Antifreeze Mechanism Study of Ice Growth Inhibition by Spin Labeled Ice Binding Proteins

Abstract

Ice binding proteins (IBPs) were found to play critical role for various organisms to survive in extreme cold climates. We carried out the study on spin labeled type 1 IBPs whose sequence is from that of the Pseudopleuronectes americanus (winter flounder). The spin labeled sites involved in our study have undergone a manipulation on different directions along the α-helical structure. Site directed spin labeling technique was used to make the spin labeled peptides. Combination of the EPR spectra at low temperatures and observation of their inhibition to the growth of ice crystals gives us insight into their antifreeze mechanism on both molecular scale and microscopic scale. This poster will focus on presenting the experimental result of ice crystal inhibition, while another poster of my fellow student researchers will focus on the EPR result. Osmometer-microscopy technique was used to observe the ice crystals. The changes in antifreeze activities, kinetics of ice crystals’ growths and shapes of the ice crystals by these spin labeled IBPs compared with the wild type IBP were observed and will be discussed in this poster. Results include observations of IBP binding on both sides of the basal plane and prism faces of ice seed crystals. Significant differences between thermal hysteresis and crystal structured due to the binding of the Spin labeled IBPs were observed which is correlated to the EPR spectra at molecular level. Single cystal growth on the horizontal axis is observed within the hysteresis gap of the spin labeled IBPs while the wild type IBP showed no crystal growth during the hysteresis gap. There were various differences between thermal hysteresis values between the different spin labeled IBPs.