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  • richardmitnick 9:24 pm on January 28, 2016 Permalink | Reply
    Tags: , Covalent and supramolecular polymers in one, Northwestern   

    From Northwestern: “Researchers Develop Completely New Kind of Polymer” 

    Northwestern U bloc

    Northwestern University

    January 28, 2016
    Megan Fellman

    Polymers
    Northwestern University researchers have developed a new hybrid polymer with removable supramolecular compartments, shown in this molecular model. (Credit: Mark E. Seniw, Northwestern University)

    Imagine a polymer with removable parts that can deliver something to the environment and then be chemically regenerated to function again. Or a polymer that can lift weights, contracting and expanding the way muscles do.

    These functions require polymers with both rigid and soft nano-sized compartments with extremely different properties that are organized in specific ways. A completely new hybrid polymer of this type has been developed by Northwestern University researchers that might one day be used in artificial muscles or other life-like materials; for delivery of drugs, biomolecules or other chemicals; in materials with self-repair capability; and for replaceable energy sources.

    “We have created a surprising new polymer with nano-sized compartments that can be removed and chemically regenerated multiple times,” said materials scientist Samuel I. Stupp, the senior author of the study.

    “Some of the nanoscale compartments contain rigid conventional polymers, but others contain the so-called supramolecular polymers, which can respond rapidly to stimuli, be delivered to the environment and then be easily regenerated again in the same locations. The supramolecular soft compartments could be animated to generate polymers with the functions we see in living things,” he said.

    Stupp is director of Northwestern’s Simpson Querrey Institute for BioNanotechnology. He is a leader in the fields of nanoscience and supramolecular self-assembly, the strategy used by biology to create highly functional ordered structures.

    The hybrid polymer cleverly combines the two types of known polymers: those formed with strong covalent bonds and those formed with weak non-covalent bonds, well known as “supramolecular polymers.” The integrated polymer offers two distinct “compartments” with which chemists and materials scientists can work to provide useful features.

    The study will be published in the Jan. 29 issue of Science.

    “Our discovery could transform the world of polymers and start a third chapter in their history: that of the ‘hybrid polymer,’” Stupp said. “This would follow the first chapter of broadly useful covalent polymers, then the more recent emerging class of supramolecular polymers.

    “We can create active or responsive materials not known previously by taking advantage of the compartments with weak non-covalent bonds, which should be highly dynamic like living things. Some forms of these polymers now under development in my laboratory behave like artificial muscles,” he said.

    Polymers get their power and features from their structure at the nanoscale. The covalent rigid skeleton of Stupp’s first hybrid polymer has a cross-section shaped like a ninja star — a hard core with arms spiraling out. In between the arms is the softer “life force” material. This is the area that can be animated, refreshed and recharged, features that could be useful in a range of valuable applications.

    “The fascinating chemistry of the hybrid polymers is that growing the two types of polymers simultaneously generates a structure that is completely different from the two grown alone,” Stupp said. “I can envision this new material being a super-smart patch for drug delivery, where you load the patch with different medications, and then reload it in the exact same compartments when the medicine is gone.”

    Stupp also is the Board of Trustees Professor of Materials Science and Engineering, Chemistry, Medicine and Biomedical Engineering and holds appointments in Northwestern University Feinberg School of Medicine, the McCormick School of Engineering and Applied Science and the Weinberg College of Arts and Sciences.

    Stupp and his research team also discovered that the covalent polymerization that forms the rigid compartment is “catalyzed” by the supramolecular polymerization, thus yielding much higher molecular weight polymers.

    The strongly bonded covalent compartment provides the skeleton, and the weakly bonded supramolecular compartment can wear away or be used up, depending on its function, and then be regenerated by adding small molecules. After the simultaneous polymerizations of covalent and non-covalent bonds, the two compartments end up bonded to each other, yielding a very long, perfectly shaped cylindrical filament.

    To better understand the hybrid’s underlying chemistry, Stupp and his team worked with George C. Schatz, a world-renowned theoretician and a Charles E. and Emma H. Morrison Professor of Chemistry at Northwestern. Schatz’s computer simulations showed the two types of compartments are nicely integrated with hydrogen bonds, which are bonds that can be broken. Schatz is a co-author of the study.

