Photo-stability of peptide-bond aggregates: N-methylformamide dimers

R. Crespo-Otero, A. Mardykov, E. Sanchez-Garcia, W. Sander, M. Barbatti

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Abstract

The formation of weakly-bound dimers of N-methylformamide (NMF) and the photochemistry of these dimers after irradiation at 248 nm were explored using matrix-isolation spectroscopy. Calculations were used to characterize the diverse isomers and assign their IR spectra; non-adiabatic dynamics was simulated to understand their photo-deactivation mechanism. The most stable dimers, tt-1 and tt-2, were obtained by trans-trans aggregation (N-H⋯O-C interactions) and could be identified in the matrix. The main products formed after irradiation are the trans-cis dimers (tc-3 and tc-4), also stabilized by N-H⋯O-C interactions. In contrast to the photochemistry of the monomers, no dissociative products were observed after 248 nm irradiation of the dimers. The absence of dissociative products can be explained by a proton-transfer mechanism in the excited state that is faster than the photo-dissociative mechanism. The fact that hydrogen bonding has such a significant effect on the photochemical stability of NMF has important implications to understand the stability of peptide-bonded systems to UV irradiation.

Original languageEnglish
Pages (from-to)18877-18887
Number of pages11
JournalPhysical Chemistry Chemical Physics
Volume16
Issue number35
Early online date28 Jul 2014
DOIs
Publication statusPublished - 21 Sep 2014

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    Crespo-Otero, R., Mardykov, A., Sanchez-Garcia, E., Sander, W., & Barbatti, M. (2014). Photo-stability of peptide-bond aggregates: N-methylformamide dimers. Physical Chemistry Chemical Physics , 16(35), 18877-18887. https://doi.org/10.1039/c4cp02518k