Direct measurement of the correlated dynamics of the protein-backbone and proximal waters of hydration in mechanically strained elastin

TL;DR

This study directly measures how the dynamics of protein backbones and nearby waters in elastin change under strain, revealing an entropic mechanism behind elastin's elasticity supported by experimental and simulation data.

Contribution

It provides the first direct measurement of correlation times of protein backbones and proximal waters in strained elastin, linking molecular dynamics to elastic behavior.

Findings

Correlation times decrease with increased strain.

Proximal waters of hydration become more dynamic under strain.

Results support an entropic elasticity model for elastin.

Abstract

We report on the direct measurement of the correlation times of the protein backbone carbons and proximal waters of hydration in mechanically strained elastin by nuclear magnetic resonance methods. The experimental data indicate a decrease in the correlation times of the carbonyl carbons as the strain on the biopolymer is increased. These observations are in good agreement with short 4ns molecular dynamics simulations of (VPGVG)3, a well studied mimetic peptide of elastin. The experimental results also indicate a reduction in the correlation time of proximal waters of hydration with increasing strain applied to the elastomer. A simple model is suggested that correlates the increase in the motion of proximal waters of hydration to the increase in frequency of libration of the protein backbone that develops with increasing strain. Together, the reduction in the protein entropy accompanied with the increase in entropy of the proximal waters of hydration with increasing strain, support the notion that the source of elasticity is driven by an entropic mechanism arising from the change in entropy of the protein backbone.