Stereochemical Sequence Ion Selectivity: Proline versus Pipecolic-acid-containing Protonated Peptides
| Autor: | Shanshan Guan, Maha T. Abutokaikah, Benjamin J. Bythell |
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| Rok vydání: | 2016 |
| Předmět: |
Models
Molecular Steric effects Proline Collision-induced dissociation Stereochemistry 010401 analytical chemistry Stereoisomerism Protonation 010402 general chemistry 01 natural sciences Affinities Mass Spectrometry 0104 chemical sciences chemistry.chemical_compound chemistry Fragmentation (mass spectrometry) Structural Biology Pipecolic Acids Quantum Theory Peptide bond Protons Peptides Spectroscopy Pipecolic acid |
| Zdroj: | Journal of the American Society for Mass Spectrometry. 28:182-189 |
| ISSN: | 1044-0305 |
| Popis: | Substitution of proline by pipecolic acid, the six-membered ring congener of proline, results in vastly different tandem mass spectra. The well-known proline effect is eliminated and amide bond cleavage C-terminal to pipecolic acid dominates instead. Why do these two ostensibly similar residues produce dramatically differing spectra? Recent evidence indicates that the proton affinities of these residues are similar, so are unlikely to explain the result [Raulfs et al., J. Am. Soc. Mass Spectrom. 25, 1705-1715 (2014)]. An additional hypothesis based on increased flexibility was also advocated. Here, we provide a computational investigation of the "pipecolic acid effect," to test this and other hypotheses to determine if theory can shed additional light on this fascinating result. Our calculations provide evidence for both the increased flexibility of pipecolic-acid-containing peptides, and structural changes in the transition structures necessary to produce the sequence ions. The most striking computational finding is inversion of the stereochemistry of the transition structures leading to "proline effect"-type amide bond fragmentation between the proline/pipecolic acid-congeners: R (proline) to S (pipecolic acid). Additionally, our calculations predict substantial stabilization of the amide bond cleavage barriers for the pipecolic acid congeners by reduction in deleterious steric interactions and provide evidence for the importance of experimental energy regime in rationalizing the spectra. Graphical Abstract ᅟ. |
| Databáze: | OpenAIRE |
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