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for Turning weakness into strength: How protein materials balance strength, robustness and adaptability
==Markus J. Beuhler, Ph.D.==

===Turning weakness into strength: How protein materials balance strength, robustness and adaptability===

Biology exquisitely creates hierarchical structures, where initiated at nano scales, are exhibited in macro or physiological multifunctional materials to provide structural support, force generation, catalytic properties or energy conversion. This is exemplified in a wide range of biological materials such as hair, skin, bone, spider silk or cells, which play important roles in providing key functions to biological systems. This talk focuses on multiscale studies of deformation and failure of biological protein materials, used here to elucidate fundamental design concepts in order to understand physiological functions, disease mechanisms as well as to translate new material paradigms towards engineered materials. Based on a multiscale simulation approach validated through multiscale experiments, we explicitly consider the architecture of proteins across multiple scales, including the details of chemical bonding and explain how complex multifunctional properties of protein materials emerge. I will present a survey of recent studies of major classes of protein materials, including cellular protein networks, beta-sheet structures as found in spider silk and Alzheimer’s disease, as well as collagenous tissues that form the structure of tendon and bone. Case studies will be presented that illustrate size effects in protein materials, flaw-tolerance mechanisms, and applications of materials science to genetic diseases, showing how structural defects at the molecular level can have profound effects at the material behavior at larger scales. Our work explains a universal materials design paradigm found in biology, where the formation of hierarchical structures at multiple scales is used to overcome the intrinsic limitations of inferior building blocks such as weak H-bonds. We show that through this paradigm, it is possible to create highly functional, tunable and changeable materials out of simple, abundant and inexpensive constituents. Analogies with engineered materials such as polymers and metals in different geometries will be discussed, and new approaches towards the design of adaptable, mutable and active nanomaterials will be presented. 

[1]	S. Keten, Z. Xu, B. Ihle, M.J. Buehler, “Nanoconfinement controls stiffness, strength and mechanical toughness of -sheet crystals in silk”, Nature Materials, 10.1038/nmat2704, 2010
[2]	M.J. Buehler, “Strength in numbers”, Nature Nanotechnology, Vol. 5(3), pp. 172-174, 2010
[3]	Gautieri, S. Uzel, S. Vesentini, A. Redaelli, M.J. Buehler, “Molecular and mesoscale disease mechanisms of Osteogenesis Imperfecta”, Biophysical J., Vol. 97(3), pp. 857-865, 2009
[4]	M.J. Buehler, Y. Yung, “Deformation and failure of protein materials in extreme conditions and disease”, Nature Materials, Vol. 8(3), pp. 175-188, 2009
[5]	Z. Qin, L. Kreplak, M.J. Buehler, “Hierarchical structure controls nanomechanical properties of vimentin intermediate filaments”, PLoS ONE, Vol. 4(10), paper # e7294, 2009

 
Brief biography – Markus Buehler

Markus Buehler is the Esther and Harold E. Edgerton Associate Professor in the Department of Civil and Environmental Engineering at the Massachusetts Institute of Technology. Before joining MIT in 2005, he served as the Director of Multiscale Modeling and Software Integration at Caltech’s Materials and Process Simulation Center. He received a Ph.D. in chemistry from the Max Planck Institute for Metals Research in Stuttgart after obtaining a M.S. in Engineering Mechanics from Michigan Tech, and undergraduate studies in Chemical Engineering at the University of Stuttgart. Professor Buehler’s research focuses on bottom-up simulation of structural and mechanical properties of biological, bioinspired and synthetic materials across multiple scales, with a specific focus on materials failure from a nanoscale and molecular perspective.  His recent work has focused on applying a computational materials science approach to study materials failure in biological systems, including the investigation of material breakdown in diseases.  Professor Buehler has published more than 110 articles on computational modeling of materials using various types of simulation techniques. He was cited as one of the top engineers in the United States between the ages of 30-45 through invitation to the 2007 National Academy of Engineering-Frontiers in Engineering symposium of the National Academy of Engineering. Professor Buehler has also received the 2007 National Science Foundation CAREER award, the 2008 U.S. Air Force Young Investigator Award, the 2008 Navy Young Investigator Award, and the 2008 DARPA Young Faculty Award. In 2009, his work was recognized by the Presidential Early Career Award for Scientists and Engineers, PECASE.  He serves as a member of the editorial board of several international journals including: PLoS ONE, International Journal of Applied Mechanics, Acta Mechanica Sinica, Mechanical Behavior of Biomedical Materials, and Journal of Computational and Theoretical Nanoscience.
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