Isolating the spectroscopic signature of a hydration shell with the use of clusters: superoxide tetrahydrate

Cluster spectroscopy, aided by ab initio theory, was used to determine the detailed structure of a complete hydration shell around an anion. Infrared spectra of size-selected O(2)-. (H(2)O)(n) (n = 1 to 4) cluster ions were obtained by photoevaporation of an argon nanomatrix. Four water molecules are required to complete the coordination shell. The simple spectrum of the tetrahydrate reveals a structure in which each water molecule is engaged in a single hydrogen bond to one of the four lobes of the pi* orbital of the superoxide, whereas the water molecules bind together in pairs. This illustrates how water networks deform upon accommodating a solute ion to create a distinct supramolecular species.     

新型间硝基苯甲酸稀土配位聚合物[Nd2（C7H4O4N）7H2O]n的水热合成和晶体结构

采用水热方法合成出一种新型的间硝基苯甲酸稀土配位聚合物[Nd2（C7H4O4N）7H2O]n,并通过元素分析、红外光谱、X射线单晶结构分析对该配位聚合物进行了表征.标题配位聚合物的晶体属于三斜晶系,P1空间群,晶胞参数a=0.984 8（2）nm,b=1.131 4（2）nm,c=1.366 3（3）nm,α=69.22（3）,°β=82.48（3）°,γ=82.21（3）°,V=1.404 5（5）nm3,Dc=1.806 g/cm3,Z=1.结构分析表明：标题化合物是由稀土金属Nd（Ⅲ）和间硝基苯甲酸组成的配位聚合物,此聚合物通过Ln—O—C—O—Ln形成无限一维链状结构,进一步又通过分子间氢键连接形成复杂的三维氢键网络结构.     

一维链状镍配合物[Ni（C_（14）H_（10）N_2O_2）（Mf）]_n的合成和晶体结构

合成了含水杨醛缩苯甲酰腙的一维链状镍配合物[Ni（C14H10N2O2）（Mf）]n（Mf=C4H9NO,即吗啡啉）,通过元素分析,红外、电子光谱和X-射线单晶衍射进行了表征.晶体属单斜晶系,空间群为P21/c,a=0.9708（4）nm,b=1.4783（7）nm,c=1.2275（4）nm,β=95.728（14）°,V=1.7528（12）nm3,Z=4,Mr=384.07,Dc=1.455 g.cm-3,μ=1.129 mm-1,F（000）=800,R=0.0759,wR=0.2155.中心镍离子与水杨醛缩苯甲酰腙配体提供的2个氧原子与1个氮原子以及1个配位吗啡啉的氮原子配位,形成了N2O2的平面四边形的配位构型.晶体内每个配合物分子通过分子间氢键与相邻另一个配合物分子缔合成一个沿c轴方向的一维链状结构,N…N氢键键长为0.3239（10）nm,N-H…N氢键键角为173.56°.     

Crystal structure of a complex of acridine, cytosine and water (1:1:1)

X-ray structural analysis of a crystalline complex between acridine C(13)H(9)N, cytosine C(4)H(5)N(3)O, and water (1:1:1) has been completed. The cytosine and water molecules form a sheet-like structure through a series of hydrogen bonds. The acridine molecules are bound to this layer through a hydrogen bridge from the water to the ring nitrogen. The acridine molecules stack in a parallel fashion normal to the cytosine-water sheets, with an average interplanar spacing of 3.5 angstroms.     

A chemically functionalizable nanoporous material

Although zeolites and related materials combine nanoporosity with high thermal stability, they are difficult to modify or derivatize in a systematic way. A highly porous metal coordination polymer [Cu3(TMA)2(H2O)3]n (where TMA is benzene-1,3,5-tricarboxylate) was formed in 80 percent yield. It has interconnected [Cu2(O2CR)4] units (where R is an aromatic ring), which create a three-dimensional system of channels with a pore size of 1 nanometer and an accessible porosity of about 40 percent in the solid. Unlike zeolites, the channel linings can be chemically functionalized; for example, the aqua ligands can be replaced by pyridines. Thermal gravimetric analysis and high-temperature single-crystal diffractometry indicate that the framework is stable up to 240 degreesC.     

Cytidylic acid "a" trihydrate: structure and conformation

Cytidylic acid "a" (cytidine 2'-monophosphate) crystallizes in the triclinic space group P1 with two molecules of cytidine monophosphate (C(9)H(14)O(8)N(3)P) and six molecules of water in the unit cell. X-ray analysis of this crystal shows that in both molecules, the base is in the anti conformation, the ribose ring is C(2')-endo puckered, and the hydroxyl O(5') is gauche-gauche. The two molecules are linked by a short hydrogen bond through the phosphate oxygens.     

