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861.
Gene‐Hsiang Lee Hsin‐Ta Wang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(5):m216-m219
N,N′‐Bis(4‐pyridylmethyl)oxalamide, C14H14N4O2, exists as a dimer which is extended into a two‐dimensional network with other dimers through pyridine–amide hydrogen bonds. The crystal structure of the title coordination polymer, {[CoCl2(C14H14N4O2)]·0.5H2O}n, features a one‐dimensional zigzag chain, in which the cobalt ion sits at a twofold symmetry position and adopts a tetrahedral geometry, and the bridging ligand lies on an inversion center and connects to CoII ions in a bis‐monodentate mode. Furthermore, two interwoven chains create a cavity of ca 8.6 × 8.6 Å, which produces a three‐dimensional channel. Water molecules are held in the channel by hydrogen bonds. 相似文献
862.
Chun‐Xiang Wang Zhi‐Feng Li Ping Wang 《Acta Crystallographica. Section C, Structural Chemistry》2007,63(11):m473-m475
In the title compound, [Nd2(C4H4O4)2(C2O4)(H2O)2]n, the flexible succinate anion assumes the gauche conformation and bridges the nine‐coordinate Nd atoms to generate two‐dimensional layers parallel to (010). The coordination polymer layers are linked into a three‐dimensional framework by the rigid oxalate ligands. The oxalate ions are located on a center of inversion. 相似文献
863.
Ming‐Zhong Wang Yan‐Yan Zhang Shun‐Lin Li Xiang‐Hai Cai Xiao‐Dong Luo 《Helvetica chimica acta》2006,89(12):3104-3108
A new norsesquiterpene named eupatorone (= (4S,4aR,6R)‐1‐acetyl‐6‐(acetyloxy)‐4,4a,5,6‐tetrahydro‐4,7‐dimethylnaphthalen‐2(3H)‐one; 1 ) and a new sesquiterpene derivative named 2‐deoxo‐2‐(acetyloxy)‐9‐oxoageraphorone (= (1R,4S,4aR,6R,8aS)‐6‐(acetyloxy)‐3,4,4a,5,6,8a‐hexahydro‐4,7‐dimethyl‐1‐(1‐methylethyl)naphthalen‐2(1H)‐one; 2 ), together with the five known cadinene derivatives 3 – 7 were isolated from the flower of Eupatorium adenophorum (Spreng. ). Their structures were established by extensive NMR experiments, including 1D and 2D NMR. 相似文献
864.
Wolfgang Dietzsch Norman V. Duffy Aaron M. Lee Brian W. Skelton Allan H. White 《无机化学与普通化学杂志》2006,632(15):2419-2423
The consequences of replacement of the symmetrically chelate ligands in [M(E2CNR2)3] (E = S, Se) complexes of potential 32 symmetry by analogous mixed S,Se unsymmetrical chelates are explored for both small (M = Co) and large (M = In) metal atoms, and R = primary (Et) and secondary (iPr) alkyl substituents by way of low‐temperature single crystal X‐ray studies of [(Co(SSeCNEt2)3] ([Co(Se2CNEt2)3] also determined as datum), and [In(SSeCNR2)3], R = Et, iPr. The structure of [(iPr2N·CS·Se)2] is also recorded. 相似文献
865.
Chun‐Xiang Wang Chen‐Xia Du Zhi‐Feng Li 《Acta Crystallographica. Section C, Structural Chemistry》2006,62(10):m488-m490
In the title compound, [Zn(C17H10N5O)2(H2O)2]·4H2O, cyclic water hexamers forming one‐dimensional metal–water chains are observed. The water clusters are trapped by the co‐operative association of coordination interactions and hydrogen bonds. The ZnII ion resides on a centre of symmetry and is in an octahedral coordination environment comprising two O atoms and two N atoms from two 2′‐(4,5‐diazafluoren‐9‐ylidene)picolinohydrazidate ligands and two water molecules. 相似文献
866.
Layer-by-layer fluorescent conjugated polyelectrolyte films have been studied. The photoluminescence of conjugate polyelectrolytes was observed to be highly tunable during this film assembly process. Efficient photoinduced electron transfer from thus prepared highly luminescent film to a natural electron-transfer protein cytochrome c has also been observed. 相似文献
867.
Sadowsky JD Schmitt MA Lee HS Umezawa N Wang S Tomita Y Gellman SH 《Journal of the American Chemical Society》2005,127(34):11966-11968
Molecules that bind to specific surface sites on proteins are of great interest from both fundamental and practical perspectives. We are exploring a ligand development strategy that is based on oligomers with discrete folding propensities ("foldamers"); we target a specific cleft on the cancer-associated protein Bcl-xL because this system is well characterized structurally. In vivo, this cleft binds to alpha-helical segments (BH3 domains) of other proteins. We evaluated several types of helical foldamer, built entirely from beta-amino acid residues or from mixtures of alpha- and beta-amino acid residues, and ultimately identified foldamers in the latter class that bind very tightly to Bcl-xL. Our results suggest that combining different types of foldamer backbones will be an effective and general strategy for creating high-affinity and specific ligands for protein surface sites. 相似文献
868.
Three new alkaloids, longistylumphyllines A–C (1–3), together with the six known alkaloids deoxycalyciphylline B, deoxyisocalyciphylline B, methyl homosecodaphniphyllate, daphnicyclidin A, daphnicyclidin B, and daphnicyclidin F, were isolated from the stems and leaves of Daphniphyllum longistylum. Their structures and relative configuration were elucidated on the basis of spectroscopic data, especially 1D and 2D NMR techniques. 相似文献
869.
Implicit solvent methods have become popular tools in the field of protein dynamics simulations, yet evaluation of their validity has been primarily limited to comparisons with experimental and theoretical data for small molecules. In this paper, we use a recently developed hybrid explicit/implicit solvent methodology to evaluate the accuracy of several Poisson-based implicit solvent models. Specifically, we focus on the calculation of electrostatic solvation free energies of various fixed conformations for two proteins. We show that, among various dielectric boundary definitions, the Lee-Richards molecular surface has the best agreement with hybrid solvent results. Furthermore, certain modifications of the molecular surface Poisson protocol provide varied results. For instance, simple modifications of atomic radii on charged residues generally improve absolute errors but do not significantly reduce relative errors among conformations. On the other hand, using a water-probe radius of 1.0 A, as opposed to the standard value of 1.4 A, to generate the molecular surface, moderately improves both absolute and relative results. 相似文献
870.