Date of Award

2007

Degree Type

Thesis

Department

Chemical and Biomedical Engineering

First Advisor

Holland, Nolan

Subject Headings

Antifreeze proteins, Phospholipids, Membranes (Biology) -- Thermal properties

Abstract

Heart transplantation is a successful therapeutic procedure for the patients with end stage heart disease. Various preservative techniques have been developed to increase the shelf life of organs, but still there can be tissue damage during cold storage. One mechanism leading to damage is disruption of cell plasma membranes as they pass through temperature induced phase transitions. The addition of antifreeze protein (AFP) or glycoprotein (AFGP) to storage solutions has been hypothesized to reduce the leakiness of lipid membranes. From studies using liposomes it has been shown that AFPs can prevent leakage through lipid membranes, although the mechanism of interaction is not known. We hope to elucidate the mechanism by investigating AFP-lipid interactions at the air-water interface. We measured surface pressure-area isotherms using a mini Langmuir Trough (Nima 112D) to observe the interactions between lipids and AFPs. We investigated two phospholipids with zwitterionic head groups (DPPC, DMPE) and four proteins - one Type I AFP, two Type III AFPs (RD1, RD3) and BSA control. Our results showed weak or no interactions between all protein-lipid combinations except for the combinations of RD3 with DPPC and Type I with DMPE. These interactions were observed as an increase in molecular area at high surface pressure compared to pure lipid monolayers. These results suggest that not all antifreeze proteins behave similarly with any particular type of lipid. Our future plan is to compare these isotherms with liposome leakage studies and predict which proteins are good preservation agents, so that we will be able to develop a protocol by which one will be able to determine a priori whether a compound will be a successful membrane protector

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