From Techniche Universitat Munchen: “Volcanoes under pressure”

Techniche Universitat Munchen

From Techniche Universitat Munchen

13.11.2019
Prof. Dr. H. Albert Gilg
Technical University of Munich
Professorship for Engineering Geology
agilg@tum.de

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The volcano Merapi on the island Java in Indonesia. Image: iStock_mazzzur

Researchers unlock the secret of explosive volcanism.

When will the next eruption take place? Examination of samples from Indonesia’s Mount Merapi show that the explosivity of stratovolcanoes rises when mineral-rich gases seal the pores and microcracks in the uppermost layers of stone. These findings result in new possibilities for the prediction of an eruption.

Mount Merapi on Java is among the most dangerous volcanoes in the world. Geoscientists have usually used seismic measurements which illustrate underground movements when warning the population of a coming eruption in time.

An international team including scientists from the Technical University of Munich (TUM) has now found another indication for an upcoming eruption in the lava from the peak of Mount Merapi: The uppermost layer of stone, the “plug dome”, becomes impermeable for underground gases before the volcano erupts.

“Our investigations show that the physical properties of the plug dome change over time,” says Prof. H. Albert Gilg from the TUM Professorship for Engineering Geology . “Following an eruption the lava is still easily permeable, but this permeability then sinks over time. Gases are trapped, pressure rises and finally the plug dome bursts in a violent explosion.”

Mount Merapi as a model volcano

Using six lava samples, one from an eruption of Mount Merapi in 2006, the others from the 1902 eruption – the researchers were able to ascertain alterations in the stone. Investigation of pore volumes, densities, mineral composition and structure revealed that permeability dropped by four orders of magnitude as stone alteration increased. The cause is newly formed minerals, in particular potassium and sodium aluminum sulfates which seal the fine cracks and pores in the lava.

The cycle of destruction

Computer simulations confirmed that the reduced permeability of the plug dome was actually responsible for the next eruption. The models show that a stratovolcano like Mount Merapi undergoes three phases: First, after an eruption when the lava is still permeable, outgassing is possible; in the second phase the plug dome becomes impermeable for gases, while at the same time the internal pressure continuously increases; in the third phase the pressure bursts the plug dome.

Photographs of Mount Merapi from the period before and during the eruption of May 11, 2018 support the three-phase model: The volcano first emitted smoke, then seemed to be quiet for a long time until the gas found an escape and shot a fountain of ashes kilometers up into the sky.

“The research results can now be used to more reliably predict eruptions,” says Gilg. “A measurable reduction in outgassing is thus an indication of an imminent eruption.”

Mount Merapi is not the only volcano where outgassing measurements can help in the timely prediction of a pending eruption. Stratovolcanoes are a frequent source of destruction throughout the Pacific. The most famous examples are Mount Pinatubo in the Philippines, Mount St. Helens in the western USA and Mount Fuji in Japan.

Science article:
Hydrothermal alteration of andesitic lava domes can lead to explosive volcanic behaviour
Nature Communications

See the full article here .

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Techniche Universitat Munchin is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “Double strike against tuberculosis”

Techniche Universitat Munchen

Techniche Universitat Munchen

27.12.2017
Prof. Dr. Stephan A. Sieber
Technical University of Munich
Chair of Organic Chemistry II
Lichtenbergstr. 4, 85748 Garching, Germany
Tel.: +49 89 289 13302
stephan.sieber@tum.de

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Dr. Johannes Lehmann (left) and Prof. Stephan A. Sieber examine test results on the antibacterial effect of various substances. (Foto: Christian Fetzer / TUM)

In search of new strategies against life-threatening tuberculosis infections, a team from the Technical University of Munich (TUM), as well as Harvard University and Texas A&M University in the USA have found a new ally. They discovered a substance that interferes with the mycomembrane formation of the bacterium. It is effective even in low concentrations and when combined with known antibiotics their effectiveness is improved by up to 100-fold.

Among the greatest challenges when treating life-threatening tuberculosis infections is the increasing resistance to antibiotics. But the pathogen itself also makes the life of doctors difficult: its dense mycomembrane hampers the effect of many medications.

A team of scientists headed by Stephan A. Sieber, Professor of Organic Chemistry at TU Munich, has discovered a substance that perturbs the formation of this membrane significantly.

