Modeling the tyrosine-sugar interactions in supersonic expansions: glucopyranose-phenol clusters.

Sugars are fundamental building blocks for living organisms and their interaction with proteins plays a central role in fundamental biological processes, such as energy storage and production, post-transductional modifications or immune response. Understanding those processes require deep knowledge of the forces that drive the interactions at the molecular level. Here we explore the interactions between α/β-methyl-d-glucopyranose and β-phenyl-d-glucopyranose with phenol, and the chromophore of tyrosine, using a combination of mass-resolved laser electronic spectroscopy in supersonic expansions and quantum mechanical calculations. The structures of the complexes detected in the jet are stabilized by a subtle equilibrium between several types of weak interactions, among which the dispersion forces may tilt the balance. In particular, the small structural changes introduced by the orientation of the anomeric substituent are amplified by the interaction with phenol. Consequently, the number of conformational isomers detected experimentally is different for each system and they present also differences in the preferred solvation site. Furthermore, inclusion of entropic terms for the calculated structures is advisable to understand the energetic reasons for the detection of a small set of experimental conformational isomers.