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Issue 1, 2012
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Experimental thermodynamics of free glycine conformations: the first Raman experiment after twenty years of calculations

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Abstract

Low-frequency, gas-phase vibrational (Raman) spectroscopy was used in conjunction with a jet-cooled technique and ab initio calculations to study the intrinsic thermodynamic properties of the free (gas-phase) amino acidglycine (Gly, H2NCHRCOOH). The first experimental evaluation of the enthalpy differences between the Gly conformations in the vapor phase is presented. The enthalpy values were determined to be 0.33 ± 0.05 and 1.15 ± 0.07 kcal mol−1 for the ccc and gtt rotamers, respectively; the corresponding relative entropy values were −2.86 ± 0.12 and −0.12 ± 0.16 cal mol−1 K−1, respectively. It was proven that the low-frequency Raman and infrared spectroscopy is capable of estimating intrinsic thermodynamic parameters of protein building blocks, such as intermolecular hydrogen bonds (ccc conformer) and rotation around one of the bonds (N–C, gtt conformer). The inaccuracy of the RRHO approximation to Gly conformers was experimentally confirmed. Benchmark data for quantum theory and molecular dynamics were provided.

Graphical abstract: Experimental thermodynamics of free glycine conformations: the first Raman experiment after twenty years of calculations

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Publication details

The article was received on 17 Mar 2011, accepted on 21 Jul 2011 and first published on 15 Aug 2011


Article type: Paper
DOI: 10.1039/C1CP20805E
Citation: Phys. Chem. Chem. Phys., 2012,14, 99-103
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    Experimental thermodynamics of free glycine conformations: the first Raman experiment after twenty years of calculations

    R. M. Balabin, Phys. Chem. Chem. Phys., 2012, 14, 99
    DOI: 10.1039/C1CP20805E

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