Specific versus Nonspecific Solvent Interactions of a Biomolecule in Water
Lanhai He, Lukáš Tomaník, Sebastian Malerz, Florian Trinter, Sebastian Trippel, Michal Belina, Petr Slavı́ček, Bernd Winter, Jochen Küpper
Abstract
High Resolution Image Download MS PowerPoint Slide Solvent interactions, particularly hydration, are vital in chemical and biochemical systems. Model systems reveal microscopic details of such interactions. We uncover a specific hydrogen-bonding motif of the biomolecular building block indole (C 8 H 7 N), tryptophan’s chromophore, in water: a strong localized N–H···OH 2 hydrogen bond, alongside unstructured solvent interactions. This insight is revealed from a combined experimental and theoretical analysis of the electronic structure of indole in aqueous solution. We recorded the complete X-ray photoemission and Auger spectrum of aqueous-phase indole, quantitatively explaining all peaks through ab initio modeling. The efficient and accurate technique for modeling valence and core photoemission spectra involves the maximum-overlap method and the nonequilibrium polarizable-continuum model. A two-hole electron-population analysis quantitatively describes the Auger spectra. Core–electron binding energies for nitrogen and carbon highlight the specific interaction with a hydrogen-bonded water molecule at the N–H group and otherwise nonspecific solvent interactions.