Bithiazole metabolites from the myxobacterium Myxococcus fulvus

Two new bithiazole metabolites (3, 4) along with the previously reported compounds (1, 2) were isolated from the culture broth of the gliding bacterium Myxococcus fulvus collected from a Korean soil. The structures of these compounds were determined to be analogous to myxothiazole A on the basis of combined spectroscopic analyses. The new compounds exhibited significant cytotoxicity and moderate antifungal activity against the mouse fibloblast cell-line L929 and Candida albicans, respectively. These data were consistent with the previous finding that the bioactivity of myxothiazoles was highly dependent on the presence of terminal methoxy enol functionality.     

Group 12 metal complexes of [26]hexaphyrin(1.1.1.1.1.1)

Metalation of meso-hexakis(pentafluorophenyl)-substituted [26]hexaphyrin(1.1.1.1.1.1) (1) has been explored with group 12 metal ions Zn(II), Cd(II), and Hg(II). Zn(II) and Cd(II) ions afforded dinuclear gable-shaped complexes 2 and 3 in good yields, while Hg(II) ion provided bis-Hg(II) and mono-Hg(II) planar complexes (4 and 5) via C-H bond cleavage.     

Improved plasmalogen synthesis using organobarium intermediates

An improved synthesis of plasmalogen type lipids is described. Transmetalation of lithioalkoxy allyl intermediates with BaI(2) and subsequent alkylation with 1-iodoalkanes enables the stereoselective formation of O-(Z)-alkenyl ether as precursors for the synthesis of plasmenyl- and bisplasmenylcholines. This method provides a simple and adaptable approach for the stereocontrolled synthesis of plasmenyl derivatives with variations at the sn-1, sn-2, and sn-3 positions of the glycerol backbone.     

Synthesis of helicenes utilizing palladium-catalyzed double C-H arylation reaction

[5]- and [6]helicenes were synthesized in moderate to good yields from Z,Z-bis(bromostilbene)s by palladium-catalyzed double C-H arylation reaction. This method can be applied to the syntheses of helicenes possessing electron-deficient substituents.     

Properties of hybridized DNA arrays on single-crystalline undoped and boron-doped (100) diamonds studied by atomic force microscopy in electrolytes

Properties of hybridized deoxyribonucleic acid (DNA) arrays on single-crystalline undoped and boron-doped diamonds are studied at the microscopic level by atomic force microscopy (AFM) in buffered electrolytic solutions. DNA is linked to diamond via aminodecene molecules (TFAAD) that are attached to undoped diamonds by a photochemical reaction and via nitrophenyl-diazonium molecules attached electrochemically to boron-doped diamonds. Both H-terminated and oxidized diamond surfaces are used in this process. On H-terminated surfaces, AFM measurements detect compact DNA layers. By analyzing phase and height contrast in AFM, a DNA layer height of 76 A is determined on the photochemically functionalized diamonds and a DNA layer height of up to 92 A is determined on the electrochemically functionalized diamonds. Based on the layer thickness, the DNA chains are tilted under the angle of 31 degrees . The morphology of the DNA layers exhibits long-range (30-50 nm) undulations of 20 A in height and a nanoroughness of 8 A. Using Hertz's model for calculating the contact area of the AFM tip on a DNA layer and a geometrical model of DNA arrangement on diamond yields the DNA density on diamonds of 6 x 10(12) cm(-2) on both photochemically and electrochemically functionalized diamonds. The structure of these dense DNA layers is not significantly influenced by variations in buffer salinity of 1-300 mM NaCl. DNA molecules can be removed from the diamond surface by contact-mode AFM with forces >or= 45 nN and >or= 76 nN on photochemically and electrochemically functionalized diamonds, respectively, indicating that DNA is bonded covalently and stronger on diamond than on gold substrates. The DNA arrangement and bonding strength are similar on oxidized diamond surfaces when using an electrochemical process. On oxidized surfaces after photochemical processing, DNA is bonded noncovalently as deduced from the removal force < 6 nN. The presence of hybridized DNA as well as the selective removal of DNA by AFM scanning are corroborated by fluorescence microscopy.     

