title: Direct observation of hydrogen atom dynamics and interactions by ultrahigh resolution neutron protein crystallography.
abstract: The 1.1 Å, ultrahigh resolution neutron structure of hydrogen/deuterium (H/D) exchanged crambin is reported. Two hundred ninety-nine out of 315, or 94.9%, of the hydrogen atom positions in the protein have been experimentally derived and resolved through nuclear density maps. A number of unconventional interactions are clearly defined, including a potential O─H…π interaction between a water molecule and the aromatic ring of residue Y44, as well as a number of potential C─H…O hydrogen bonds. Hydrogen bonding networks that are ambiguous in the 0.85 Å ultrahigh resolution X-ray structure can be resolved by accurate orientation of water molecules. Furthermore, the high resolution of the reported structure has allowed for the anisotropic description of 36 deuterium atoms in the protein. The visibility of hydrogen and deuterium atoms in the nuclear density maps is discussed in relation to the resolution of the neutron data.
authors.affiliation: Department of Chemistry, University of Toledo, Toledo, OH 43606, USA. julian.ch.chen@gmail.com
authors.forename: Julian C-H
authors.initials: JC
authors.lastname: Chen
authors.forename: B Leif
authors.initials: BL
authors.lastname: Hanson
authors.forename: S Zoë
authors.initials: SZ
authors.lastname: Fisher
authors.forename: Paul
authors.initials: P
authors.lastname: Langan
authors.forename: Andrey Y
authors.initials: AY
authors.lastname: Kovalevsky
mesh_terms: D016880:Anisotropy; D001671:Biochemistry / Q000379:methods; D001937:Brassica / Q000378:metabolism; D003460:Crystallization; D003461:Crystallography / Q000379:methods*; D003903:Deuterium / Q000737:chemistry; D006859:Hydrogen / Q000737:chemistry*; D006860:Hydrogen Bonding; D046911:Macromolecular Substances; D008968:Molecular Conformation; D033363:Neutron Diffraction / Q000379:methods; D009502:Neutrons; D010940:Plant Proteins / Q000737:chemistry*; D012997:Solvents / Q000737:chemistry; D014867:Water / Q000737:chemistry
chemical_list: D046911:Macromolecular Substances; D010940:Plant Proteins; D012997:Solvents; D014867:Water; C024934:crambin protein, Crambe abyssinica; D006859:Hydrogen; D003903:Deuterium