title: Extended X-ray absorption fine structure (EXAFS) investigations of model compounds for zinc enzymes.
abstract: A test of the ability of extended X-ray absorption fine structure (EXAFS) to determine structural information with specific reference to zinc sites in enzymes has been made. X-ray absorption spectra of 18 compounds of zinc have been measured and the nearest-neighbour scattering has been interpreted using a Fourier transform and an ab initio technique. Empirical Zn-N, Zn-O, Zn-S and Zn-Cl amplitude and phase functions have been extracted from Zn(C3H4N2)4(ClO4)2, ZnO, Zn(S2COC2H5)2 and [N(CH3)4]2[ZnCl4], respectively and tabulated as a function of the wavevector with respect to 9660.0 eV X-ray energy. These amplitude and phase functions were then tested with respect to the other 14 compounds. For a single species of atoms in the first coordination shell the interatomic distances can be established to +/- 0.5 pm (+/- 5 x 10(-3) A) whilst when mixed shells exist errors in distances are +/-4 pm (+/- 40 x 10(-3) A). Coordination numbers are given to +/- 16% for the single species case a and +/- 25% for the mixed coordination case. Using the theoretical amplitude and phase functions of McKale et al. [(1988) J. Am. Chem. Soc. 110, 3763-3768] the deduced distances are systematically too small by an average of 0.6 pm (6 x 10(-3) A). The errors in the coordination numbers are 18%.
authors.affiliation: Anorganisch-Chemisches Institut, Westfälische Wilhelms-Universität, Münster, Federal Republic of Germany.
authors.forename: P
authors.initials: P
authors.lastname: Eggers-Borkenstein
authors.forename: S
authors.initials: S
authors.lastname: Priggemeyer
authors.forename: B
authors.initials: B
authors.lastname: Krebs
authors.forename: G
authors.initials: G
authors.lastname: Henkel
authors.forename: U
authors.initials: U
authors.lastname: Simonis
authors.forename: R F
authors.initials: RF
authors.lastname: Pettifer
authors.forename: H F
authors.initials: HF
authors.lastname: Nolting
authors.forename: C
authors.initials: C
authors.lastname: Hermes
mesh_terms: D004798:Enzymes / Q000378:metabolism*; D008433:Mathematics; D008667:Metalloproteins / Q000378:metabolism*; D008962:Models, Theoretical; D013057:Spectrum Analysis / Q000379:methods; D014965:X-Rays; D015032:Zinc
chemical_list: D004798:Enzymes; D008667:Metalloproteins; D015032:Zinc