Preparation of a nanoporous CaCO3-coated TiO2 electrode and its application to a dye-sensitized solar cell

A nanoporous CaCO3 overlayer-coated TiO2 thick film was prepared by the topotactic thermal decomposition of Ca(OH)2, and its performance as an electrode of a dye-sensitized solar cell was investigated. As compared to bare TiO2, nanoporous CaCO3-coated TiO2 provided higher specific surface area and, subsequently, a larger amount of dye adsorption; this in turn increased short-circuit current (Jsc). Furthermore, the CaCO3 coating demonstrated increased impedance at the TiO2/dye/electrolyte interface and increased the lifetime of the photoelectrons, indicating the improved retardation of the back electron transfer, which increases Jsc, open-circuit voltage (Voc), and fill factor (ff). Thereby, the energy conversion efficiency (eta) of the solar cell improved from 7.8 to 9.7% (an improvement of 24.4%) as the nanoporous CaCO3 layer was coated onto TiO2 thick films.     

LaH分子的X1∑+态的势能函数

应用原子分析反应静力学原理导出ＬａＨ分子的电子状态和可能的离解极限,考虑相对论紧致有效势ＰＣＥＰ（Ｒｅｌａｔｉｖｉｓｔｉｃ Ｃｏｍｐａｃｔ Ｅｆｆｅｃｔｉｖｅ Ｐｏｔｅｎｔｉａｌ）近似下,用ＱＣＩＳＤ方法计算了ＬａＨ分子基态Ｘ＾１Σ＾＋的平衡几何Ｒｅ和离解能Ｄｅ为２．１２５Ａ和２．６２３ｅＶ,并在计算出来的一系列背地里点势能基础上,用正规方程组拟合Ｍｕｒｒｅｌｌ－Ｓｏｒｂｉｅ（Ｍ－Ｓ）势能函数,得     

Mo2C膜表面粗糙化规律的计算机模拟

引入晶粒边界修正,改进了Ｍｏ２Ｃ膜表面粗糙化物理模型,将ＤＴ２模型推广到包括有温度的情况对Ｍｏ２Ｃ膜表面形态进行计算机模拟并统计模拟图的高度分布,确定表面粗糙度随沉积时间和基底温度的变化规律,结果表明：引入晶粒边界修正大大促进了理论与实验结果的一致,Ｍｏ２Ｃ膜表面粗糙化属快速粗造化,粗造度随基底温度升高在而非线性地增大。     

3-巯基丙酸包裹的金纳米粒子自组装膜的制备及其层状周期性结构分析

制备了 3-巯基丙酸包裹的金钠米粒子水溶胶。在胺丙基三甲氧基硅烷覆盖的 Si或Si O2 基底上组装了上述金纳米粒子的单层膜和由 1 ,6-二巯基己烷联接的金纳米粒子多层膜。紫外 -可见吸收光谱和 X-射线衍射实验分析了多层膜的层状周期性结构     

Production of charged pions, kaons and antikaons in relativistic C + C and C + Au collisions

Production cross-sections of charged pions, kaons and antikaons have been measured in C+C and C+Au collisions at beam energies of 1.0 and 1.8 AGeV for different polar emission angles. The kaon and antikaon energy spectra can be described by Boltzmann distributions whereas the pion spectra exhibit an additional enhancement at low energies. The pion multiplicity per participating nucleon M(π⁺)/<A _part> is a factor of about 3 smaller in C+Au than in C+C collisions at 1.0 AGeV whereas it differs only little for the C and the Au target at a beam energy of 1.8 AGeV. The K⁺ multiplicities per participating nucleon M(K⁺)/ <A _part> are independent of the target size at 1 AGeV and at 1.8 AGeV. The K^- multiplicity per participating nucleon M(K^-)/ <A _part> is reduced by a factor of about 2 in C+Au as compared to C+C collisions at 1.8 AGeV. This effect might be caused by the absorption of antikaons in the heavy target nucleus. Transport model calculations underestimate the K^-/K⁺ ratio for C+C collisions at 1.8 AGeV by a factor of about 4 if in-medium modifications of K-mesons are neglected. Received: 10 December 1999 / Accepted: 14 November 2000