Effect of unfolding on the thickness of the hydration layer of a protein

Properties of water in the hydration layer around a protein is intimately correlated with its function. A knowledge of the thickness of the hydration layer is important to understand its role in guiding the folding-unfolding of the protein. We have performed atomistic molecular dynamics simulations of the folded native and a partially unfolded molten globule structure of the villin headpiece subdomain or HP-36 in aqueous solution to estimate the effect of unfolding on the thickness of hydration layer around different segments of the protein. In particular, several dynamic properties of water around different segments of the folded native and the unfolded structure have been calculated by varying the thickness of the hydration layers. It is found that unfolding of a segment of the protein is correlated with the dynamics of water around it, i.e., within the first hydration layer. The effect of unfolding on water properties has been found to diminish when water molecules present beyond the first hydration layer were included in the calculations.