Jump to main content
Jump to site search
PLANNED MAINTENANCE Close the message box

Scheduled maintenance upgrade on Thursday 4th of May 2017 from 8.00am to 9.00am (BST).

During this time our websites will be offline temporarily. If you have any questions please use the feedback button on this page. We apologise for any inconvenience this might cause and thank you for your patience.


Issue 29, 2012
Previous Article Next Article

Cα–Cβ chromophore bond dissociation in protonated tyrosine-methionine, methionine-tyrosine, tryptophan-methionine, methionine-tryptophan and their sulfoxide analogs

Author affiliations

Abstract

Cα–Cβ chromophore bond dissociation in some selected methionine-containing dipeptides induced by UV photons is investigated. In methionine containing dipeptides with tryptophan as the UV chromophore, the tryptophan side chain is ejected either as an ion or as a neutral fragment while in dipeptides with tyrosine, the tyrosine side chain is lost only as a neutral fragment. Mechanisms responsible for these fragmentations are proposed based on measured branching ratios and fragmentation times, and on the results of DFT/B3-LYP calculations. It appears that the Cα–Cβ bond cleavage is a non-statistical dissociation for the peptides containing tyrosine, and occurs after internal conversion for those with tryptophan. The proposed mechanisms are governed by the ionization potential of the aromatic side chain compared to that of the rest of the molecule, and by the proton affinity of the aromatic side chain compared to that of the methionine side chain. In tyrosine-containing peptides, the presence of oxygen on sulfur of methionine presumably reduces the ionization potential of the peptide backbone, facilitating the loss of the side chain as a neutral fragment. In tryptophan-containing peptides, the presence of oxygen on methionyl-sulfur expedites the transfer of the proton from the side chain to the sulfoxide, which facilitates the loss of the neutral side chain.

Graphical abstract: Cα–Cβ chromophore bond dissociation in protonated tyrosine-methionine, methionine-tyrosine, tryptophan-methionine, methionine-tryptophan and their sulfoxide analogs

Back to tab navigation
Please wait while Download options loads

Publication details

The article was received on 11 Mar 2012, accepted on 08 May 2012 and first published on 08 May 2012


Article type: Paper
DOI: 10.1039/C2CP40773F
Citation: Phys. Chem. Chem. Phys., 2012,14, 10225-10232
  •   Request permissions

    Cα–Cβ chromophore bond dissociation in protonated tyrosine-methionine, methionine-tyrosine, tryptophan-methionine, methionine-tryptophan and their sulfoxide analogs

    S. S. Kumar, B. Lucas, S. Soorkia, M. Barat and J. A. Fayeton, Phys. Chem. Chem. Phys., 2012, 14, 10225
    DOI: 10.1039/C2CP40773F

Search articles by author