Dynamical properties of the soft sticky dipole-quadrupole-octupole water model: a molecular dynamics study

The dynamical properties of the soft sticky dipole-quadrupole-octupole (SSDQO) water model using SPC/E moments are calculated utilizing molecular dynamics simulations. This new potential for liquid water describes the water-water interactions by a Lennard-Jones term and a sticky potential, which is an approximate moment expansion with point dipole, quadrupole, and octupole moments, and reproduces radial distribution functions of pure liquid water using the moments of SPC/E [Ichiye and Tan, J. Chem. Phys. 124, 134504 (2006)]. The forces and torques of SSDQO water for the dipole-quadrupole, quadrupole-quadrupole, and dipole-octupole interactions are derived here. The simulations are carried out at 298 K in the microcanonical ensemble employing the Ewald method for the long-range dipole-dipole interactions. Here, various dynamical properties associated with translational and rotational motions of SSDQO water using the moments of SPC/E (SSDQO:SPC/E) water are compared with the results from SPC/E and also experiment. The self-diffusion coefficient of SSDQO:SPC/E water is found to be in excellent agreement with both SPC/E and experiment whereas the single particle orientational relaxation time for dipole vector is better than SPC/E water but it is somewhat smaller than experiment. The dielectric constant of SSDQO:SPC/E is essentially identical to SPC/E, and both are slightly lower than experiment. Also, molecular dynamics simulations of the SSDQO water model are found to be about twice as fast as three-site models such as SPC/E.     

锗分族元素二元团簇及其与Co形成的团簇离子

通过比较激光烧蚀E1/E2 (代表Ge/Sn， Ge/Pb和Sn/Pb) 和Co/E (E为Ge、Sn、Pb)混合样品形成的二元团簇负离子飞行时间质谱分布和谱峰的相对强度及形成的幻数团簇离子峰，发现E1/E2二元团簇离子中原子量大的锗分族元素在团簇离子中占主要组分，而原子量小的元素则少量掺杂，其组成和分布特点说明其结构和性质与纯E团簇离子相似，可能的结构为该类负离子团簇所有原子都在笼结构的骨架上；对于二元团簇离子GeSn9－、GePb9－和SnPb9－其结构可能是双帽反四棱柱构型，只是每个原子均为骨架的一部分.而对激光烧蚀过渡金属钴与锗分族元素的混合物的研究发现，反应形成了丰富的Co/E二元合金团簇负离子，分析发现该类簇离子为钴内包覆于E(锗分族元素)笼状结构.幻数离子CoGe10－、CoSn10－和CoPb10－可能具有双帽四角反棱柱结构，而CoPb12－可能具有二十面体构型，钴原子均为笼状结构的中心.     

HTPB／TDI,HDI聚合反应动力学研究

对端羟基聚丁二烯／甲苯二异氰酸酯，端羟基聚丁二烯／己二异氰酸酯甲苯溶液体系进行了反应动力学研究，用基团分析方法计算了相应体系的活化能，并对无催化剂和有催化剂的体系作了比较。结果表明，二丁基二月桂酸象对上述体系有强的催化作用，使体系的活化能降低，反应速度加快。对于对端差基聚丁二烯／甲苯二异氰酸酯体系，无催化剂时前后期反应活化能分别为２９．１ｋＪ／ｍｏｌ、３７．４ｋＪ／ｍｏｌ，有催化剂时前后期反应活化     

Syntheses and X-ray structures of mixed benzenethiolato-sulfido and -selenido trinuclear nickel clusters

The reaction between NiCl₂, NaSPh and NaEH (E = S, Se) in a mixture of acetonitrile and acetone gave trinuclear clusters [Ni₃(μ₃-E)(μ-SPh)₃(SPh)₃]²⁻(E = S, Se) and the previously characterized mononuclear complex [Ni(SPh)₄]²⁻. The X-ray structures of the trinuclear clusters are similar to each other except for the Ni₃E (E = S, Se) sections, and the Ni---E (E = S, E = S, Se) frameworks planes which are condensed via adjacent edges to form planar NiS₄ or NiS₃Se coordination planes which are condensed via adjacent edges to form cyclic systems with a triply bridging sulfido or selenido ion in the centre.     

