Antifreeze protein NMR sensor to detect water molecular reorientation in the surface of ice

The century-old puzzle of the existence of a quasiliquid layer in the surface of ice was revisited using ice-surface binding type I antifreeze proteins with specific side chain C₁₃ labeled methyl groups. Variable temperature dependent C₁₃ spin lattice relaxation NMR experiments were carried out below 0 °C to probe the water molecular reorientations surrounding the methyl groups. The result shows that water molecular reorientations in ice surface are much more dynamic than those in bulk ice. This study demonstrates that antifreeze proteins can be used as a sensor to detect the dynamics of water in the surface of ice.