Digitized Honors Theses (2002-2017)

Date of Award

5-2010

Document Type

Undergraduate Thesis

Degree Name

BS

Department

Chemistry

Faculty Mentor

Andrzej Wierzbicki, Ph.D.

Advisor(s)

Scott Miller, Ph.D., Alan Salter, Ph.D.

Abstract

Antifreeze proteins are a special class of peptides that inhibit the growth of ice crystals by binding to their surfaces and preventing further addition of water molecules. The most interesting aspect of these peptides is the fact that they often contain mostly hydrophobic residues, yet are still soluble and furthermore, bind to ice crystal. Past studies have shown that both hydrophobic and hydrophilic residues play a role in the antifreeze peptide binding mechanism, but the hydrophobic residues play a more significant role than originally believed. A subsequent computational study showed that methane binds to ice crystal surfaces, providing indirect evidence that methyl groups of amino-acid side chains may favorably interact with ice surfaces. Furthermore, methane preferentially binds to the (201) and (2-10) planes, which are the accepted winter flounder and shorthorn sculpin binding planes. Given these findings, this study set out to test the importance of certain hydrophobic residues contained in the shorthorn sculpin antifreeze protein with regard to its ability to bind ice. Three mutated versions of the shorthorn sculpin peptide were synthesized, and their ice binding abilities were tested using a nanoliter osmometer. It was found that the steric considerations and electrostatic charges of the residues located near the ice-binding side of the helix are very important; i.e., placing sterically bulky or charged residues too close to this area inhibits the peptides ability to restrict ice growth. In addition, it was found that the charged residues present in the short sequence before the praline residue (P6) are critical for the peptide's solubility.

Comments

© 2010 R. Wesley Edmunds ALL RIGHTS RESERVED

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