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    Folding protein-mimetic shapes assisting in detecting, decontaminating chem-bio agents

    Structural Details of a  Peptoid Nanosheet

    Courtesy Photo | Structural details of a peptoid nanosheet revealed. (a) Atomic structure of the...... read more read more



    Courtesy Story

    Defense Threat Reduction Agency's Chemical and Biological Technologies Department

    FORT BELVOIR, Va. - Protein-mimetic polymers, constructed from more stable chemical building blocks and can fold into protein-like shapes capable of recognizing threats, are being created by research managed and funded by the Defense Threat Reduction Agency’s Joint Science and Technology Office.

    This is being done because modern warfighters currently cannot accurately detect and decontaminate deadly chemical and biological agents under harsh conditions. In order to fill this capability gap, new biomaterials are needed, ones that exhibit the specificity of biomacromolecules while being more durable and withstanding long periods without refrigeration or water.

    A promising route to protein-mimetic materials capable of complex functions, such as molecular recognition, is provided by sequence-defined peptoid polymers, structural relatives of polypeptides. Peptoids, which are relatively non-toxic and resistant to degradation, can fold into defined structures through sequence-dependent interactions.

    However, the range of possible structures accessible to peptoids and other biomimetics unknown, and current ability to design hierarchical protein-like architectures from these polymers is limited.

    To overcome this problem, JSTO’s basic research effort aims to translate the rules of nature to manufacture protein-like structures. This effort, led by Dr. Ilya Elashvili, a chemical and biological technologies program manager at DTRA, and performed by teams led by Dr. Ronald N. Zuckermann and Dr. Stephen Whitelam at the Molecular Foundry at Lawrence Berkeley National Laboratory, resulted in the clarification of the atomic structure of a nanosheet, a recently-discovered peptoid nanomaterial.

    Through synthesis, imaging, scattering and simulation research methods, researchers discovered that nanosheets are free-floating planar assemblies, which are only two molecules thick, but contain extended microns in their lateral dimensions. Nanosheets are promising candidates for molecular sensors because they possess a large surface area and a high degree of order. They can also be decorated with protein-like elements to enable specific binding to molecular targets that could be harmful to the warfighter.

    Additionally, the team uncovered a new building principle that allows the nanosheet to exist. The research suggested new ways to design biomimetic structures using design principles other than those nature offers. More information is in the “Peptoid Nanosheets Exhibit a New Secondary Structure Motif” article published in Nature.

    The research team partnered with the National Energy Research Scientific Computing Center to utilize supercomputers to customize the peptoid force field developed earlier within the program and to determine the atomic-resolution structure of nanosheets.

    The combination of simulation and experimental methods also allowed the team to identify the building principles for the nanosheet. While nature’s regular protein structures are built in general from protein backbones whose individual units possess the same kind of twist thus creating a bend, the polymers in the peptoid nanosheets twist back and forth along their length, allowing them to remain straight and untwisted.

    Untwisted polymers can be tiled in two dimensions to create the extended flat nanosheets, which have no natural counterpart. The authors refer to this new structural motif as the Sigma strand, in an analogy to the alpha helix and beta sheet found in proteins. The Sigma strand is a fundamental molecular building unit upon which larger and more complex nanoscale structures can be built. Soon it will be possible to design atomically-defined protein-like architectures that can exhibit specific molecular recognition and catalysis.

    Discovery of this new structure opens the door to engineering binding sites for specific analytes into nanosheets, potentially permitting catalytic function. Furthermore, simulations show nanosheets to be water-porous, indicating their potential use as selective membranes. Such materials will find utility in molecular sensors for the warfighter, as well as catalysts that can neutralize harmful chemical or biological agents.



    Date Taken: 11.30.2015
    Date Posted: 12.07.2015 17:36
    Story ID: 183759
    Location: FORT BELVOIR, VA, US 

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