    “This is a remarkable achievement in making polymers in a totally new way — simultaneously controlling both their chemistry and how their molecules come together,” said Andy Lovinger, a materials science program director at the National Science Foundation, which funded this research.

    “We’re just at the very start of this process, but further down the road it could potentially lead to materials with unique properties — such as disassembling and reassembling themselves — which could have a broad range of applications,” Lovinger said.

    The work was supported by the National Science Foundation (grant DMR-1508731), the Department of Energy’s Biomolecular Materials Program (grant DE-FG02-00ER45810) and the Department of Energy’s EFRC Center for Bio-Inspired Energy Science, headquartered at Northwestern and directed by Stupp (grant DE-SC0000989).

    The paper is titled Simultaneous covalent and noncovalent hybrid polymerizations.

    In addition to Stupp and Schatz, other authors of the paper are Zhilin Yu (first author), Faifan Tantakitti, Tao Yu and Liam C. Palmer, all from Northwestern.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
  • richardmitnick 7:39 pm on January 28, 2016 Permalink | Reply
    Tags: , , , Northwestern   

    From Northwestern: “Stellar Parenting: Making New Stars By ‘Adopting’ Stray Cosmic Gases” 

    Northwestern U bloc

    Northwestern University

    January 27, 2016
    No writer credit found

    Globular cluster star field
    Using observations by the Hubble Space Telescope, an international research team, including astronomers from Northwestern and the Kavli Institute for Astronomy and Astrophysics, has for the first time found young populations of stars within globular clusters that have apparently developed courtesy of star-forming gas flowing in from outside of the clusters themselves. Credit: ESA/Hubble and NASA. Acknowledgement: Judy Schmidt (geckzilla.com)

    Among the most striking objects in the universe are glittering, dense swarms of stars known as globular clusters. Astronomers had long thought globular clusters formed their millions of stars in bulk at around the same time, with each cluster’s stars having very similar ages, much like twin brothers and sisters. Yet recent discoveries of young stars in old globular clusters have scrambled this tidy picture.

    Instead of having all their stellar progeny at once, globular clusters can somehow bear second or even third sets of thousands of sibling stars. Now a new study led by researchers at the Kavli Institute for Astronomy and Astrophysics (KIAA) at Peking University, and including astronomers at Northwestern University, the Adler Planetarium and the National Astronomical Observatories of the Chinese Academy of Sciences (NAOC), might explain these puzzling, successive stellar generations.

    Using observations by the Hubble Space Telescope, the research team has for the first time found young populations of stars within globular clusters that have apparently developed courtesy of star-forming gas flowing in from outside of the clusters themselves.

    NASA Hubble Telescope
    NASA/ESA Hubble

    This method stands in contrast to the conventional idea of the clusters’ initial stars shedding gas as they age in order to spark future rounds of star birth.

    The study will be published in the Jan. 28 issue of the journal Nature.

    “This study offers new insight on the problem of multiple stellar populations in star clusters,” said study lead author Chengyuan Li, an astronomer at KIAA and NAOC who also is affiliated with the Chinese Academy of Sciences’ Purple Mountain Observatory.

    “Our study suggests the gaseous fuel for these new stellar populations has an origin that is external to the cluster, rather than internal.”

    In a manner of speaking, globular clusters appear capable of “adopting” baby stars — or at least the material with which to form new stars — rather than creating more “biological” children as parents in a human family might choose to do.

    “Our explanation that secondary stellar populations originate from gas accreted from the clusters’ environments is the strongest alternative idea put forward to date,” said Richard de Grijs, also an astronomer at KIAA and Chengyuan’s Ph.D. advisor. “Globular clusters have turned out to be much more complex than we once thought.”

    Globular clusters are spherical, densely packed groups of stars orbiting the outskirts of galaxies. Our home galaxy, the Milky Way, hosts several hundred. Most of these local, massive clusters are quite old, however, so the KIAA-led research team turned their attention to young and intermediate-aged clusters found in two nearby dwarf galaxies, collectively called the Magellanic Clouds.

    Specifically, the researchers used Hubble observations of the globular clusters NGC 1783 and NGC 1696 in the Large Magellanic Cloud, along with NGC 411 in the Small Magellanic Cloud.

