Isothermal Calorimetry Study of the Interactions of Type I Antifreeze Proteins with a Lipid Model Membrane

In this paper, we report our study of thermodynamic parameters of the interactions of antifreeze proteins (AFP) type I and it short segments with DMPC unilamellar vesicles as model for cell membrane. The heat of interactions between AFP's and the model cell membrane were studied by Isothermal Titration Calorimetry (ITC) at temperatures above and below phase transition temperatures of the membrane. It is shown that heat of interactions is linearly dependent on the temperatures below the phase transition of the membrane and constant at temperatures above phase. The heat of interaction above phase transition is assigned to the interaction of the AFP with the membrane, while below phase transition the ordering effect of the AFP influence the heat of interaction.