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Volume 177, 2015
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Vibronic structure in the far-UV electronic circular dichroism spectra of proteins

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Abstract

The Franck–Condon effect is considered and the vibrational structure of the πnbπ* transition of the peptide backbone is incorporated into matrix method calculations of the electronic circular dichroism (CD) spectra of proteins in the far-ultraviolet. We employ the state-averaged CASPT2 method to calculate the ground and πnbπ* excited state geometries and frequencies of N-methylacetamide (NMA), which represents the peptide chromophore. The results of these calculations are used to incorporate vibronic levels of the excited states into the matrix method calculation. The CD spectra of a set of 49 proteins, comprising a range of structural types, are calculated to assess the influence of the vibrational structure. The calculated spectra of α-helical proteins are better resolved using the vibronic parameters and correlation between the experimental and the calculated intensity of less regular β structure proteins improves over most wavelengths in the far-UV. No obvious improvement is observed in the calculated spectra of regular β-sheet proteins. Our high-level ab initio calculations of the vibronic structure of the πnbπ* transition in NMA have provided some further insight into the physical origins of the nature of protein CD spectra in the far-UV.

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Publication details

The article was received on 29 Aug 2014, accepted on 05 Nov 2014 and first published on 21 Jan 2015


Article type: Paper
DOI: 10.1039/C4FD00163J
Author version available: Download Author version (PDF)
Citation: Faraday Discuss., 2015,177, 329-344
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    Vibronic structure in the far-UV electronic circular dichroism spectra of proteins

    Z. Li, D. Robinson and J. D. Hirst, Faraday Discuss., 2015, 177, 329
    DOI: 10.1039/C4FD00163J

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