Thermal hysteresis of antifreeze proteins considering Fragilariopsis cylindrus

Abstract

The diatom species Fragilariopsis cylindrus produces antifreeze proteins (AFPs) of moderate thermal hysteresis. Two concepts are often used in order to describe a thermal hysteresis, on the one hand the irreversible nucleation growth described by the Gibbs-Thomson relation and on the other hand a nonlinear adsorption kinetics of the ice-binding proteins. We refer to the Landau's phase transition theory and predict a saturation concentration of AFPs for the maximal freezing depression. The derived functional relation between temperature and AFP concentration is more complex than a simple power law as suggested by thermal hysteresis experiments. With the parameter set obtained for Fragilariopsis cylindrus the modelled curve is comparable with the often used square root law.