Hydrophobic hydration is an important source of elasticity in elastin-based biopolymers

Molecular dynamics simulations with explicit waters have been employed to i nvestigate the dominant source of elastin's elasticity. An elastin-like pep tide, (VPGVG)(18), was pulled and released in molecular dynamics simulation s, at 10 and 42 degreesC, lasting several nanoseconds, which is consistent with the experimentally determined dielectric and NMR relaxation time scale s. At elastin's physiological temperature and degree of extension, the simu lations indicate that the orientational entropy of waters hydrating hydroph obic groups decreases during pulling of the molecule, but it increases upon release. In contrast, the main-chain fluctuations and other measures of mo bility suggest that elastin's backbone is more dynamic in the extended than released state. These results and the agreement between the simulations wi th various experimental observations suggest that hydrophobic hydration is an important source of the entropy-based elasticity of elastin. Moreover, e lastin tends to reorder itself to form a hydrophobic globule when it was he ld in its extended state, indicating that the hydrophobic effect also contr ibutes in the holding process. On the whole, our simulations support the hy drophobic mechanism of elasticity and provide a framework for description o f the molecular basis of this phenomenon.