Large-area three-dimensional molecular ordering of a polymer brush by one-step processing

Rational molecular design and processing, enabling large-area molecular ordering, are important for creating high-performance organic materials and devices. We show that, upon one-step hot-pressing with uniaxially stretched Teflon sheets, a polymer brush carrying azobenzene-containing mesogenic side chains self-assembles into a freestanding film, where the polymer backbone aligns homeotropically to the film plane and the side chains align horizontally. Such an ordered structure forms through translation of a one-dimensional molecular order of the Teflon sheet and propagates from the interface macroscopically on both sides of the film. The resultant wide-area bimorph configuration allows the polymer film to bend rapidly and reversibly when the azobenzene units are photoisomerized. The combination of polymer brushes with hot-pressing and Teflon sheets provides many possibilities in designing functional soft materials.     

微胚乳玉米抗旱性研究

以普通玉米正大619和Y1为对照种,研究微胚乳玉米组合MEM1、MEM2、MEM3、MEM4叶片丙二醛含量、相对电导率、ASI和抗旱指数,对微胚乳玉米进行抗旱性鉴定。结果表明：在较肥土壤和瘠薄土壤里,由干旱胁迫引起的微胚乳玉米叶片丙二醛含量、ASI、相对电导率的变化规律与普通玉米一致。MEM1和MEM3在较肥土壤和瘠薄土壤里都表现出较好的抗旱性,综合抗旱性仅次于正大619。     

Rhodizite: structure and composition

The mineral rhodizite could not be assigned a chemical formula on the basis of chemical analyses. The solution of the crystal structure reported here reveals that CsB(12)Be(4)Al(4)O(28) is the ideal formula. The oxygen atoms occupy all but four sites per cell of cubic close packing whose period is (1/2)a. The boron, beryllium, and aluminum atoms occupy interstices of this array, the first two in tetrahedral coordination, the last in octahedral coordination. Together these atoms form a continuous network whose composition is B(12)Be(4)Al(4)O(28), which should be neutral. The alkali atom is enclosed in a cage in this network and presumably is not behaving as an ion.     

Reversible concerted ligand substitution at alternating metal sites in an extended solid

We report a synthetic material, [Co2(bipy)3(SO4)2(H2O)2](bipy) (CH3OH), (1, where bipy = 4,4'-bipyridyl) that contains discrete reactive and inert structural motifs that undergo a reversible substitution reaction involving the concerted and spatially controlled introduction of bipyridine and methanol molecules at the reactive sites. This reaction defines the pore geometry of the resulting open-framework structure and controls the manner in which this structure sorbs small molecules. The molecules involved in the reaction are positioned by an array of well-defined interactions during their path to binding to the metal centers.     

Methanobactin, a copper-acquisition compound from methane-oxidizing bacteria

Siderophores are extracellular iron-binding compounds that mediate iron transport into many cells. We present evidence of analogous molecules for copper transport from methane-oxidizing bacteria, represented here by a small fluorescent chromopeptide (C45N12O14H62Cu, 1216 daltons) produced by Methylosinus trichosporium OB3b. The crystal structure of this compound, methanobactin, was resolved to 1.15 angstroms. It is composed of a tetrapeptide, a tripeptide, and several unusual moieties, including two 4-thionyl-5-hydroxy-imidazole chromophores that coordinate the copper, a pyrrolidine that confers a bend in the overall chain, and an amino-terminal isopropylester group. The copper coordination environment includes a dual nitrogen- and sulfur-donating system derived from the thionyl imidazolate moieties. Structural elucidation of this molecule has broad implications in terms of organo-copper chemistry, biological methane oxidation, and global carbon cycling.     

Amorphous solid water: a neutron diffraction study

The structure factor of amorphous solid D(2)O deposited from the vapor at 10 degrees K has been obtained by measuring the neutron diffraction spectrum in the wave vector transfer from 0.8 to 12.3 reciprocal angstroms. The results indicate that the phase investigated is amorphous and has a liquiid-like structure factor. The Fourier-transformed structure e factor yields a real space pair distribution function consistent with local tetrahedral coordination and hydrogen bonding, as in other condensed phases of water. The intramolecular OD separation is 1.00 angstrom; the lack of data for very large wave vector transfer and the expected near equality of the intramolecular DD separation and intermolecular O . . . D separation make it impossible to determine the intramolecular DOD angle with precision. The neutron scattering data presented are complementary to the x-ray diffraction studies of Venkatesh, Rice, antd Narten.     

Boron-Oxygen Polyanion in the Crystal Structure of Tunellite

The crystal structure of tunellite, SrO.3B(2)O(3).4H(2)O, with infinite sheets of composition n[B(6)O(9)(OH)(2)](2-), has cations and water molecules in the spaces within the sheets. Adjacent sheets are held together by hydrogen bonding through the water molecules. The boron-oxygen polyanions provide the first example in hydrated borate crystals of one oxygen linked to three borons.     

甘氨酸亚铁的合成和晶体结构研究

以甘氨酸和七水硫酸亚铁为原料合成了甘氨酸亚铁。采用溶剂挥发法得到了晶体,并通过红外谱图和X-射线单晶衍射确定了晶体的结构。化合物属于三斜晶系,空间群P-1,晶胞参数:a=0.59949(3)nm,b=0.67626(4)nm,c=1.33192(6)nm,α=85.453(4)°,β=82.914(4)°,γ=83.115(5)°,V=0.53085(5)nm3,C4H30N2O22Fe2S2,Mr=634.12,Z=1,R1=0.0219,wR2=0.0640[I>2σ(I)],S=1.005。化合物中铁(Ⅱ)配位数为6,配位多面体为变形的八面方体构型。结构式为 。     

混合培养基用于提高犬瘟热病毒在细胞上的效价研究

[目的]探讨高滴度制备犬瘟热病毒（CDV）的方法,对于提高该疫苗的保护率具有重要意义。[方法]选用FK81细胞,分别应用MEM和混合培养基（MEM和DMEM按9∶1的混合物）进行细胞培养和CDV接种,然后对2种培养基下的总细胞数、CDV的半数细胞感染量（TCID50）及电镜下病毒粒子的形态等进行了比较。[结果]混合培养基在总细胞数、TCID50及病毒粒子的形态方面均优于MEM培养基。同时还发现,在测定CDV的TCID50时,酶联免疫吸附试验（ELISA）法较细胞病变（CPE）法更灵敏。[结论]试验所建立的CDV增殖方法,可望用于犬瘟热疫苗的生产实践。     

Unmasking electronic energy transfer of conjugated polymers by suppression of O(2) quenching

The photochemistry of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV) has been found to be highly dependent on the presence of O(2), which increases singlet exciton quenching dramatically. Spectroscopy on isolated single molecules of MEH-PPV in polycarbonate films that exclude O(2) reveals two distinct polymer conformations with fluorescence maxima near 555 and 580 nanometers wavelength, respectively. Time-resolved single-molecule data demonstrate that the 580-nanometer conformation exhibits a "landscape" for intramolecular electronic energy relaxation with a "funnel" that contains a 580-nanometer singlet exciton trap at the bottom. The exciton traps can be converted to exciton quenchers by reaction with O(2). Conformationally induced, directed-energy transfer is arguably a critical dynamical process that is responsible for many of the distinctive photophysical properties of conjugated polymers.     

Metastable Rubidium Aluminum Silicate with a Hexagonal Sheet Structure

A compound of composition RbAlSi(3)O(8), with a structure of double sheets of silica-alumina tetrahedra with common apices held together by rubidium ions in 12-fold coordination, may be crystallized from a melt by rapid cooling. The compound is an analog of the metastable forms of the calcium, barium, strontium, and lead feldspars.     

X-ray Structure of the Cygnus Loop

X-ray emission from the Cygnus Loop was observed in the energy region around 0.2 to 1 kiloelectronvolt with a collector that focused x-rays along one dimension while scanning across the nebula. The total integrated intensity is 1.3x 10(-8) erg per square centimeter per second. The one-dimensional x-ray structure has the same angular size-about 3 degrees-as the outermost boundaries of the optical filaments. There is no increase in x-ray emission at the center of the nebula nor at the strong feature that is seen in certain radio maps. The x-ray spectrum is consistent with thermal radiation from a hot plasma at a temperature of about 4 x 10(6) degrees K with evidence for a line at 19 angstroms corresponding to the 2p-->1s transition of O VIII.     

微胚乳玉米子粒中蛋白质积累规律的分析

以高油115玉米作为对照,对微胚乳玉米胚和非胚部位中蛋白质的积累规律进行了分析。结果表明,这两类玉米胚部位中的单粒蛋白质重均呈直线增长趋势;在非胚部位,高油115玉米非胚单粒蛋白质重没有消减现象,微胚乳玉米非胚单粒蛋白质重在授粉后28 d达到峰值,之后下降,但其非胚蛋白质质量分数则有明显增长。收获时微胚乳玉米整粒子粒的蛋白质质量分数可达20%,为高油115的2倍左右。     

一氧化氮和过氧化氢诱导水稻细胞过敏反应的协同作用分析

 【目的】本文研究了信号分子一氧化氮(NO)和过氧化氢(H2O2)对水稻细胞过敏反应(HR)的诱导作用。【方法】用溴酚兰染色法定量检测这两种信号分子单独或协同诱导作用下水稻细胞的HR。【结果】该两种信号分子可以独立或协同诱导水稻细胞HR的产生，H2O2对NO诱导的HR具有调节作用，但NO与H2O2浓度平衡与否对HR诱导并无影响。【结论】H2O2和NO均是诱导水稻细胞HR的信号分子，诱导过程中并不存在"NO/H2O2 浓度平衡作用机制"。