Biologically-derived proteins and peptides assemble to yield complex structures and functions (e.g. viruses). In contrast, much simpler assemblies typically result (e.g. spherical micelles) when synthetic macromolecules are employed. The sophistication of protein and peptide structures is possible because of their (1) versatile, heteropolymeric chemistry (i.e., amino acid sequences), (2) defined secondary structures (i.e. molecular conformations such as beta-sheets, alpha-helices, and other turns and coils) that provide for specific, local shapes to display amino-acid functionality,(3) well-defined, intramolecular, folded conformations (tertiary structure), and (4) well-ordered quaternary, or intermolecular, structure through the assembly of multiple polypeptide chains. As in nature, the potential exists to build new complex structures and functions via the careful choice of the sequence of amino acids in a polypeptide. This DMREF effort will elucidate fundamental principles and methods for the design of nonnatural one- and two-dimensional polypeptide assemblies. The solution assembly of these designed peptides will be characterized experimentally, and they will be functionalized to realize polypeptide/metal nanoparticle hybrid materials. Theoretical approaches for the design of polypeptide assemblies will be applied and refined in an intimate collaboration with experimental studies. The chemical versatility of peptides will be harnessed to explore and exploit solution assembly processes that are hierarchical, multicomponent, thermodynamically preferred and/or kinetically controlled. Comprehensive nanoscale- through-microscale characterization of the polypeptide assembly, structural intermediates, and final materials will inform future iterations of theory and solution processing. The development of these approaches to materials assembly will facilitate the technological goal of creating robust, solution-assembly methods to produce metal nanoparticle arrays with controlled interparticle spacing and symmetry.
NON-TECHNICAL This collaborative effort parallels goals of the Materials Genome Initiative. Concepts and methods for predictive materials discovery will be developed in the context of theory-driven design of polypeptides that assemble into targeted materials and nanostructures. New experimental methods for studying and guiding molecular assembly in solution will be refined to monitor polypeptide assembly and to build polypeptide/nanoparticle materials with hierarchical complexity. The close interaction of theory and experiment is essential in the development of a predictive understanding of these materials. The concepts and methods so developed will speed the discovery of new polypeptide-based hybrid materials, and the use of the peptides to specify the arrangement and positioning of metal nanoparticles, has a variety of potential applications, including enhancement of light capture in photovoltaic cells. This collaboration will provide undergraduates, graduate students, and post-doctoral researchers at the University of Delaware and University of Pennsylvania with multidisciplinary knowledge and expertise in the design, modeling, fabrication, and characterization of peptide-based biomaterials. This physical science effort will coordinate with the Interdisciplinary Humanities Research Center at the University of Delaware. Journalism students and faculty associated with the environmental humanities program will work with the DMREF science team. This effort will produce: (1) researchers better trained in communicating science to the general public and in describing the impact of the science and any eventual technology, and (2) future journalists with experience in multidisciplinary research who are skilled in assimilating scientific nuance and complexity into discussions of the research and its impact.