The mycomembrane of the tuberculosis pathogen Mycobacterium tuberculosis consists of a lipid double layer that encapsulates the cell wall, forming an exterior barrier. Structural hallmarks are mycolic acids, branched beta-hydroxy fatty acids with two long hydrocarbon chains.

The team hypothesizes that similarly structured beta lactones could “mask” themselves as mycolic acid to enter the mycolic acid metabolic pathways and then block the decisive enzymes.

Helpful disrupter

In the context of an extensive search, the interdisciplinary team of scientists hit the bullseye with the beta lactone EZ120. It does indeed inhibit the biosynthesis of the mycomembrane and kills mycobacteria effectively.

Using enzyme assays and mass spectroscopy investigations, Dr. Johannes Lehmann, a researcher at the Chair of Organic Chemistry II at TU Munich, demonstrated during his doctoral work that the new inhibitor blocks especially the enzymes Pks13 and Ag85, which play a key role in the development of mycomembranes.

EZ120 is effective even in low doses, easily passes the mycomembrane and exhibits only low toxicity to human cells. The combined application of this substance with known antibiotics showed a synergistic effect leading to significantly increased effectiveness.”Vancomycin, a common antibiotic, and EZ120 work together very well,” says Prof. Sieber, who heads the Chair of Organic Chemistry II. “When used together, the dose can be reduced over 100-fold.

“The scientists suspect that disrupting the mycomembrane enables antibiotics to enter the bacteria more easily. This is a new mode of action and might be a starting point for novel tuberculosis therapies.

Publication:

An Antibacterial ß-Lactone Kills Mycobacterium tuberculosis by Disrupting Mycolic Acid BiosynthesisJohannes Lehmann, Tan-Yun Cheng, Anup Aggarwal, Annie S. Park, Evelyn Zeiler, Ravikiran M. Raju, Tatos Akopian, Olga Kandror, James C. Sacchettini, D. Branch Moody, Eric J. Rubin und Stephan A. SieberAngew Chem Int Ed Engl. 2017 Oct 24. http://onlinelibrary.wiley.com/doi/10.1002/anie.201709365/abstract

The research was funded by the German Research Foundation (SFB 749 and Cluster of Excellence “Center for Integrated Protein Science”), the National Institutes of Health (USA) and the German National Academic Foundation (Studienstiftung des Deutschen Volkes). Researchers from the Harvard T.H. Chan School of Public Health and Texas A & M University (College Station, USA) also participated in the research.

See the full article here .

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Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “Breaking Newton’s Law”

Techniche Universitat Munchen

Techniche Universitat Munchen

01.06.2017

Oscillation instead of free fall – Quantum interference leads to surprising results.

In the quantum world, our intuition for moving objects is strongly challenged and may sometimes even completely fail. An international team of physicists of the Universities of Innsbruck, Paris-Sud and Harvard as well as the Technical University of Munich (TUM) has found a quantum particle which shows an intriguing oscillatory back-and-forth motion in a one-dimensional atomic gas instead of moving uniformly.

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A quantum particle performing an intriguing oscillatory back-and-forth motion in a one-dimensional atomic gas. (Image: Florian Meinert / Univ. Innsbruck)

A ripe apple falling from a tree has inspired Sir Isaac Newton to formulate a theory that describes the motion of objects subject to a force. Newton’s equations of motion tell us that a moving body keeps on moving on a straight line unless any disturbing force may change its path.

The impact of Newton’s laws is ubiquitous in our everyday experience, ranging from a skydiver falling in the earth’s gravitational field, over the inertia one feels in an accelerating airplane, to the earth orbiting around the sun.

In the quantum world, however, our intuition for the motion of objects is strongly challenged and may sometimes even completely fail. In the current issue of Science an international team of physicists from Innsbruck, Munich, Paris and Cambridge (USA) describes a quantum particle that shows a completely unexpected behavior.

In a quantum gas the particle does not move like the famous falling apple, but it oscillates. At the heart of this surprising behavior is what physicists call ‘quantum interference’, the fact that quantum mechanics allows particles to behave like waves, which can add up or cancel each other.

Approaching absolute zero temperature

To observe the quantum particle oscillating back and forth the team had to cool a gas of Cesium atoms just above absolute zero temperature and to confine it to an arrangement of very thin “tubes” realized by high-power laser beams. With a special trick, the atoms were made to interact strongly with each other.

At such extreme conditions the atoms form a quantum fluid whose motion is restricted to the direction of the tubes. The physicists then accelerated an impurity atom, which is an atom in a different spin state, through the gas. In our everyday world this corresponds to the apple falling from the tree.

