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Simulation of the Amide! Infrared Spectrum in Photoinduced Peptide Folding/Unfolding Transitions (Articolo in rivista)

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Simulation of the Amide! Infrared Spectrum in Photoinduced Peptide Folding/Unfolding Transitions (Articolo in rivista) (literal)

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Zanetti-Polzi L. [ 1,2 ] ; Aschi M. [ 1 ] ; Amadei A. [ 3 ] ; Daidone I. [ 1 ] (2013)
Simulation of the Amide! Infrared Spectrum in Photoinduced Peptide Folding/Unfolding Transitions
in The journal of physical chemistry. B; AMER CHEMICAL SOC, WASHINGTON (Stati Uniti d'America)
(literal)

Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori

Zanetti-Polzi L. [ 1,2 ] ; Aschi M. [ 1 ] ; Amadei A. [ 3 ] ; Daidone I. [ 1 ] (literal)

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[ 1 ] Univ Aquila, Dipartimento Sci Fis & Chim, I-67010 Coppito, AQ, Italy [ 2 ] CNR, Inst Nanosci, Ctr S3, I-41125 Modena, Italy [ 3 ] Univ Roma Tor Vergata, Dipartimento Sci & Tecnol Chim, I-00133 Rome, Italy (literal)

Titolo

Simulation of the Amide! Infrared Spectrum in Photoinduced Peptide Folding/Unfolding Transitions (literal)

Abstract

The amide I' infrared spectrum of a a-helical photoswitchable peptide is calculated here by means of a mixed quantum mechanics/molecular dynamics theoretical-computational methodology based on the perturbed matrix method (PMM). The contribution of specific residues to the total spectrum is also analyzed and the results compared to previous experimental spectroscopic data, obtained by means of site-specific isotope labeling at different residues, resulting in good agreement. One of the residues (Ala7) shows atypical spectroscopic behavior in both the experimental and calculated spectra, i.e., the folded-state amide I' band is shifted to higher frequencies than the unfolded-state one, while the other residues show the opposite behavior. The calculations reveal the origin of this uncommon spectroscopic trend and point to a crucial role of the molecular switch, the presence of which perturbs the conformational sampling of the peptide. Indeed, infrared spectra of the same peptide calculated in the absence of the molecular switch show that the single-residue spectrum of Ala7 does not have any distinguishing feature, resembling the spectra of the other analyzed residues. (literal)

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