    Scientists routinely infer the ages of stars by looking at their colors and brightnesses. Within NGC 1783, for example, Li, de Grijs and colleagues identified an initial population of stars aged 1.4 billion years, along with two newer populations that formed 890 million and 450 million years ago.

    What is the most straightforward explanation for these unexpectedly differing stellar ages? Some globular clusters might retain enough gas and dust to crank out multiple generations of stars, but this seems unlikely, said study co-author Aaron M. Geller of Northwestern University and the Adler Planetarium in Chicago.

    “Once the most massive stars form, they are like ticking time bombs, with only about 10 million years until they explode in powerful supernovae and clear out any remaining gas and dust,” Geller said. “Afterwards, the lower-mass stars, which live longer and die in less violent ways, may allow the cluster to build up gas and dust once again.”

    The KIAA-led research team proposes that globular clusters can sweep up stray gas and dust they encounter while moving about their respective host galaxies. The theory of newborn stars arising in clusters as they “adopt” interstellar gases actually dates back to a 1952 paper. More than a half-century later, this once speculative idea suddenly has key evidence to support it.

    In the study, the KIAA researchers analyzed Hubble observations of these star clusters, and then Geller and his Northwestern colleague Claude-André Faucher-Giguère carried out calculations that show this theoretical explanation is possible in the globular clusters this team studied.

    “We have now finally shown that this idea of clusters forming new stars with accreted gas might actually work,” de Grijs said, “and not just for the three clusters we observed for this study, but possibly for a whole slew of them.”

    Future studies will aim to extend the findings to other Magellanic Cloud as well as Milky Way globular clusters.

    The research is funded, in part, by the National Science Foundation.

    The title of the paper is Formation of new stellar populations from gas accreted by massive young star clusters.

    In addition to Li, de Grijs, Geller and Faucher-Giguère, other authors of the paper include Licai Deng, Yu Xin and Yi Hu, all from the Chinese Academy of Science’s National Astronomical Observatories in Beijing.

    Geller, an NSF Astronomy and Astrophysics Postdoctoral Fellow, and Faucher-Giguère, an assistant professor of physics and astronomy, are in Northwestern’s Weinberg College of Arts and Sciences and are members of the Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). Geller also is currently at the Adler Planetarium in Chicago and previously was with the department of astronomy and astrophysics at the University of Chicago at the time of the study.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
  • richardmitnick 8:59 pm on January 25, 2016 Permalink | Reply
    Tags: , , Northwestern, Researchers Pinpoint Place Where Cancer Cells May Begin, The fruitful fruitfly   

    From Northwestern: “Researchers Pinpoint Place Where Cancer Cells May Begin” 

    Northwestern U bloc

    Northwestern University

    January 20, 2016
    Megan Fellman

    Fruitfly eye signals about cancer
    The fruit fly’s eye is an intricate pattern of many different specialized cells, and scientists use it as a workhorse to study what goes wrong in human cancer. In a new study of the fly’s eye, Northwestern University researchers have gained insight into how developing cells normally switch to a restricted, or specialized, state and how that process might go wrong in cancer. (Credit: Northwestern University)

    Cancer cells are normal cells that go awry by making bad developmental decisions during their lives. In a study involving the fruit fly equivalent of an oncogene implicated in many human leukemias, Northwestern University researchers have gained insight into how developing cells normally switch to a restricted, or specialized, state and how that process might go wrong in cancer.

    The fruit fly’s eye is an intricate pattern of many different specialized cells, such as light-sensing neurons and cone cells. Because flies share with humans many of the same cancer-causing genes, scientists use the precisely made compound eye of Drosophila melanogaster (the common fruit fly) as a workhorse to study what goes wrong in human cancer.

    A multidisciplinary team co-led by biologist Richard W. Carthew and engineer Luís A.N. Amaral studied normal cell behavior in the developing eye. The researchers were surprised to discover that the levels of an important protein called Yan start fluctuating wildly when the cell is switching from a more primitive, stem-like state to a more specialized state. If the levels don’t or can’t fluctuate, the cell doesn’t switch and move forward.

