Elucidating the role of water in collagen self-assembly by isotopically modulating collagen hydration

Abstract

Water is known to play an important role in collagen self-assembly, but it is still largely unclear how water–collagen interactions influence the assembly process and determine the fibril network properties. Here, we use the H 2 O/D 2 O isotope effect on the hydrogen-bond strength in water to investigate the role of hydration in collagen self-assembly. We dissolve collagen in H 2 O and D 2 O and compare the growth kinetics and the structure of the collagen assemblies formed in these water isotopomers. Surprisingly, collagen assembly occurs ten times faster in D 2 O than in H 2 O, and collagen in D 2 O self-assembles into much thinner fibrils, that form a more inhomogeneous and softer network, with a fourfold reduction in elastic modulus when compared to H 2 O. Combining spectroscopic measurements with atomistic simulations, we show that collagen in D 2 O is less hydrated than in H 2 O. This partial dehydration lowers the enthalpic penalty for water removal and reorganization at the collagen–water interface, increasing the self-assembly rate and the number of nucleation centers, leading to thinner fibrils and a softer network. Coarse-grained simulations show that the acceleration in the initial nucleation rate can be reproduced by the enhancement of electrostatic interactions. These results show that water acts as a mediator between collagen monomers, by modulating their interactions so as to optimize the assembly process and, thus, the final network properties. We believe that isotopically modulating the hydration of proteins can be a valuable method to investigate the role of water in protein structural dynamics and protein self-assembly.

Bioarchitectural Design of Bioactive Biopolymers: Structure–Function Paradigm for Diabetic Wound Healing

“…Its tertiary structure comprises three polypeptide chains (mainly composed of amino acids like proline, hydroxyproline, and glycine) wrapped in a left-handed triple helix to form collagen fibrils [190]. The process of collagen fibrillogenesis is strongly driven by increased entropy, resulting in a greater level of disorder at the water-protein interface [191]. Fibroblasts synthesize collagen de novo an integral part of normal wound healing process [192].…”