process originated,” said Dr. Cardona. “Sometimes our best educated guesses don’t even come close to representing what really happened so long ago.”

    Dr. Cardona hopes his findings may also help scientists who are looking for life on other planets answer some of their biggest questions.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    NASA

     
c
Compose new post
j
Next post/Next comment
k
Previous post/Previous comment
r
Reply
e
Edit
o
Show/Hide comments
t
Go to top
l
Go to login
h
Show/Hide help
shift + esc
Cancel
%d bloggers like this: