A highly stable quadruply hydrogen-bonded heterocomplex useful for supramolecular polymer blends

The butyl urea of guanosine (UG) presents an ADDA hydrogen-bonding array that is complementary to the DAAD array of 2,7-diamido-1,8-naphthyridine (DAN). The stability of the DAN.UG complex was measured by fluorimetry using the fluorescence resonance energy transfer (FRET) from the naphthyridine ring to a coumarin 343 moiety linked covalently to the UG unit. The quadruply hydrogen-bonded complex is extremely stable with a measured association constant, Kassoc, of 3 x 108 M-1. Unlike related hydrogen-bonding modules, the guanosine urea, UG, contains a relatively fixed tautomeric form and only weakly self-associates (Kdimer = ca. 200 M-1). The DAN unit was linked to a styrene-based monomer and copolymerized with styrene to form a polymer (PS-DAN) containing a controlled number of the DAAD recognition units. Likewise, a methacrylate monomer containing the UG unit was copolymerized with butyl methacrylate to form a polymer (PBMA-UG). Blends formed from PS-DAN and PBMA-UG were characterized by DSC, SEC, and viscometry. The importance of selective heterocomplexation and weak self-association in forming the blended networks was demonstrated by using a ureidopyrimidinone (UPy) unit, which also forms strong heterocomplexes with DAN but is able to strongly self-associate.     

TEOS-MTES基SiO2溶胶微结构的SAXS研究

正硅酸乙酯(TEOS)为前驱体,在碱性条件下制备含有无定形SiO2颗粒的溶胶,以甲基三乙氧基硅烷(MTES)在酸性条件下获得聚甲基硅氧链,二者混合后应用同步辐射X射线进行混合溶胶的SAXS散射强度测定,计算了溶胶的平均回转半径、平均粒径、两相界面层厚度、散射体体积分数、两相间比表面积等参数,辅以光子相关光谱法(PCS)和透射电子显微镜(TEM)观测溶胶粒度,证实SiO2颗粒被MTES混合物连接成族团.实验发现所测混合溶胶样品均表现出对Porod定理的负偏离,说明溶胶中颗粒与溶剂之间存在很明显的两相间界面层.     

Poly[tetra‐μ‐aqua‐hexa­aquadi‐μ3‐malon­ato‐dinitratodibarium(II)nickel(II)]

The title complex, [Ba₂Ni(C₃H₂O₄)₂(NO₃)₂(H₂O)₁₀]_n, has a two‐dimensional layer structure. The Ni atom lies on a crystallographic centre of symmetry in an octa­hedral NiO₆ environment, and is coordinated by four malonate O atoms in a planar arrangement and by two water mol­ecules in axial positions. The coordination of the unique Ba atom involves two nitrate O atoms, five water mol­ecules and three malonate O atoms.     

Coordination Compounds of Schiff-Base Ligands Derived from Diaminomaleonitrile (DMN): Mononuclear, Dinuclear, and Macrocyclic Derivatives

Copper(II) and V(IV)O complexes of an open chain (1:2) Schiff-base ligand (H(2)L1), derived by the template condensation of diaminomaleonitrile (DMN) and salicylaldehyde, and dicopper(II) complexes of (2:2) macrocyclic Schiff-base ligands derived by template condensation of diformylphenols and diaminomaleonitrile, have been synthesized and studied. Structures have been established for the first time for mononuclear Cu(II) and V(IV)O derivatives of the open chain ligand H(2)L1 (1:2), a dinuclear macrocyclic Cu(II) complex derived from a 2:2 macrocyclic ligand (H(2)M1), and the half-condensed 1:1 salicylaldehyde ligand (H(2)L2). [Cu(L1)] (1) (L1 = C(18)H(10)N(4)O(2)) crystallized in the monoclinic system, space group P2(1)/n (No. 14), with a = 11.753(6) ?, b = 7.708(5) ?, c = 16.820(1) ?, and Z = 4. [VO(L1)(DMSO] (2) crystallized in the orthorhombic system, space group Pbca (No. 61), with a = 22.534(9) ?, b = 23.31(1) ?, c = 7.694(5) ?, and Z = 8. H(2)L2 (C(18)H(8)N(4)O) (3) crystallized in the monoclinic system, space group P2(1)/c (No. 14), with a = 13.004(6) ?, b = 11.441(7) ?, c = 7.030(4) ?, and Z = 4. [Cu(2)(M3)](CH(3)COCH(3)) (4) (M3 = C(32)H(24)N(8)O(4)) crystallized in the monoclinic system, space group C2/c (No. 15), with a = 38.33(2) ?, b = 8.059(4) ?, c = 22.67(2) ?, and Z = 8. [Cu(L3)(DMSO)] (5) (L3 = C(20)H(14)N(2)O(4)) crystallized in the triclinic system, space group P&onemacr; (No. 2), with a = 10.236(4) ?, b = 13.514(4) ?, c = 9.655(4) ?, and Z = 2. 4 results from the unique addition of two acetone molecules to two imine sites in [Cu(2)(M1)](ClO(4))(2) (M1 = 2:2 macrocyclic ligand derived from template condensation of DMN and 2,6-diformyl-4-methylphenol). 4 has extremely small Cu-OPh-Cu bridge angles (92.0, 92.8 degrees ), well below the expected lower limit for antiferromagnetic behavior, but is still antiferromagnetically coupled (-2J = 25.2 cm(-)(1)). This behavior is associated with a possible antiferromagnetic exchange term that involves the conjugated framework of the macrocyclic ligand itself. The ligand L3 in 5 results from hydrolysis of M1 on recrystallization of [Cu(2)(M1)](ClO(4))(2) from undried dimethyl sulfoxide.     

