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Author: search.filters.author.Chakraborty, ShamikSubject: search.filters.subject.Peptides

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    Gas phase IR spectra of tri-peptide Z-Pro-Leu-Gly: Effect of C-terminal amide capping on secondary structure
    (Elsiever, 2012-04-02) Chakraborty, Shamik
    Three-residue peptides capped with benzyloxycarbonyl (Z-) group, Z-Pro-Leu-Gly–NH2 and Z-Pro-Leu-Gly–OH, are investigated by infrared (IR) spectroscopy, using supersonic-jet laser desorption technique, in the N–H and O–H stretching frequency ranges. The IR spectra show clear evidence of the formation of different hydrogen-bonding network in the two peptides. The possible gas phase structure is proposed from density functional theory calculations using cc-pVDZ basis set. The Z-Pro-Leu-Gly–OH in the gas phase forms successive γ-turn structure with free C-terminal carboxyl group whereas main structural element in Z-Pro-Leu-Gly–NH2 is β-turn with C-terminal single bondNH2 group forming hydrogen bond. Structural information is employed to predict their binding capability in gas phase
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    Gas-phase spectroscopy and anharmonic vibrational analysis of the 3-residue peptide Z-Pro-Leu-Gly-NH2 by the laser desorption supersonic jet technique
    (Elsiever, 2013-06-20) Chakraborty, Shamik
    The electronic excitation and infrared (IR) spectra of a capped tri-peptide, Z-PLG-NH2 (Z = benzyloxycarbonyl, P = Pro, L = Leu, G = Gly), were measured in the gas phase by using the laser desorption supersonic jet technique. By measuring an ultraviolet–ultraviolet hole burning spectrum, it was found that Z-PLG-NH2 has the maximum three conformers in the gas phase, but that the population is mainly distributed to a single conformation. Molecular dynamics simulations and density functional theory calculations well-reproduced the observed IR spectrum, except for splitting of the NH stretching bands by a β-turn structure that corresponds to a global minimum structure. Anharmonic vibrational analysis by vibrational quasi-degenerate perturbation theory (VQDPT) successfully reproduced the anharmonic splitting, and confirmed the assignments.