Date of Award

Fall 2018

Project Type

Dissertation

Program or Major

Biochemistry

Degree Name

Doctor of Philosophy

First Advisor

Krisztina Varga

Second Advisor

Richard H Cote

Third Advisor

Feixia Chu

Abstract

Antifreeze proteins (AFPs) are a unique class of protein characterized by their ability to depress the freezing point of water sufficient to prevent the formation of ice crystals by adsorbing to the surface of ice crystals. This unique ability allows organisms (e.g. plants, fish, insects, etc.) which live in extremely cold climates to survive. Because of these proteins’ ability to prevent and slow the rate of ice crystal formation, they have great potential in the application of cryopreservation in medicine, agriculture and food science. Antifreeze proteins have been known for over five decades, however, their exact mechanism of action is still under investigation. In this study, we have characterized the antifreeze protein ApAFP752 from the beetle Anatolica polita to better understand method of action of antifreeze activity of insect antifreeze proteins and to identify it potential applications in cryoprotection. We found the protein to have a β-helix secondary structure, similar to other known insect antifreeze proteins. Additionally, the protein was found to confer some cryoprotection to cellular systems.

We have also investigated the effects of ionic liquids on protein biophysics. Ionic liquids are highly viscous liquids at room temperature comprised entirely of ions, which makes it challenging to study their interactions with protein by traditional NMR methods. It has been proposed that ILs can be tuned to alter the structural and biophysical properties of biomacromolecules. In this study, the effect of an ionic liquid (1-butyl-3-methylimidazolium bromide, [C4-mim]Br) on the structure and dynamics of the model protein GB1 was investigated using high-resolution magic angle spinning (HR-MAS) NMR spectroscopy. HR-MAS NMR proved to be a viable tool for the elucidation of the molecular mechanism of ionic liquid – protein interactions.

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