Ultrafast light-induced dynamics in the microsolvated biomolecular indole chromophore with water

Abstract

Interactions between proteins and their solvent environment can be studied in a bottom-up approach using hydrogen-bonded chromophore-solvent clusters. The ultrafast dynamics following UV-lightinduced electronic excitation of the chromophores, potential radiation-damage, and their dependence on solvation are important open questions. The microsolvation effect is challenging to study due to the inherent mix of the produced gas-phase aggregates. We used the deflector to spatially separate different molecular species in combination with pump-probe velocity-map-imaging experiments. We demonstrated that this powerful experimental approach reveals intimate details of the UV-induced dynamics in the near-UV-absorbing prototypical biomolecular indole-water system. We determined the time-dependent appearance of the different reaction products and disentangled the occurring ultrafast processes. This novel approach ensures that the reactants are well-known and that detailed characteristics of the specific reaction products are accessible -paving the way for the complete chemical-reactivity experiment.

Water is a radiation protection agent for ionised pyrrole

“…The radiation protection mechanisms for excited chromophores were studied both experimentally and theoretically. 55,56,61,62,83 Our study showed that this protective effect observed for solvated chromophores is also valid after ionisation.…”

“…53 Pyrrole is also a subunit of indole, 3-methylindole, and tryptophan, which are of great relevance as the principal UV absorbers of proteins. 54,55 The photophysical and photochemical properties of indole and pyrrole are sensitive to the hydration environment: [56][57][58][59][60][61] upon UV absorption these chromophores indirectly populate an excited 1 ps* state, which is repulsive along the N-H-stretching coordinate. [54][55][56] This triggers an ultrafast internal-conversion process to the ground state, essential for the photostability of proteins.…”

Specific versus non-specific interactions of indole in water revealed by x-ray photoemission spectroscopy

“…The influence of solvation on indole's electronic structure has long been debated [6], in particular with respect to its two lowest-energy 1 L a and 1 L b electronically excited singlet states [7][8][9]. Microsolvation experiments with one or a few water molecules attached have shed some light onto this topic [10][11][12][13].…”

Active learning of potential-energy surfaces of weakly bound complexes with regression-tree ensembles

“…4 They offer an appealing way for the quantitative investigations of the effects of hydration on the photoexcitation and ionization dynamics and the mechanisms of chemical reactions in general. [5][6][7][8][9][10] First principles calculations of potential energy surfaces (PESs) for weakly-bound complexes are challenging and computationally expensive. [11][12][13][14] The presence of small energy differences in weakly-bound PES means that generally high levels of theory need to be employed to produce correct asymptotic behavior.…”