The scientists, however, observed that the quantum wave of the atom was scattered by the other atoms and reflected back again. The result is a striking oscillatory movement. The experiment demonstrates that Newton’s laws cannot be used in the quantum realm.

Quantum fluids sometimes act like crystals

The fact that a quantum-wave may get reflected into certain directions has been known since the early days of the development of the theory of quantum mechanics. For example, electrons reflect at the regular pattern of solid crystals, such as a piece of metal. This effect is termed ‘Bragg-scattering’.

However, the surprise in the experiment performed in Innsbruck was that no such crystal was present for the impurity to reflect off. Instead, it was the gas of atoms itself that provided a type of hidden order in its arrangement, a property that physicist dub ‘correlations’.

The publication has demonstrated how these correlations in combination with the wave-nature of matter determine the motion of particles in the quantum world and lead to novel and exciting phenomena that counteract the experiences from our daily life.

Understanding fundamental processes in electronics components

“Understanding the oddity of quantum mechanics is also relevant in a broader scope,” says Michael Knap, Professor for Collective Quantum Dynamics at the Technical University of Munich. “It might help to understand and optimize fundamental processes in electronics components, or even transport processes in complex biological systems.”

The research was funded by the European Science Council (ERC), the Austrian Science Fund (FWF), the National Science Foundation (NSF) and the US Air Force’s Office of Scientific Research (AFOSP), the Alexander von Humboldt Foundation, the Max Planck Institute for Quantum Optics and the TUM Institute for Advanced Study. In addition to the Walter Schottky Institute of the TU Munich, the Center for Quantum Physics of the University of Innsbruck, the Laboratoire de Physique Théorique et Modèles Statistiques of the University of Paris-Sud and the Physics Department of the Harvard University (Cambridge, Massachusetts, USA) were involved in the research work.

See the full article here .

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Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “16.2 million Euros for neutron and positron research”

Techniche Universitat Munchen

Techniche Universitat Munchen

28.08.2016
Desk:
Andrea Voit (FRM2)

S. Reiffert (TUM)
reiffert@zv.tum.de

The German Federal Ministry of Education and Research (BMBF) has given 13.5 million Euros to fund a number of projects at the Heinz Maier-Leibnitz Zentrum (MLZ). The projects are to be realized by ten different universities over the next three years, including seven projects at the Technical University of Munich (TUM). The Ministry has also given 2.7 million Euros to support the integration of instruments in the new Neutron Guide Hall East at the Heinz Maier-Leibnitz research neutron source (FRM II).

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In the future a combination of x-ray and neutron radiation will make it possible for the tomography system ANTARES to generate even better interior images of batteries. (Photo: Bernhard Ludewig)

The Maier-Leibnitz Zentrum, a partnership between the Technical University of Munich (TUM) and the Helmholtz Centers in Jülich and Geesthacht, gives scientists access to the neutron and positron instruments at the research neutron source of the Heinz Maier-Leibnitz Zentrum (FRM II) in Garching. The BMBF focus program “Condensed Matter Research with Large Scale Facilities” will support a total of 19 research projects at the MLZ until 2019.

Three scientific instruments will be completed using this funding over the course of the next three years:
SAPHiR, the high-pressure press of the Bavarian Research Institute of Experimental Geochemistry and Geophysics in Bayreuth (BGI) is capable of reproducing pressures and temperatures typical of the earth’s interior for the investigation of their effects on geological samples. The neutrons will provide highly precise measurements of stone structures and will thus for example enable analysis of stone folding, while at the same time helping to develop new magnetic storage media.

At the RWTH Aachen University’s high-intensity neutron time of flight diffractometer POWTEX, the funding will go towards the construction of an innovative wide-area neutron detector. RWTH Aachen University and Göttingen University (Georg-August-Universität) received the funding necessary to develop the associated software.

Highly polarized neutrons will be realized using the funding for the University of Cologne’s cold three-axis spectrometer KOMPASS. This will enable the investigation of weak magnetic orderings and complex magnetic systems in order to achieve higher storage densities in future PCs.

Faster measurements with BAMBUS – ERWIN supplements RESI in battery tests

The Technical University of Dresden’s multi-detector system BAMBUS at the three-axis spectrometer PANDA will use the financial support to increase the speed with which the position and extent of unknown excitations can be found. This improves the efficiency of investigations on potential materials for quantum computers and innovative superconductors.

