Direct evidence for antifreeze glycoprotein adsorption onto an ice surface

Aqueous solutions of antifreeze glycoproteins (AFGP) exhibit hysteresis between the freezing and melting temperatures. Several recent studies on the mechanism of function of this protein system suggest that a likely model is for the antifreeze molecules to be adsorbed onto the surface of the crystals. However, direct proof of the presence of adsorbed AFGP has eluded previous researchers. In the present study, enhanced surface second‐harmonic generation (SSHG) was observed in the presence of an active AFGP solution in contact with a pure single crystal of ice. The enhancement of SSHG is a positive indication that active AFGP molecules adsorb to the surface of ice crystals.