Perturbation of Hydrogen Bonding Network Plays an Important Role in Determining Antifreeze Activity

Abstract

In order to develop new antifreeze agents, it is crucial to understand the antifreeze activity. The adsorption-inhibition mechanism has been widely accepted, and most previous studies focus on ice-binding affinity of additive molecules but rarely discuss their influence on the hydrogen bonding network of ice. Herein, we investigate the ice recrystallization inhibition (IRI) activity of two structurally similar molecules, histidine (His) and phenylalanine (Phe). It is verified by experiment that Phe has excellent IRI activity, while His does not. Molecular dynamics simulation is conducted to study the process of ice growth with amino acids and to explore the origin of the difference between His and Phe. We find that His is prone to be swallowed up by ice and thus no longer hinders its growth, whereas Phe can remain unswallowed on the ice surface for a long period, which is attributed to their different abilities to perturb the hydrogen bonding network. Based on a statistical analysis of oxygen–hydrogen bond orientations, we propose a method to evaluate the order of the hydrogen bonding network. With this method, the IRI activity of His and Phe can be well interpreted, and the influence of different groups on the hydrogen bonding network can be quantified. This study takes the structural integrity of ice into consideration and provides a possibility to investigate the influence of different additive molecules on hydrogen bonding network, which is expected to improve the understanding of antifreeze mechanism.