EXPLAINING THE PUZZLING BEHAVIOR
Buehler and undergraduate student Xuefeng Chen, graduate student Sinan Keten, and Theodor Ackbarow, a graduate student from the University of Stuttgart working in Buehlers lab at MIT, set up a six-month computer simulation study. They worked with two different types of common proteins: vimentinan alpha-helical filament protein that plays an important role in cellular signaling and stabilityand amyloidal fibrilsbeta-folded proteins. These protein motifs form the basis of many natural materials, such as hair, hoof, wool, spider silk, and the prions that build up in the brains of Alzheimers patients.
Hydrogen bonds are the basic chemical bonds that hold together proteins, similar to trusses and beams in buildings, and play a key role in controlling the behavior of these structures.
The researchers placed strain on the proteins by pulling on the ends, trying different pressures applied at different rates. They found that the hydrogen bonds in both the alpha-helical-type vimentin proteins and the beta-fibril-type amyloids behaved similarly. At higher rates, hydrogen bonds begun to break apart one at a time, earlier in the process. But when the pressure is applied more slowly, the bonds hold out longer, but break three at a time when they go.
The slow deformation rate in proteins is most relevant in normal biological function, but the fast rate could be important during tissue injuries such as the shock impact in accidents and during formation of fractures in biological tissues, said Buehler.
This work adds an important
|Contact: Denise Brehm|
Massachusetts Institute of Technology, Department of Civil and Environmental Engineering