Effect of Acidity on Chitin–Protein Interface: A Molecular Dynamics Study

Abstract

Chitin–protein interfaces exist in many biological materials such as cuticles of insects and crustaceans, which are main commercial sources of chitin fiber. In industrial processing, the extraction of chitin from these sources is achieved via acidic and alkaline treatments. As the acidity changes, the ionizable groups of protein undergo protonation/deprotonation, which may vary the mechanical properties of chitin–protein interface. In order to study the effect of acidity on this interface, we perform a series of molecular dynamics simulations and measure the adhesion strength between chitin and a short peptide sequence under both acidic and alkaline conditions, where the two termini are modified to accommodate the environment. The results indicate that the protonation state of terminus has a significant influence on the adhesion with chitin. Based on our simple model and its results, we analyze the roles of termini in the formation of hydrogen bonds and elucidate some atomistic mechanisms behind the acidity effect on chitin–protein interface, which may spotlight the engineering on biological materials with similar interfaces.