    “This mad fluctuation, or noise, happens at the time of cell transition,” said Carthew, professor of molecular biosciences in Northwestern’s Weinberg College of Arts and Sciences. “For the first time, we see there is a brief time period as the developing cell goes from point A to point B. The noise is a state of ‘in between’ and is important for cells to switch to a more specialized state. This limbo might be where normal cells take a cancerous path.”

    The researchers also found that a molecular signal received by a cell receptor called EGFR is important for turning the noise off. If that signal is not received, the cell remains in an uncontrolled state.

    By pinpointing this noise and its “off” switch as important points in the normal process of cell differentiation, the Northwestern researchers provide targets for scientists studying how cells can go out of control and transform into cancer cells.

    The study was published as the cover story Jan. 14 by the online life sciences and biomedicine journal eLife.

    The “noisy” protein the Northwestern researchers studied is called Yan in the fly and Tel-1 in humans. (The protein is a transcription factor.) The Tel-1 protein instructs cells to turn into white blood cells; the gene that produces the protein, oncogene Tel-1, is frequently mutated in leukemia.

    The EGFR protein that turns off the noise in flies is called Her-2 in humans. Her-2 is an oncogene that plays an important role in human breast cancer.

    “On the surface, flies and humans are very different, but we share a remarkable amount of infrastructure,” said Carthew, a member of the Robert H. Lurie Comprehensive Cancer Center of Northwestern University. “We can use fruit fly genetics to understand how humans work and how things go wrong in cancer and other diseases.”

    Fruit fly cells are small and closely packed together, making study of them challenging. Carthew and Amaral’s team of biologists, chemical and biological engineers, computer scientists and chemists together figured out how to identify and analyze thousands and thousands of individual cells in the flies’ eyes.

    “In the past, people have built models of regulatory networks that control cell differentiation mostly by genetically perturbing one or two components of the network at a time and then compiling those results into models,” said Amaral, professor of chemical and biological engineering at the McCormick School of Engineering. “We instead measured the retina as it developed and found the unexpected behavior of the key regulatory factors Yan and EGFR.”

    Nicolás Peláez, first author of the study and a Ph.D. candidate in interdisciplinary biological sciences working with Amaral and Carthew, built new tools to study this strange feature of noise in developing flies. His methods enabled the researchers to easily measure both the concentration of the Yan protein and its fluctuation (noise).

    It takes 15 to 20 hours for a fruit fly cell to go from being an unrestricted cell to a restricted cell, Carthew said. Peláez determined the Yan protein is noisy, or fluctuating, for six to eight of those hours.

    “Studying the dynamics of molecules regulating fly-eye patterning can inform us about human disease,” Peláez said. “Using model organisms such as fruit flies will help us understand quantitatively the basic biological principles governing differentiation in complex animals.”

    The Department of Energy (grant DE-NA0002520) and the National Institutes of Health (grants P50GM081892, R01GM80372 and R01GM077581) supported the research.

    The paper is titled Dynamics and Heterogeneity of a Fate Determinant During Transition Towards Cell Differentiation.

    In addition to Carthew, Amaral and Peláez, other authors are Bao Wang and Aggelos K. Katsaggelos, of Northwestern; Arnau Gavalda-Miralles and Heliodoro Tejedor Navarro, of the Howard Hughes Medical Institute; and Herman Gudjonson, Ilaria Rebay and Aaron R. Dinner, of the University of Chicago.

    See the full article here .

    Please help promote STEM in your local schools.

    STEM Icon

    Stem Education Coalition

    Northwestern South Campus
    South Campus

    On May 31, 1850, nine men gathered to begin planning a university that would serve the Northwest Territory.

    Given that they had little money, no land and limited higher education experience, their vision was ambitious. But through a combination of creative financing, shrewd politicking, religious inspiration and an abundance of hard work, the founders of Northwestern University were able to make that dream a reality.

    In 1853, the founders purchased a 379-acre tract of land on the shore of Lake Michigan 12 miles north of Chicago. They established a campus and developed the land near it, naming the surrounding town Evanston in honor of one of the University’s founders, John Evans. After completing its first building in 1855, Northwestern began classes that fall with two faculty members and 10 students.
    Twenty-one presidents have presided over Northwestern in the years since. The University has grown to include 12 schools and colleges, with additional campuses in Chicago and Doha, Qatar.

    Northwestern is recognized nationally and internationally for its educational programs.

     
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