Simplicity is crucial to design optimization at...( MIT researchers who study the struct...)

MIT researchers who study the structure of protein-based materials with the aim of learning the key to their lightweight and robust strength have discovered that the particular arrangement of proteins that produces the sturdiest product is not the arrangement with the most built-in redundancy or the most complicated pattern. Instead, the optimal arrangement of proteins in the rope-like structures they studied is a repeated pattern of two stacks of four bundled alpha-helical proteins.

This composition of two repeated hierarchies (stacks and bundles) provides great strengththe ability to withstand mechanical pressure without giving wayand great robustnessthe ability to perform mechanically, even if flawed. Because the alpha-helical protein serves as the building block of many common materials, understanding the properties of those materials has been the subject of intense scientific inquiry since the protein's discovery in the 1940s.

In a paper published in the Jan. 27 online issue of Nanotechnology, Markus Buehler and Theodor Ackbarow describe a model of the protein's performance, based on molecular dynamics simulations. With their model they tested the strength and robustness of four different combinations of eight alpha-helical proteins: a single stack of eight proteins, two stacks of four bundled proteins, four stacks of two bundled proteins, and double stacks of two bundled proteins. Their molecular models replicate realistic molecular behavior, including hydrogen bond formation in the coiled spring-like alpha-helical proteins.

"The traditional way of designing materials is to consider properties at the macro level, but a more efficient way of materials' design is to play with the structural makeup at the nanoscale," said Buehler, the Esther and Harold E. Assistant Professor in the Department of Civil and Environmental Engineering. "This provides a new paradigm in engineering that enables us to design a new class of m
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