molecular insight into the adsorption/inhibition of type i and iii antifreeze protein to hydrate surface: molecular dynamics simulation study

Antifreeze proteins (afp) impede freezing of bodily fluids in many organisms at subzero temperatures. recently, some afps have been found to inhibit gas hydrates formation, and their detailed mechanism remains elusive. using in silico molecular dynamics, we studied the mechanism of two families of afp (type i and iii) on methane hydrate inhibition. moreover, the effect of site-directed mutagenesis on afp iii (n14s/t18n/q44t) was investigated to elucidating the role of hydrogen bond in antifreeze activity. structural and dynamical aspects of protein residues and water molecules at the hydrate interface propose that type iii afp operates by the adsorption-inhibition mechanism on hydrate as well as type i afp. entrapment of pendant groups of some protein residues in the empty half-cages lead to binding of afp on the hydrate interface. hydrophobic interaction along with hydrogen bonds between pendant groups and nearby water molecules contribute in the binding of afp at the hydrate surface. formation of curvature on the water/hydrate interface changes the pattern of hydrate growth and consequently cause inhibition. moreover, the different arrangements of water molecules on the two side of protein cause entropy effect and the presence of afp lead to mass transfer resistance in hydrate growth