Ultrafast deactivation mechanisms of protonated aromatic amino acids following UV excitation.
Deactivation pathways of electronically excited states have been investigated in three protonated aromatic amino acids: tryptophan (Trp), tyrosine (Tyr) and phenylalanine (Phe). The protonated amino acids were generated by electrospray and excited with a 266 nm femtosecond laser, the subsequent decay of the excited states being monitored through fragmentation of the ions induced and/or enhanced by another femtosecond pulse at 800 nm. The excited state of TrpH+ decays in 380 fs and gives rise to two channels: hydrogen atom dissociation or internal conversion (IC). In TyrH, the decay is slowed down to 22.3 ps and the fragmentation efficiency of PheH+ is so low that the decay cannot be measured with the available laser. The variation of the excited state lifetime between TrpH+ and TyrH+ can be ascribed to energy differences between the dissociative pi sigma* state and the initially excited pi pi* state.
Kang
H
H
Laboratoire de Photophysique Moléculaire du CNRS, Université Paris-Sud, Bât. 210, 91405 Orsay, France. hyuk.kang@ppm.u-psud.fr
Jouvet
C
C
Dedonder-Lardeux
C
C
Martrenchard
S
S
Grégoire
G
G
Desfrançois
C
C
Schermann
J P
JP
Barat
M
M
Fayeton
J A
JA
D024322:Amino Acids, Aromatic / Q000737:chemistry*; D006859:Hydrogen / Q000737:chemistry; D007700:Kinetics; D013058:Mass Spectrometry; D008958:Models, Molecular; D011522:Protons; D014364:Tryptophan / Q000737:chemistry; D014443:Tyrosine / Q000737:chemistry; D014466:Ultraviolet Rays
D024322:Amino Acids, Aromatic; D011522:Protons; D014443:Tyrosine; D006859:Hydrogen; D014364:Tryptophan