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Issue 33, 2007
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A matrix isolation study on Ac-Gly–NHMe and Ac-L-Ala–NHMe, the simplest chiral and achiral building blocks of peptides and proteins

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Abstract

The infrared absorption (IR) spectra of acetyl-N-methyl-glycine and acetyl-N-methyl-alanine have been recorded in dichloromethane and dimethyl sulfoxide-d6 solution, as well as in Ar and Kr matrices. The spectra were assigned with the help of quantum chemical calculations. Based on the assignments of the matrix-isolation IR spectra, in line with theoretical predictions, two different hydrogen bonded conformers were identified, furthermore a third conformer is likely to be present, which cannot be unambiguously identified. In dichloromethane two conformers could be observed, while in dimethyl sulfoxide a single conformer could be identified. Vibrational circular dichroism (VCD) spectra of acetyl-N-methyl-L-alanine have also been recorded in solutions and matrices. These matrix-isolation VCD spectra not only support the assignments of the matrix-isolation IR spectra, but also demonstrate that these spectra can be interpreted much easier with the help of quantum chemical calculations than the VCD spectra recorded in solutions. It is also shown that the rotatory strength of some vibrational transitions changes rapidly as a function of the backbone torsional coordinates; hence the appearance of some regions in the VCD spectra is extremely dependent on any perturbations, e.g. weak intermolecular interactions.

Graphical abstract: A matrix isolation study on Ac-Gly–NHMe and Ac-l-Ala–NHMe, the simplest chiral and achiral building blocks of peptides and proteins

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Publication details

The article was received on 04 Apr 2007, accepted on 13 Jun 2007 and first published on 14 Aug 2007


Article type: Paper
DOI: 10.1039/B705098D
Citation: Phys. Chem. Chem. Phys., 2007,9, 4698-4708
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    A matrix isolation study on Ac-Gly–NHMe and Ac-L-Ala–NHMe, the simplest chiral and achiral building blocks of peptides and proteins

    G. Pohl, A. Perczel, E. Vass, G. Magyarfalvi and G. Tarczay, Phys. Chem. Chem. Phys., 2007, 9, 4698
    DOI: 10.1039/B705098D

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