Size and Aggregation of Ice-binding Proteins Control Their Ice Nucleation Efficiency*

Ice-binding proteins are the common name shared by antifreeze proteins (AFPs) and ice nucleating proteins (INPs). It has been proposed that the size of ice-binding surface determines the function of these proteins, as INPs or AFPs. Aggregation of proteins can create large ice-binding surfaces, stabilize larger ice nucleus and enhance ice nucleation, However, the quantitative dependence of ice nucleation ability on the size and aggregation of the ice-binding surfaces has not yet been elucidated. We use molecular dynamic simulations to show that the ice nucleating ability of a ice-binding protein increases with their length and saturates at an ice freezing temperature lower that that induced by INP aggregates, because the short dimension of small ice-binding surface limits the formation of ice nucleus. We further demonstrate that INPs dimer with specific separation distance enhances the ice nucleating ability of INPs. We conclude that the size and aggregation of ice-binding proteins control their efficiencies.