The Karlsruhe Institute of Technology is in charge of two additional projects with the goal of observing on a completely non-destructive basis the molecular processes that occur when charging and discharging batteries in order to create higher-performance and longer-lasting batteries: Here the single crystal diffractometer RESI will be extended to include the option ERWIN (Energy Research WIth Neutrons) and the instrument NECTAR for radiography and tomography with thermal neutrons.

With its project involving the hot single crystal diffractometer HEIDI, the RWTH Aachen University intends to enable investigation of samples ten times smaller than usually viable with neutrons – significantly less than one cubic millimeter – and to provide anvil cells for high-pressure experiments.

Several professors at the TUM are creating new measurement options using neutrons
The BMBF is also supporting six projects at the TUM Physics department:

Alloys for new high-performance materials for gas turbines have to withstand very high temperatures of up to 1200°C while retaining tensile strength and staying pressure-resistant. Dr. Ralph Gilles is building a high-temperature oven and a cooling unit to test these alloys with neutrons.

Prof. Peter Böni and Dr. Robert Georgii are constructing a module that can be used with various different instruments and makes it possible to measure magnetic and structural excitations at small scattering angles even in strong magnetic fields.

Prof. Christian Pfleiderer is planning an extension for the neutron spin echo spectrometer RESEDA that will increase neutrons intensity in strong magnetic fields with ultra-high resolution.

In the future a combination of x-ray and neutron radiation will make it possible for the tomography system ANTARES to generate even better interior images of batteries. The project, dubbed NeuRoFast, is coordinated by Prof. Franz Pfeiffer.

Prof. Bastian Märkisch is further enhancing the instrument PGAA in order to make even higher resolution measurements of deeper layers of lithium in batteries and boron in photovoltaic cells containing silicon.

As a result of the BMBF funding awarded to Prof. Peter Müller-Buschbaum (TUM), the time of flight spectrometer TOFTOF will receive a new sample environment making it possible for example to observe bacterial proteins during photosynthesis.

Shorter measurement periods for positrons

RWTH Aachen University is expanding the biological laboratory to enable able scientists to investigate proteins in addition to neutrons with other spectroscopic instruments at the MLZ. In the future investigation of the three-dimensional ordering of nano-particles will be possible with the software product BornAgain, enhanced by the FAU (Friedrich-Alexander-Universität) Erlangen-Nuremberg.

In addition to neutron instruments, the world’s most intensive positron source is also being expanded at the FRM II with the BMBF funds.

Among other things the Bundeswehr University Munich (UniBwM) is expanding the scanning positron microscope and pulsed positron beam to make more measurements with electron anti-particles possible within a shorter period of time.

Dr. Christoph Hugenschmidt of the Technical University of Munich is developing a completely innovative positron instrument for high-precision determination of surface structures and the three-dimensional distribution of crystal defects.

“Unprecedented spectrum of life and health sciences”

Prof. Winfried Petry, scientific director of the FRM II and MLZ, comments: “The joint BMBF research is an ideal way to integrate university research in the utilization of the MLZ. At the same time we can attract the most highly coveted measurement guests in the world with new construction and continuing improvement of scientific instruments.”

Prof. Brückel, director of the Jülich Centre for Neutron Scattering (JCNS) and scientific director at the MLZ, adds: “In the projects supported, the Heinz Maier-Leibnitz Zentrum covers an unprecedented spectrum of life and health sciences ranging from protein research to nano-sciences and engineering sciences, all the way to energy research for battery systems.”

The Heinz Maier-Leibnitz Zentrum (MLZ) is a leader in cutting-edge research with neutrons and positrons. As a facility for scientific users at the FRM II research neutron source, the MLZ offers a unique selection of approximately 30 high-performance neutron measuring instruments to visiting scientists. The MLZ is a partnership of the Technical University of Munich (TUM), the Forschungszentrum Jülich and the Helmholtz-Zentrum Geesthacht Center for Materials and Coastal Research (HZG). This partnership is financially supported by the German Federal Ministry of Education and Research (BMBF) and the Bavarian State Ministry for Education and Culture, Science and the Arts. Other universities and the Max-Planck-Gesellschaft are also involved with the measuring instruments of the MLZ.

The research neutron source Heinz Maier-Leibnitz (FRM II) provides neutron beams for research, industry and medicine. It is operated by the Technical University of Munich (TUM) and financed by the Bavarian State Ministry for Education and Culture Science and the Arts.

