Conformations of Gly(n)H+ and Ala(n)H+ peptides in the gas phase.
High-resolution ion mobility measurements and molecular dynamics simulations have been used to probe the conformations of protonated polyglycine and polyalanine (Gly(n)H and Ala(n)H+, n = 3-20) in the gas phase. The measured collision integrals for both the polyglycine and the polyalanine peptides are consistent with a self-solvated globule conformation, where the peptide chain wraps around and solvates the charge located on the terminal amine. The conformations of the small peptides are governed entirely by self-solvation, whereas the larger ones have additional backbone hydrogen bonds. Helical conformations, which are stable for neutral Alan peptides, were not observed in the experiments. Molecular dynamics simulations for Ala(n)H+ peptides suggest that the charge destabilizes the helix, although several of the low energy conformations found in the simulations for the larger Ala(n)H+ peptides have small helical regions.
Department of Chemistry, Northwestern University, Evanston, Illinois 60208 USA.
R R
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Hudgins
Y
Y
Mao
M A
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Ratner
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Jarrold
D055592:Biophysical Phenomena; D001703:Biophysics; D005740:Gases; D006860:Hydrogen Bonding; D013058:Mass Spectrometry / Q000295:instrumentation; D008958:Models, Molecular; D010455:Peptides / Q000737:chemistry*; D011487:Protein Conformation; D017433:Protein Structure, Secondary; D011522:Protons; D012996:Solutions; D013816:Thermodynamics
D005740:Gases; D010455:Peptides; D011522:Protons; D012996:Solutions; C019529:polyalanine; C011080:polyglycine