The effect of winter flounder antifreeze protein and its mutants on methane hydrate growth: A molecular dynamic simulation study

Abstract

Natural gas hydrates (NGH) are widely found in seafloor sediments. In engineering, it is usually necessary to inject 60% of thermodynamic inhibitors, which makes hydrate extraction costly and polluting. Currently, kinetic inhibitors have attracted much attention due to their low injection dose and environmental friendliness, but the research is costly and time-consuming. In this study, we investigated the interaction between winter flounder antifreeze proteins (AFPs) and methane hydrate growth using molecular dynamics simulations. AFPs adsorbed on the hydrate surface and hindered the mass transfer of methane molecules. At the same time, the water molecules around the AFP adsorption surface are in a quasi-liquid state, a structure that facilitates the binding of AFPs to the hydrate surface. Analysis of the probability of amino acid adsorption showed that AFP was adsorbed to the hydrate surface through a combination of hydrophobic and hydrogen bonding interactions. Subsequent directional mutagenesis experiments showed that increasing the hydrophobicity of AFP rather weakens its adsorption capacity. This suggests that excessive hydrophobicity of AFP may be counterproductive to its adsorption on the hydrate surface. These findings deepen the understanding of the AFP mechanism and its potential for the development of novel hydrate inhalants.