Comprehensive characterization of the photodissociation pathways of protonated tryptophan

Abstract

The photofragmentation of protonated tryptophan has been investigated in a unique experimental setup, in which ion and neutral issued from the photofragmentation are detected in coincidence, in time and in position. From these data are extracted the kinetic energy, the number of neutral fragments associated with an ion, their masses, and the order of the fragmentation steps. Moreover, the fragmentation time scale ranging from tens of nanoseconds to milliseconds is obtained. From all these data, a comprehensive fragmentation mechanism is proposed.

Photodissociation of protonated tryptamine and its supramolecular complex with 18-crown-6 ether: Dissociation times and channels, absorption spectra, and excited states calculations

“…As the energy distribution depletes from the high-energy side, other dissociation channels may take over, and the decay is therefore less steep than the case where one channel dominates over the whole energy range. In agreement with these findings, when photoexcitation was done inside the Zajfman trap, two ions were clearly separated in time after four oscillations corresponding to Try +Å and non-irradiated TryH + ions (the same has been observed for TrpH + [2]). …”

“…Ions were trapped inside a hexapole for one millisecond and then accelerated to kinetic energies of 2.5 keV as described previously [2]. Ion bunches of 100 ns time width produced at a 1 kHz repetition rate were selected by an electrical chopper.…”

“…UV irradiation leads to excitation of the indole chromophore (a pp * transition) followed by several competing deactivation pathways [1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Internal conversion back to the ground state and intramolecular vibrational redistribution of the energy results in a vibrationally hot ion that dissociates on the nanosecond time scale.…”

UV photoinduced dynamics in protonated aromatic amino acid

“…As it will be seen the full interpretation of such a complex signal requires much more information than just the lifetime measurement 11 . In particular it should require what are the possible fragmentation mechanisms and the parent/daughter ion links that have been obtained very recently with the experiment presented above 8, 9 .…”

“…Nanosecond UV spectroscopy on protonated molecules [4][5][6] in which the fragmentation yield as a function of the excitation wavelength has been investigated. Coincidence experiments allow to identify the neutral fragment(s) associated with a particular ionic channel [7][8][9] which imposes severe constraints on the possible fragmentation mechanisms. Moreover, it has been possible to extract the fragmentation times which are less than 10 ns for all primary fragmentation channels and in the µs range for some secondary fragment.…”