title: Crystal and molecular structure of the centrosymmetric meso-valinomycin analogue--cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi-L-Val-D-Hyi-D-Val-L-Hy i) (C60H102N6O18).
abstract: The crystal structure of cyclo (D-Val-D-Hyi-D-Val-L-Hyi-L-Val-D-Hyi-L-Val-L-Hyi -L-Val-D-Hyi-D-Val-L-Hyi).2H2O has been solved by x-ray direct methods. The crystals (grown from a mixture of octane/CH2Cl2) are an orthorhombic, centrosymmetric space group Pbca, cell parameters a = 11.458 (2), b = 25.613 (3), c = 23.691 (3) A, Z = 4; therefore the molecule lies on a center of inversion in the cell. The atomic coordinates for the C, N, and O atoms were refined in the anisotropic thermal motion approximation (allowing for H-atom contribution to Fcal) to a standard R-factor value of 0.081. In contrast to meso-valinomycin, the analogue under study does not adopt an octahedral cage bracelet conformation. It has an unusual centrosymmetric elongated form with two type II terminal beta-bends formed by N-H ... C=O 4-->1 type intramolecular H bonds. Two symmetry-related water molecules reside in the elongated molecular cavity of the centrosymmetric depsipeptide ring.
authors.affiliation: Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
authors.forename: V Z
authors.initials: VZ
authors.lastname: Pletnev
authors.lastname: Fonarev YuD
authors.forename: I N
authors.initials: IN
authors.lastname: Tsygannik
authors.forename: V T
authors.initials: VT
authors.lastname: Ivanov
authors.forename: S V
authors.initials: SV
authors.lastname: Pletnev
authors.forename: D A
authors.initials: DA
authors.lastname: Langs
authors.forename: W L
authors.initials: WL
authors.lastname: Duax
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D006860:Hydrogen Bonding; D007476:Ionophores / Q000737:chemistry; D008958:Models, Molecular; D015394:Molecular Structure; D013302:Streptomyces / Q000737:chemistry; D014634:Valinomycin / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: D007476:Ionophores; C077296:dodeca-valinomycin; D014634:Valinomycin