title: Hydration of sugars in the gas phase: regioselectivity and conformational choice in N-acetyl glucosamine and glucose.
abstract: The influence of an acetamido group in directing the preferred choice of hydration sites in glucosamine and a consequent extension of the working rules governing regioselective hydration and conformational choice, have been revealed through comparisons between the conformations and structures of "free" and multiply hydrated phenyl N-acetyl-beta-D-glucosamine (betapGlcNAc) and phenyl beta-D-glucopyranoside (betapGlc), isolated in the gas phase at low temperatures. The structures have been assigned through infrared ion depletion spectroscopy conducted in a supersonic jet expansion, coupled with computational methods. The acetamido motif provides a hydration focus that overwhelms the directing role of the hydroxymethyl group; in multiply hydrated betapGlcNAc the water molecules are all located around the acetamido motif, on the "axial" faces of the pyranose ring rather than around its edge, despite the equatorial disposition of all the hydrophilic groups in the ring. The striking and unprecedented role of the C-2 acetamido group in controlling hydration structures may, in part, explain the differing and widespread roles of GlcNAc, and perhaps GalNAc, in nature.
authors.affiliation: Chemistry Department, University of Oxford, Physical and Theoretical Chemistry Laboratory, South Parks Road, Oxford OX1 3QZ, UK.
authors.forename: Emilio J
authors.initials: EJ
authors.lastname: Cocinero
authors.forename: E Cristina
authors.initials: EC
authors.lastname: Stanca-Kaposta
authors.forename: Mark
authors.initials: M
authors.lastname: Dethlefsen
authors.forename: Bo
authors.initials: B
authors.lastname: Liu
authors.forename: David P
authors.initials: DP
authors.lastname: Gamblin
authors.forename: Benjamin G
authors.initials: BG
authors.lastname: Davis
authors.forename: John P
authors.initials: JP
authors.lastname: Simons
mesh_terms: D000117:Acetylglucosamine / Q000737:chemistry*; D002241:Carbohydrates / Q000737:chemistry*; D005740:Gases; D005947:Glucose / Q000737:chemistry*; D006860:Hydrogen Bonding; D008958:Models, Molecular; D008968:Molecular Conformation; D013329:Structure-Activity Relationship
chemical_list: D002241:Carbohydrates; D005740:Gases; D005947:Glucose; D000117:Acetylglucosamine