Abstract by Steven Draper
Chemistry and Biochemistry
Polyethylene Glycol and the Hydrophobic Effect
The hydrophobic effect (the exclusion of water in the folding of proteins, resulting in the burial of hydrophobic residues) contributed greatly to the protein folding process. Exposed hydrophobic patches can cause an otherwise effective therapeutic to aggregate and become inactive. The conjugation of polyethylene glycol (PEGylation) has been shown to be able to desolvate the residues around it. We have created an exposed hydrophobic patch in the WW domain by inserting leucine at positions 12 and 14 and inserted propargyloxy phenylalanine (PrF) at position 23, which is near both position 12 and 14. We PEGylated with a PEG azide using CLICK chemistry. We found that PEGylation at this site increased the stability of the peptide by -0.57 ± 0.03 kcal/mol. Next, we tried changing the solvent excluded volume of the residues by putting phenylalanine and cyclohexyl alanine in positions 12 and 14. Phenylalanyl was stabilized by -0.33 ± 0.02 kcal/mol and cyclohexyl alanine was stabilized by -1.00 ± 0.03 kcal/mol. Interestingly, cyclohexyl alanine had a large negative change in heat capacity, which implies the burial of hydrophobic surface area.