The role of dipalmitoylphosphatidylcholine on antifreeze activity of antifreeze proteins

Abstract

In this thesis, we employ a newly developed micro-sized ice nucleation method, i.e,so-called double oil layer micro-sized crystallization technique, to examine the ice nucleation in a micro-sized water droplet with different additives. Using this "micro-sized ice nucleation method" and based on the heterogeneous nucleation theory, the inhibition effect of disaturated phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) on ice crystallization were examined quantitatively. It was found that DPPC can inhibit the ice nucleation process by adsorbing onto both the surfaces of the ice nuclei and the dust particles. The inhibition effect of AFP I and AFP III molecules on ice nucleation has been reported in recent experimental studies. We have observed the similar phenomena. However, if DPPC is added the AFP I/III solution, DPPC molecule will decrease the antifreeze activity of AFP I/III at relatively high/low supercools. These effects of DPPC on the antifreeze activity of AFP I/III is caused by DPPC molecule as a template enhances the structural match between AFP molecule and the nucleating ice.