title: The X-ray structure of the monoclinic crystal form of [D-Hyi2, L-Hyi4] meso-valinomycin.
abstract: The conformation and intermolecular association of [D-Hyi2, L-Hyi4] meso-valinomycin [cyclo[-D-Val-D-Hyi-L-Val-L-Hyi-(D-Val-L-Hyi-L-Val-D-+ ++Hyi)2-], C60H102N6O18] in a crystal form obtained from ethanol solution has been determined by x-ray crystallography. Two depsipeptides and one ethanol molecule per asymmetric unit crystallize in space group P2(1) (Z = 4); a = 14.579, b = 39.795, c = 13.928 A, beta = 116.90, Rl = 0.0757. The molecular conformation is very similar to that observed in the trigonal P3(2) crystal form obtained from acetone solution [V. Z. Pletnev et al. (1991) Biopolymers, Vol. 31, pp. 409-415]. Both independent molecules in the crystal adopt a similar distorted bracelet structure with a sterically inaccessible, partially formed, ion-binding center that is stabilized by six 4-->1 type H bonds. The observed conformation accounts for the inability of the molecule to complex ions. Close examination of the three crystallographically independent molecules reveals that differences in the backbone conformation associated with solvent interaction are significantly larger than those associated with hydrophobic van der Waals interactions of crystal packing.
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.forename: V T
authors.initials: VT
authors.lastname: Ivanov
authors.forename: D A
authors.initials: DA
authors.lastname: Langs
authors.forename: B M
authors.initials: BM
authors.lastname: Burkhart
authors.forename: W L
authors.initials: WL
authors.lastname: Duax
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D008968:Molecular Conformation; D014634:Valinomycin / Q000031:analogs & derivatives* / Q000737:chemistry
chemical_list: C077296:dodeca-valinomycin; D014634:Valinomycin