<p>Since some antifreeze proteins and glycoproteins
(AF(G)Ps) cannot directly bind to all crystal planes, they change ice crystal morphology
by minimizing the area of the crystal planes to which they cannot bind until crystal
growth is halted. Previous studies found that growth along the <i>c</i>-axis
(perpendicular to the basal plane, the crystal plane to which these AF(G)Ps
cannot bind) is accelerated by some AF(G)Ps, while growth of other planes is
inhibited. The effects of this growth acceleration on crystal morphology and on
the thermal hysteresis activity are unknown to date. Understanding these
effects will elucidate the mechanism of ice growth inhibition by AF(G)Ps. Using
cold stages and an Infrared laser, ice growth velocities and crystal
morphologies in AF(G)P solutions were measured. Three types of effects on
growth velocity were found: concentration-dependent acceleration,
concentration-independent acceleration, and concentration-dependent
deceleration. Quantitative crystal morphology measurements in AF(G)P solutions
demonstrated that adsorption rate of the proteins to ice plays a major role in
determining the morphology of the bipyramidal crystal. These results demonstrate
that faster adsorption rates generate bipyramidal crystals with diminished
basal surfaces at higher temperatures compared to slower adsorption rates. The
acceleration of growth along the <i>c</i>-axis generates crystals with smaller
basal surfaces at higher temperatures leading to increased growth inhibition of
the entire crystal.<a></a></p>
Ice Growth Acceleration by Antifreeze Proteins Leads to Higher Thermal Hysteresis Activity
