Ion-Induced Dipole Interactions and Fragmentation Times: Cα-Cβ Chromophore Bond Dissociation Channel.

The fragmentation times corresponding to the loss of the chromophore (Cα-Cβ bond dissociation channel) after photoexcitation at 263 nm have been investigated for several small peptides containing tryptophan or tyrosine. For tryptophan-containing peptides, the aromatic chromophore is lost as an ionic fragment (m/z 130), and the fragmentation time increases with the mass of the neutral fragment. In contrast, for tyrosine-containing peptides the aromatic chromophore is always lost as a neutral fragment (mass = 107 amu) and the fragmentation time is found to be fast (<20 ns).

UV Photofragmentation Dynamics of Protonated Cystine: Disulfide Bond Rupture.

Disulfide bonds (S-S) play a central role in stabilizing the native structure of proteins against denaturation. Experimentally, identification of these linkages in peptide and protein structure characterization remains challenging. UV photodissociation (UVPD) can be a valuable tool in identifying disulfide linkages.

Photofragmentation at 263 nm of small peptides containing tyrosine: the role of the charge transfer on CO.

The photofragmentation pathways at 263 nm of several small peptides containing tyrosine as the UV chromophore have been characterized using a multi-coincidence technique. A detailed study of the fragmentation dynamics of protonated Glycine-Tyrosine (GYH(+)), Tyrosine-Glycine (YGH(+)), Glycine-Tyrosine-Glycine (GYGH(+)), Alanine-Tyrosine (AYH(+)) and Tyrosine-Alanine (YAH(+)) is presented in this paper. Fragmentations occurring or initiated in an excited state are distinguished from those occurring after internal conversion to the ground electronic state by their rapid fragmentation times and binary nature.

Photofragmentation in selected tautomers of protonated adenine.

The photofragmentation by UV excitation of selectively prepared 1(+) and 3(+) tautomers of protonated adenine is studied after excitation at a 266 and 263 nm wavelengths with two different experimental set-ups located in Seoul and Orsay. While the production of 1(+) tautomers with an electrospray ion source is now well accepted, calculations were used to ascribe the preparation of 3(+) tautomers from cold adenine dimers. The fragmentation patterns are rather similar for both tautomers, suggesting similar mechanisms as a statistical fragmentation in the ground electronic state after internal conversion.