Quantitative measurement of 17 beta-estradiol and estriol in river water by time-resolved fluoroimmunoassay.

A sensitive method for detecting 17 beta-estradiol (E2) and estriol (E3) in river water has been developed, based on the time-resolved fluoroimmunoassay by using a fluorescent europium chelate label, 4,4'-bis(1",1",1",2",2",3",3"-heptafluoro-4",6"-hexanedion-6"-yl)- chlorosulfo-o-terphenyl (BHHCT)-Eu3+. In the E2 assay, microtiter plates were coated with the E2-bovine serum albumin (BSA) conjugate. The anti-17 beta-estradiol antibody, the biotinylated goat anti-rabbit IgG antibody and the BHHCT-Eu3+ labeled streptavidin (SA)-BSA conjugate were used. In the E3 assay, the goat anti-rabbit IgG antibody was coated on a microtiter plate. The anti-estriol antibody and the BHHCT-Eu3+ labeled E3-BSA conjugate were used. The detection limits for E2 and E3 were 2.3 pg/ml and 4.3 pg/ml, respectively, and the analytical recoveries were 95-120%. Quantitative measurement of estrogens in river water was carried out for Kanda River (Tokyo, Japan) by using the method. The E2 and E3 levels were 32 pg/ml and 5.5 pg/ml, respectively. The detection limits of the present method are in the same orders of magnitude as those of ELISA for E2, and are 1-2 orders of magnitude better for E3.     

Endonuclease-based logic gates and sensors using magnetic force-amplified readout of DNA scission on cantilevers

The endonuclease scission of magnetic particles functionalized with sequence-specific DNAs, which are associated on cantilevers, is followed by the magnetic force-amplified readout of the reactions by the nano-mechanical deflection/retraction of the cantilevers. The systems are employed to develop AND or OR logic gates and to detect single base mismatch specificity of the endonucleases. The two endonucleases EcoRI (E(A)) and AscI (E(B)) are used as inputs. The removal of magnetic particles linked to the cantilever by the duplexes 1/1a and 2/2a via the simultaneous cleavage of the DNAs by E(A) and E(B) leads to the retraction of the magnetically deflected cantilever and to the establishment of the "AND" gate. The removal of the magnetic particles linked to the cantilevers by the duplex 3/3a by either E(A) or E(B) leads to the retraction of the magnetically deflected cantilever and to the establishment of the "OR" gate. The magnetic force-amplified readout of endonuclease activities is also employed to reveal single base mismatch specificity of the biocatalysts.     

Synthesis of isocyanide complexes of zinc. The molecular and crystal structure of Zn(SeC6H2Bu3)2(CNBu)2

The sterically hindered zinc chalcogenolato complexes [Zn(EAr″)₂]₂ (E = S, Se; Ar″ = 2,4,6-Bu^t₃C₆H₂) react with 1 equivalent of tert-butylisocyanide in non-coordinating solvents to give Zn(EC₆H₂Bu^t₃)₂(CNBu^t) (1, E = S; 2, E = Se) as thermally stable crystalline adducts; the compounds are thought to be chalcogenolato-bridged dimers. In the presence of excess isocyanide ligand the 1 : 2 adducts Zn(EAr″)₂(CNBu^t)₂ (3, E = S; 4, E = Se) are isolated. The compounds represent the first examples of well-characterized isocyanide complexes of zinc. The X-ray structure of 4 showed that it is monomeric with a distorted tetrahedral coordination geometry of the metal centre, which reflects the steric requirements of the chalcogenolato and isocyanide ligands, respectively.     