See the full article here .

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Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “Meteorite Impact on a Nano Scale”

Techniche Universitat Munchen

Techniche Universitat Munchen

2016-08-29
Prof. Friedrich Aumayr
Institute of Applied Physics
TU Wien
Wiedner Hauptstraße 8-10, 1040 Wien
T: +43-1-58801-13430
friedrich.aumayr@tuwien.ac.at

Dipl.-Ing. Elisabeth Gruber
Institute of Applied Physics
TU Wien
Wiedner Hauptstraße 8-10, 1040 Wien
T: +43-1-58801-13435
elisabeth.gruber@tuwien.ac.at

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Elisabeth Gruber in the lab at TU Wien

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Nanostructures on a crystal after ion bombardment: Trenches with nanohillocks on either side are created. At the impact site, a particularly large nanohillock is formed.

Intricate nanostructures can be created on crystal surfaces by hitting them with high energy ions. Scientists from TU Wien (Vienna) can now explain these remarkable phenomena.

A meteorite impacting the earth under a grazing angle of incidence can do a lot of damage; it may travel a long way, carving a trench into the ground until it finally penetrates the surface. The impact site may be vaporized, there can be large areas of molten ground. All that remains is a crater, some debris, and an extensive trail of devastation on both sides of the impact site.

Hitting a surface with high-energy, heavy ions has quite similar effects – only on a much smaller scale. At TU Wien (Vienna), Prof. Friedrich Aumayr and his team have been studying the microscopic structures which are formed when ions are fired at crystals at oblique angles of incidence.

Trenches and Ridges

“When we take a look at the crystal surface with an atomic force microscope, we can clearly see the similarities between ion impacts and meteorite impacts”, says Elisabeth Gruber, PhD-student in Friedrich Aumayrs team. “At first the projectile, scratching across the surface at a grazing angle, digs a trench into the crystal surface, which can be hundreds of nanometers long. Extensive ridges appear on either side of the trench, consisting of tiny structures called nanohillocks.” When the projectile ultimately enters the crystal and disappears, an especially large hillock is created at the impact site. Beyond that, the ion keeps moving below the surface, until it finally comes to a halt.

This may sound simple and obvious, as if high energy ions just behaved like tiny, electrically charged bullets. But in fact, it is not at all self-evident that objects on a nano scale behave like macroscopic objects do. When atoms exchange energy, quantum physics always plays an important role.

“When the high-energy ions interact with crystal surfaces – calcium fluoride, in our case – many different physical effects have to be taken into account”, says Friedrich Aumayr. “Electrons can change their energy state, they can exchange energy with atoms around them and excite vibrations in the crystal lattice, the so-called phonons. We have to carefully consider all these effects when we want to understand how the nanostructures on the crystal surface are created.”

Melting and Evaporation

In order to understand the mechanism leading to the nano-trenches and hillocks, the team developed extensive computer simulations, together with colleagues from Germany. “That way we can determine, how much different parts of the crystal surface are heated up”, says Elisabeth Gruber. “There are regions which become so hot that the material melts, at certain points it can even evaporate. When we know how large these regions are, we can predict very accurately what the nanostructures on the crystal surface will look like.”

The goal of this line of research is not only to understand how tailored nanostructures can be created. It is also important to find out how different materials are harmed by heavy ion bombardment. “Calcium fluoride is often used as an insulator in semiconductor technology”, says Friedrich Aumayr. “We want our electronics to work, even under extreme conditions, for instance in a satellite which is exposed to cosmic radiation.” When the calcium fluoride layer is riddled with tiny holes, it can cause the device to short circuit and fail. Therefore, it is vital to understand the interaction of crystal surfaces and fast ions.

Original publication:
E. Gruber et al., Swift heavy ion irradiation of CaF2 – from grooves to hillocks in a single ion track 405001 Journal of Physics: Condensed Matter 28 (2016)

See the full article here .

