title: Magnetic effects of disulfide bridges: a density functional and semiempirical study.
abstract: Density functional chemical shielding calculations are reported for methane and hydrogen disulfide dimers. The calculations show that the contributions of disulfide bridges to the chemical shielding of neighboring protons is sizable at distances that are frequently sampled in protein structures. A semiempirical model of the quantum chemical data is developed. It is shown that magnetic anisotropy effects of disulfide are poorly described by the McConnell equation, both qualitatively and quantitatively. In particular, the ratio of magnetic anisotropy contributions to shielding along and perpendicular to the magnetic anisotropy principal axis do not conform to the predictions of the McConnell equation, and magnetic anisotropy effects are not null along the magic angle axis. A sulfur-based model of the magnetic anisotropy of the disulfide is developed and shown to give much better agreement with the quantum chemical data.
authors.affiliation: UMR7104, Structural Biology and Genomics Laboratory, Institut de Génétique et de Biologie Moléculaire et Cellulaire, CNRS/INSERM/ULP, BP 10142, F-67404 Illkirch Cedex, France.
authors.forename: Finton
authors.initials: F
authors.lastname: Sirockin
authors.forename: Annick
authors.initials: A
authors.lastname: Dejaegere
mesh_terms: D016880:Anisotropy; D002627:Chemistry, Physical / Q000379:methods*; D019281:Dimerization; D004220:Disulfides / Q000737:chemistry; D006862:Hydrogen Sulfide / Q000737:chemistry; D008280:Magnetics; D015233:Models, Statistical; D008968:Molecular Conformation; D016011:Normal Distribution; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D012984:Software
chemical_list: D004220:Disulfides; D011506:Proteins; D011522:Protons; D006862:Hydrogen Sulfide