ANYL 81 |
| We have investigated the conformational effects on the gas-phase acidities of a series of cysteine-polyalanine peptides, Cys-(Ala)n-(NH2). We measured the acidity of the cysteine residue through collision-induced dissociation (CID) bracketing experiments and the kinetic method carried out in a triple-quadrupole mass spectrometer (Varian 1200). We found that the acidity of the cysteine residue increases systematically with the increase in the lengths of the polyalanine peptides. We modeled the conformations of the peptides through molecular dynamics simulations and we calculated the theoretical acidities using density functional theory. Molecular modeling shows that both the neutral and the deprotonated Cys-(Ala)7-10-(NH2) exist as stable helices. Our studies suggest that the helical conformation may make a significant contribution to the acidity of the peptides longer than eight amino acid residues. |
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General Papers
7:00 PM-9:00 PM, Sunday, 10 September 2006 Moscone Center -- Hall D, Poster
Division of Analytical Chemistry |