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Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “A look at the molecular quality assurance within cells”

Techniche Universitat Munchen

Techniche Universitat Munchen

25.08.2016
Technical University of Munich
Prof. Dr. Matthias J. Feige
matthias.feige@tum.de
+49-89-28910595
www.cell.ch.tum.de

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A look at the molecular quality assurance within cells. (Illustration: Joshua Stokes, St. Jude Children’s Research Hospital)

Proteins fulfill vital functions in our body. They transport substances, combat pathogens, and function as catalysts. In order for these processes to function reliably, proteins must adopt a defined three-dimensional structure. Molecular “folding assistants”, called chaperones, aid and scrutinize these structuring processes. With participation from the Technical University of Munich (TUM), a team of researchers has now revealed how chaperones identify particularly harmful errors in this structuring process. The findings were published in the scientific journal “Molecular Cell”.

Chaperones are a kind of Technical Inspection Authority for cells. They are proteins that inspect other proteins for quality defects before they are allowed to leave the cell.

If a car does not pass its technical inspection, it implies that it has severe defects that could lead to serious accidents. If a protein folds into a faulty structure, this may lead to serious diseases. Examples of these are neurodegenerative disorders such as Alzheimer’s, but also metabolic diseases such as cystic fibrosis and diabetes.

Matthias Feige, professor for cellular protein biochemistry at the TUM, worked within a team headed by Linda Hendershot at St. Jude Children’s Research Hospital in Memphis/TN, USA, to investigate how chaperones identify structurally flawed proteins. In the study, the scientists focused on proteins which are produced in a part of the cell called the endoplasmic reticulum. “We are mainly interested in cellular protein folding”, explains Feige. “How the self-organization of proteins occurs at the molecular level – and how cells identify errors in this process – is a truly fascinating question.”

Defective proteins need to be eliminated by the cell

The endoplasmic reticulum consists of a network of hollow spaces and tubules. It is specialized in protein folding and the quality control for this process, and a third of all human proteins are produced here. Just like in any production process, errors may occur: Proteins form a folding core mostly made up of hydrophobic (water-repellent) amino acids, around which the rest of the protein is able to structure itself. However, if errors occur in the folding process, these hydrophobic areas may not be buried in the core, but instead be exposed on the surface of a protein where they may result in proteins clumping together. This can become hazardous to the cell or the entire organism.

Into the cell via a shuttle

Thus far, scientists knew that chaperones were able to identify general hydrophobic amino acid sequences if they remained exposed on protein surfaces. However, not all proteins which present such sequences should necessarily be degraded. That is because not all proteins with hydrophobic amino acid sequences on the surface are defective. How exactly the cell decides if a protein is so dangerous that it needs to be eliminated remained a mystery.

The researchers developed a new method which made it possible to observe the behavior of chaperones in the living biological system of the cell. To do this, they inserted precisely defined sequences of amino acids, which are the building blocks of proteins, into a shuttle system that transported them into the endoplasmic reticulum within the cell. Via this ingenious trick, they were able to observe, under biologically relevant conditions, which sequences the various chaperones recognized.

Two classes of chaperones

What they discovered was that there existed not only one, but two classes of chaperones in the endoplasmic reticulum, each of which identifies different types of hydrophobic amino acid sequences. Furthermore, the sequences identified by the chaperones of the second class, which are described in this journal article for the first time, form particularly dangerous clumps in the cell. Once they are identified, the proteins possessing them can be eliminated rapidly.

“This is an important piece in the puzzle of how molecular quality control functions”, says Feige. “Follow-up studies will now be required to see how the chaperones recognize their target sequences on a structural level.”

This research is also important for the biotechnological production of proteins, such as antibodies. In order to prevent these pharmaceutical products from being broken down by the body too quickly, biotechnologists can now ensure that the corresponding sequences do not appear on the surface of the proteins.

Publication: Julia Behnke, Melissa J. Mann, Fei-Lin Scruggs, Matthias J. Feige, Linda M. Hendershot, “Members of the Hsp70 Family Recognize Distinct Types of Sequences to Execute ER Quality Control“, Molecular Cell, published online August 18, 2016

See the full article here .

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Technische Universität München (TUM) is one of Europe’s top universities. It is committed to excellence in research and teaching, interdisciplinary education and the active promotion of promising young scientists. The university also forges strong links with companies and scientific institutions across the world. TUM was one of the first universities in Germany to be named a University of Excellence. Moreover, TUM regularly ranks among the best European universities in international rankings.

