title: Molecular conformation of a D,L stereoisomeric analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D-Hyi)-].
abstract: The crystal structure of a synthetic analogue of valinomycin, cyclo[-(L-Val-L-Hyi-L-Val-D-Hyi)2-(D-Val-L-Hyi-L-Val-D -Hyi)-] ([L-Val1, L-Val5]meso-valinomycin), C60H102N6O18, has been determined. Crystals grown from petroleum ether are orthorhombic, space group P2(1)2(1)2(1), with cell parameters a = 16.41(1), b = 18.76(1), c = 25.86(1) A, and Z = 4. The atomic coordinates for nonhydrogen atoms, except those of terminal carbons on one side chain, were refined in the anisotropic thermal motion approximation. The coordinate parameters of the H atoms were incorporated into the structure factor calculations at geometrically expected positions. Values of the standard and weighted R factors after refinement are 0.074 and 0.083, respectively. The crystal structure of the molecule is asymmetric and adopts a conformation with four 4----1 type and one 6----1 type intramolecular hydrogen bonds between amide nitrogens and carbonyl oxygens. Valinomycin binds potassium more than 100 times strongly than the D,L stereoisomeric analogue, as a result of a different spatial orientation of potentially interacting carbonyl groups.
authors.affiliation: Medical Foundation of Buffalo, New York 14203.
authors.forename: D A
authors.initials: DA
authors.lastname: Langs
authors.forename: P
authors.initials: P
authors.lastname: Grochulski
authors.forename: W L
authors.initials: WL
authors.lastname: Duax
authors.forename: V Z
authors.initials: VZ
authors.lastname: Pletnev
authors.forename: V T
authors.initials: VT
authors.lastname: Ivanov
mesh_terms: D000595:Amino Acid Sequence; D008958:Models, Molecular; D008969:Molecular Sequence Data; D011487:Protein Conformation; D014634:Valinomycin / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D014634:Valinomycin