Antifreeze proteins (AFPs) and glycoproteins (AFGPs) have been found in a variety of organisms that are exposed to seasonally low temperatures. These proteins lower the freezing point without significantly affecting the equilibrium melting point, thereby earning the alternative designation, thermal hysteresis (TH) proteins. Generally, it is suggested that the inhibition activities of AF(G)Ps come from their ability to adsorb specifically to some faces of ice crystal embryos. Because of their novel TH properties as well as their ability to prevent ice recrystallization, applications of AF(G)Ps for cryopreservation in the health and food industries have been explored. Recently, we have reported that the AFPs can also inhibit the formation of clathrate hydrate, an ice-like inclusion compound usually composed of natural gas components and water; this inhibition activity offers another avenue for potential applications. Remarkably, AFPs from fish and insect also showed the ability to eliminate the "memory effect", i.e. the faster reformation of clathrate hydrate after melting. Despite these observations, the interaction mechanism(s) of AF(G)Ps on ice or gas hydrate formation is not well understood.
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