title: Validation of experimental charge densities: refinement of the macrolide antibiotic roxithromycin.
abstract: Multipole refinements of larger organic molecules have so far been limited to a few exceptional cases. We report an investigation of the detailed experimental electron-density distribution (EDD) of roxithromycin, a macrolide antibiotic consisting of 134 atoms. Although the experimental multipole refinement on high-resolution synchrotron data converged smoothly, validation of the electron density by calculation of an `experiment minus invariom' difference density revealed conformational disorder of the H atoms. Hydrogen disorder is shown to affect the EDD, the electrostatic potential and atomic properties as defined by Bader's quantum theory of atoms in molecules. A procedure to obtain the electron density distribution in the presence of disorder is proposed.
authors.affiliation: Institut für Anorganische Chemie, Georg-August-Universität, Tammannstrasse 4, D-37077 Göttingen, Germany.
authors.forename: J J
authors.initials: JJ
authors.lastname: Holstein
authors.forename: P
authors.initials: P
authors.lastname: Luger
authors.forename: R
authors.initials: R
authors.lastname: Kalinowski
authors.forename: S
authors.initials: S
authors.lastname: Mebs
authors.forename: C
authors.initials: C
authors.lastname: Paulman
authors.forename: B
authors.initials: B
authors.lastname: Dittrich
mesh_terms: D000900:Anti-Bacterial Agents / Q000737:chemistry; D004583:Electrons; D006860:Hydrogen Bonding; D018942:Macrolides / Q000737:chemistry; D015575:Roxithromycin / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D018942:Macrolides; D015575:Roxithromycin