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Issue 31, 2011
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Temperature-dependent intensity anomalies in amino acid esters: weak hydrogen bonds in protected glycine, alanine and valine

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Abstract

Esters of glycine, alanine and valine are investigated by FTIR and Raman spectroscopy in supersonic jets as gas phase model systems for the neutral peptide N-terminus. The NH-stretching vibrations exhibit very large temperature- and substitution-dependent intensity anomalies which are related to weak, bifurcated intramolecular hydrogen bonds to the carbonyl group. Comparison to theory is only satisfactory at low temperature. Spectral NH aggregation shifts are small or even negligible and the associated IR intensity is remarkably low. In the case of valine, chirality recognition effects are nevertheless detected and rationalized. Comparison to quantum-chemical calculations for dimers shows that dispersion interactions are essential. It also rules out cooperative hydrogen bond topologies and points at deficiencies in standard harmonic treatments with the linear dipole approximation.

Graphical abstract: Temperature-dependent intensity anomalies in amino acid esters: weak hydrogen bonds in protected glycine, alanine and valine

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The article was received on 23 Mar 2011, accepted on 08 Jun 2011 and first published on 28 Jun 2011


Article type: Paper
DOI: 10.1039/C1CP20883G
Citation: Phys. Chem. Chem. Phys., 2011,13, 14119-14130

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    Temperature-dependent intensity anomalies in amino acid esters: weak hydrogen bonds in protected glycine, alanine and valine

    K. E. Otto, S. Hesse, T. N. Wassermann, C. A. Rice, M. A. Suhm, T. Stafforst and U. Diederichsen, Phys. Chem. Chem. Phys., 2011, 13, 14119
    DOI: 10.1039/C1CP20883G

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