Measurement of radioactive samples in Marinelli beakers by gamma-ray spectrometry

Radioactivity measurement of environmental samples is frequently assayed by gamma-ray spectrometry using Marinelli beakers. In this work, self-absorption and coincidence summing effects arising in activity measurements for Marinelli beaker geometry have been studied with a Ge detector. Three types of Marinelli beakers which have capacities of 450 mL, 1 L, and 2 L were developed. Self-attenuation effects for density variation of radioactive samples in each type of the Marinelli beakers were measured as a function of gamma-ray energy, and also the results were compared with calculated values by mathematical model. Meanwhile, the coincidence summing effects of¹²⁵Sb and¹⁵⁴Eu nuclides were obtained from the determination of the full-energy peak and total efficiencies for a Ge detector.     

聚醚桥连二异羟肟酸单核和双核过渡金属配合物催化PNPP水解

Two polyether bridged dihydroxamic acids and their mono-and binuclear manganese(Ⅱ), zinc(Ⅱ) complexes have been synthesized and employed as models to mimic hydrolase in catalytic hydrolysis of p-nitrophenyl picolinate (PNPP). The reaction kinetics and the mechanism of hydrolysis of PNPP have been investigated. The kinetic mathematical model for PNPP cleaved by the complexes has been proposed. The effects of the different central metal ion, mono-and binuclear metal, the pseudo-macrocyclic polyether constructed by polyethoxy group of the complexes, and reactive temperature on the rate for catalytic hydrolysis of PNPP have been examined. The results showed that the transition metal dthydroxamates exhibited high catalytic activity to the hydrolysis of PNPP, the catalytic activity of binuclear complexes was higher than that of mononuclear ones, and the pseudo-macrocyclic polyether might synergetically activate H20 coordinated to metal ion with central metal ion together and promote the catalytic hydrolysis of PNPP.     

一维链状1,8-萘二酸四核锌配位聚合物[Zn4(1,8-nap)4(4,4''-bipy)2·0.5en·H2O]n的合成、结构、热稳定性及发光性质

羧酸配位聚合物是金属离子与有机羧酸构造块通过配位键或其他分子间弱作用力经自组装而成的一维、二维、三维的聚合物.由于这些配位聚合物具有新颖的拓扑结构以及在功能材料方面的潜在应用,同时又由于羧酸配合物比较稳定,所以设计和调控特殊配位聚合物成了当前的研究热点[1～4].     

Scaffold-based molecular design with a graph generative model

Searching for new molecules in areas like drug discovery often starts from the core structures of known molecules. Such a method has called for a strategy of designing derivative compounds retaining a particular scaffold as a substructure. On this account, our present work proposes a graph generative model that targets its use in scaffold-based molecular design. Our model accepts a molecular scaffold as input and extends it by sequentially adding atoms and bonds. The generated molecules are then guaranteed to contain the scaffold with certainty, and their properties can be controlled by conditioning the generation process on desired properties. The learned rule of extending molecules can well generalize to arbitrary kinds of scaffolds, including those unseen during learning. In the conditional generation of molecules, our model can simultaneously control multiple chemical properties despite the search space constrained by fixing the substructure. As a demonstration, we applied our model to designing inhibitors of the epidermal growth factor receptor and show that our model can employ a simple semi-supervised extension to broaden its applicability to situations where only a small amount of data is available.

We propose a scaffold-based graph generative model for designing novel drug candidates that include the desired scaffold as a substructure.     

Functional involvement of src and focal adhesion kinase in a CD99 splice variant-induced motility of human breast cancer cells

Earlier report showed that expression of a splice variant of CD99 transmembrane protein increases invasive ability of human breast cancer cells. Cell motility was also significantly enhanced by the CD99 splice variant expression. In an effort to identify the cellular components that mediate a signal transduction pathway triggered by the CD99 splice variant, known signal path inhibitors were examined for their effects on the motility of the CD99 splice variant-transfected MDA-MB-231 breast cancer cells. Phenylarsine oxide, an inhibitor of phosphatase specific for focal adhesion kinase, and PP1, an inhibitor of src kinase family, significantly suppressed motility of the cells. Among different types of src transfectant clones generated, kinase-negative mutant src transfectant cells were 80% less motile than the mock cells transfected with an empty-vector, while v-src and c-src transfectants exhibited cell motility levels at or slightly above the mock transfectant. These results suggest that src and focal adhesion kinase mediate the intracellular signaling pathway of a CD99 splice variant for the induction of motility of human breast cancer cells.