细胞色素b5突变体(E44A/E48A/E56A/D60A)的溶液结构研究

电子传递反应是光合作用和生物氧化等一系列重要生物过程的基本反应[1],为阐明细胞色素b5和c的静电结合模型,1993年Northrup等[3]用Brownian动态模拟预言的这两个蛋白结合模型有两种几何形态,根据以下模型设计了许多实验,但对两种模型都至关重要的细胞色素b5血红素暴霞棱周围的4个残基E44,48,56T D60对蛋白质复合物的稳定性以及在蛋白质识别中的作用仍然不清楚,为了阐明这4个带负电的残基对细胞色素b5结构的影响,正确地揭示蛋白质相互作用的本质和机理,本文对牛肝微粒体细胞色素b5胰蛋白酶切割后水溶性部分的突变体(E44A/E48A/E56A/D60A)深液结构进行了研究.     

Highly stereoselective synthesis of (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters and (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated amides from 1-bromo-1-fluoroalkenes via palladium-catalyzed carbonylation reactions

The highly stereoselective synthesis of (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated esters and (E)- and (Z)-alpha-fluoro-alpha,beta-unsaturated amides is described. 1-Bromo-1-fluoroalkenes (E/Z approximately 1:1), which are readily available starting materials, have been found to isomerize to high E/Z ratios after storage at -20 degrees C for 1 week or by photolysis at 254 nm. Since the (E)-isomers have been found to react faster than the corresponding (Z)-isomers at room temperature in Pd(0)-catalyzed reactions, the palladium-catalyzed carboalkoxylation of high E/Z 1-bromo-1-fluoroalkenes lead to a high Z/E (Z/E >/= 98:2) ratio of the alpha-fluoro-alpha,beta-unsaturated esters. When 1-bromo-1-fluoroalkenes (E/Z approximately 1:1) were reacted with HCOOH/NBu(3)/Pd(II)/DMF, the (E)-isomer was selectively reduced, and the remaining (Z)-1-bromo-1-fluoroalkenes were recovered in essentially pure isomeric form. The resulting mixture of (Z)-1-bromo-1-fluoroalkenes and the reduced products underwent similar palladium-catalyzed carboalkoxylation reactions at 70 degrees C, and the (E)-alpha-fluoro-alpha,beta-unsaturated esters were stereospecifically obtained. This methodology was also successfully applied for the stereospecific synthesis of (Z)- and (E)-alpha-fluoro-alpha,beta-unsaturated amides: the palladium-catalyzed carboamidation reaction of high E/Z and (Z)-1-bromo-1-fluoroalkenes lead to pure (Z)- and (E)-alpha-fluoro-alpha,beta-unsaturated amides, respectively.     

Structure of mixed anionic/nonionic surfactant micelles: experimental observations relating to the role of headgroup electrostatic and steric effects and the effects of added electrolyte

The structures of the mixed anionic/nonionic surfactant micelles of SDS/C12E6 and SDS/C12E8 have been measured by small angle neutron scattering (SANS). The variations in the micelle aggregation number and surface charge with composition, measured in D2O and in dilute electrolyte, 0.01 and 0.05 M NaCl, provide data on the relative roles of the surfactant headgroup steric and electrostatic interactions and their contributions to the free energy of micellization. For the SDS/C12E8 mixture, solutions increasingly rich in C12E8 show a modest micellar growth and an increase in the surface charge. The changes with increasing electrolyte concentration are similarly modest. In contrast, for the SDS/C12E6 mixture, solutions rich in C12E6 show a more significant increase in aggregation number. Furthermore, electrolyte has a more substantial effect on the aggregation for the nonionic (C12E6) rich mixtures. The experimental results are discussed in the context of estimates of the steric and electrostatic contributions to the free energy of micellization, calculated from the molecular thermodynamic approach. The variation in micelle surface charge is discussed in the context of the "dressed micelle" theory for micelle ionization, and other related data.