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Issue 10, 2004
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Photo-induced dissociation of protonated tryptophan TrpH+: A direct dissociation channel in the excited states controls the hydrogen atom loss

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Abstract

Protonated tryptophan ions (TrpH+) are generated by electrospray ionization and dissociated by irradiation with a UV laser. Different photo-fragments are observed among which a new photo-induced dissociation channel leading to the loss of a hydrogen atom that is not observed in conventional collision-induced dissociation. A tryptophan radical cation (Trp+) is produced in this process that subsequently leads to the m/z = 130 fragment through a Cα–Cβ bond cleavage, a typical fragmentation product of the Trp+ radical cation generated either by electron impact or by photo-ionization. These results can be understood considering the excited states of protonated tryptophan: UV excitation of TrpH+ produces a mixed ππ*/πσ* state, the ππ* state being mainly located on the indole chromophore while the πσ* is mainly on the protonated terminal amino group. This πσ* state is repulsive along the N–H bond coordinate and leads either to hydrogen atom detachment producing a Trp+ radical cation that undergoes further fragmentations or to internal conversion to the ground state of the protonated TrpH+ ion.

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Publication details

The article was received on 04 Dec 2003, accepted on 03 Mar 2004 and first published on 27 Apr 2004


Article type: Paper
DOI: 10.1039/B315425D
Citation: Phys. Chem. Chem. Phys., 2004,6, 2628-2632

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    Photo-induced dissociation of protonated tryptophan TrpH+: A direct dissociation channel in the excited states controls the hydrogen atom loss

    H. Kang, C. Dedonder-Lardeux, C. Jouvet, S. Martrenchard, G. Grégoire, C. Desfrançois, J.-P. Schermann, M. Barat and J. A. Fayeton, Phys. Chem. Chem. Phys., 2004, 6, 2628
    DOI: 10.1039/B315425D

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