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From TUM: “Interaction of Earth with supernova remnants lasting for one million years”

Techniche Universitat Munchen

Techniche Universitat Munchen

10.08.2016
Contact
Technical University of Munich
Prof. Dr. Shawn Bishop
Tel.: +49 89 289 12437
shawn.bishop@tum.de

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Starry sky through trees. When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. (Photo: kaalimies / fotolia)

Physicists from the Technical University of Munich (TUM) have succeeded in detecting a time-resolved supernova signal in the Earth’s microfossil record. As the group of Prof. Shawn Bishop could show, the supernova signal was first detectable at a time starting about 2.7 million years ago. According to the researcher’s analyses, our solar system spent one Million years to transit trough the remnants of a supernova.

When massive stars with more than ten solar masses have, at the end of their evolution, consumed all of their nuclear fuel supply, they collapse under their gravity and terminate in so-called core-collapse supernovae. Thereby they eject huge amounts of matter into their surroundings. If a supernova occurs sufficiently close to our solar system, it should leave traces of supernova debris on Earth, in the form of specific radioisotopes.

Among the elemental species known to be produced in these stars, the radioisotope Fe-60 stands out: This radioisotope has no natural, terrestrial production mechanisms; thus, a detection of Fe-60 atoms within terrestrial reservoirs is proof for the direct deposition of supernova material within our solar system.

Increased concentration also found in lunar samples

An excess of Fe-60 was already observed in around two million year old layers of a ferromanganese (FeMn) crust retrieved from the Pacific Ocean and, most recently, in lunar samples. These Fe-60 signals have been attributed to depositions of supernova ejecta. However, due to the slow growth rate of the FeMn crust, the Fe-60 signal had a poor temporal resolution; while lunar regolith cannot record time information because sedimentation does not occur on the moon.

Now for the first time, physicists of the group of Shawn Bishop, TUM Professor on Nuclear Astrophysics, succeeded in discovering a time-resolved supernova signal in the Earth’s microfossil record, residing in biogenically produced crystals from two Pacific Ocean sediment drill cores. The onset of the Fe-60 signal occurs at around 2.7 Million years and is centered at around 2.2 Million years. The signal significantly ends around 1.7 Million years.

“Obviously, the solar system spent on Million years to transit through the debris of a supernova,” says Shawn Bishop, who is also a principal investigator at the Excellence Cluster Universe.

Samples with excellent stratigraphic resolution

To analyse the entire temporal structure of the Fe-60 signal in terrestrial samples, a geological reservoir with an excellent stratigraphic resolution and high Fe-60 sequestration and low Fe mobility is required, which preserves the Fe-60 fluxes nearly so as they were at the time of deposition, apart from Fe-60 radioactive decay.

These conditions are fulfilled in the marine sediments from the Pacific Ocean used in this study. At the time of the Fe-60 deposition, iron-sequestering bacteria that live in the ocean sediments incorporated the Fe-60 within their intracellularly-grown chains of magnetite nanocrystals (Fe3O4). After cell death they have fossilized into microfossils. These sediments have grown with a constant sedimentation rate, preserving the intrinsic temporal shape of the supernova signal. “Nevertheless, the Fe-60 concentration in these fossils is so low that it is detectable only by means of ultrasensitive accelerator mass spectroscopy (AMS)”, says Dr. Peter Ludwig, researcher in the group of Shawn Bishop. At the tandem accelerator at the Maier-Leibnitz Laboratory in Garching the physicists could refine the sensitivity of the method so that this discovery was possible the first time ever.

Supernova event at a distance of at least 300 light years

The most plausible progenitor star that gave rise to this supernova likely originated in the Scorpius-Centaurus OB association, as analyses of its relative motion have shown. Around 2.3 million years ago it was located at a minimum distance of about 300 light years to the solar system. Over the course of the last 10 to 15 million years, a succession of 15 to 20 supernovae has occurred in this star association. This series of massive stellar explosions has produced a largely matter-free cavity in the interstellar medium of a galactic arm of the Milky Way. Astronomers call this cavity, in which our solar system is located, the Local Bubble.

Acknowledgement

In addition to the TUM’s physicists there were also involved: Researchers from the Central Institute for Meteorology and Geodynamics, Geomagnetism and Gravimetry, Vienna, from the TUM Chemistry Department, Elektronenmikroskopie, as well as from the Helmholtz-Zentrum Dresden-Rossendorf, Helmholtz Institute Freiberg for Resource Technology, Dresden.

The research was funded by the German Research Foundation (DFG) and the Excellence Cluster Universe

Original publication

Ludwig et al.: Time resolved 2-million-year-old supernova activity discovered in Earth’s microfossil record
Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1601040113, August 8, 2016

See the full article here .

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