Freezing and Melting Hysteresis Measurements in Solutions of Hyperactive Antifreeze Protein from an Antarctic Bacteria

Abstract

Antifreeze proteins (AFPs) evolved in cold-adapted organisms and serve to protect them against freezing in cold conditions by arresting ice crystal growth. Recently, we have shown quantitatively that adsorption of AFPs not only prevents ice from growing but also from melting. This melting inhibition by AFPs, which results in superheated ice (Celik et al, PNAS 2010), is not a well-known phenomenon. Here we present our recent findings in which the Ca2+ - dependent hyperactive AFP from Marinomonas primoryensis (MpAFP) clearly displays this property. Additionally, we found that an ice crystal that is initially stabilized and protected by this type of AFP can be overgrown and then melted back to the original crystal. This repeatable process is likely due to melting inhibition, and supports the idea that AFPs bind irreversibly to ice surfaces.