Pletnev V Z, Ivanov V T, Langs D A, Burkhart B M, Duax W L
Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, Moscow, Russia.
Biopolymers. 1997 Nov;42(6):645-50. doi: 10.1002/(SICI)1097-0282(199711)42:6<645::AID-BIP3>3.0.CO;2-U.
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.
通过X射线晶体学确定了从乙醇溶液中获得的晶体形式的[D-Hyi2，L-Hyi4]内消旋缬氨霉素[环[-D-缬氨酸-D-Hyi-L-缬氨酸-L-Hyi-(D-缬氨酸-L-Hyi-L-缬氨酸-D-Hyi)2-]，C60H102N6O18]的构象和分子间缔合。每个不对称单元中的两个缩肽和一个乙醇分子在空间群P2(1)（Z = 4）中结晶；a = 14.579，b = 39.795，c = 13.928 Å，β = 116.90，Rl = 0.0757。分子构象与从丙酮溶液中获得的三角P3(2)晶体形式中观察到的非常相似[V. Z. Pletnev等人（1991年），《生物聚合物》，第31卷，第409 - 415页]。晶体中的两个独立分子都采用类似的扭曲手镯结构，具有一个空间上无法接近的、部分形成的离子结合中心，该中心通过六个4→1型氢键得以稳定。观察到的构象解释了该分子无法络合离子的原因。对三个晶体学独立分子的仔细检查表明，与溶剂相互作用相关的主链构象差异明显大于与晶体堆积的疏水范德华相互作用相关的差异。
