CHEMIEXCITATION IN THE PEROXIDATIVE METABOLISM OF N- METHYLCARBAZOLE: MECHANISTIC IMPLICATIONS

Abstract –The peroxidative metabolism of TV-methylcarbazole emits light independently of the presence of oxygen. It is likely that two chemiexcited transients are formed by electron transfer to the activated peroxidase, the cation radical by one electron transfer and a cation biradical by two electron transfer consistent with the failure to observe horseradish peroxidase-II in the steady state of the reaction. In the spectral range investigated (390–700 nm) the observed emission (570–700 nm) is ascribed to the biradical, as the latter is equivalent to an excited state of the postulated iminium cation.
While lipoxygenase has no effect upon JV-methylcarbazole, it markedly enhances the emission if peroxidase is present. This effect requires oxygen and is ascribed to an excited product formed by lipoxygenase acting upon an intermediate hydroperoxide of the aerobic process promoted by peroxidase.     

对四-2,3-吡啶并紫菜嗪铬的薄膜电极的光电化学研究

Photocurrent spectra and photoluminescence measurements of the electrode covered by a thin film of chromium tetra-2,3-pyridinoporphyrazine by conventional 3-electrode system method have been performed. The cathodic photocurrent has been measured. The shape of the photocurrent spectrum is similar to that of photoluminescence spectrum. Their intensities change as a function of the applied potential. Two photoluminescence peaks are located at about 470 nm and 520 nm. The results indicate that the thin film behaves like a p-type semiconductor with a band gap width of about 2 eV.     

EXCITATION OF CHLOROPLASTS IN Euglena gracilis IN THE ABSENCE OF LIGHT

Abstract— Challenging Euglena gracilis —a unicellular microorganism that contains chloroplasts—with phenylacetaldehyde induces malondialdehyde formation, sustained red emission and Hill activity. In chloroplasts, phenylacetaldehyde appears to undergo peroxidase catalyzed oxidation to formic acid and triplet benzaldehyde; the latter or, less likely, a precursor thereof promotes lipid peroxidation. Triplet benzaldehyde and/or the excited species formed in lipid peroxidation transfer energy to the chlorophylls. This explanation also applies to spinach chloroplasts preparations, thus accounting for the previous unexplained observation that phenylacetaldehyde induced sustained red emission and Hill activity. A homogeneous picture is now available regarding the intracellular generation of excited states and concomitant excitation of built-in structures.     

Ab initio study of possible intermediates in the no(4Π) catalyzed geometric isomerizations of olefins

The geometries of acyclic and three-membered ring (nitroxide) H₄C₂NO radicals in their ground ²Π electronic states have been optimized completely at ab initio UHF and ROHF theoretical levels with the STO-3G and the 6-31G** basis sets. The optimizations favour the cyclic nitroxide structure energetically. However ΔE(acyclic - cyclic) at the UHF and ROHF/6-31G** levels are only 3.2 and 1.9 kcal mol^-1, respectively. Incomplete MP2/6-311G** optimizations support these results. The zero-point energy computed at the ROHF/6-31G** level for the nitroxide radical is 2.5 kcal mol^-1 higher than that for the acyclic structure, thus reversing the relative energies by 0.6 kcal mol^-1. The energies of the two radical structures, relative to the sum of those for ethylene and NO, are very close to literature values of the activation energies for the thermal, NO catalyzed geometrical isomerizations of olefins. Thus cyclic nitroxide intermediates may play a role not only in the Hg 6(³P₁) photosensitized, but also in the thermal, NO-catalyzed geometric isomerizations of olefins. Paper dedicated to Professor Otto P. Strausz; presented in part at the 75th Canadian Chemical Congress and Exhibition, Edmonton, May 31 – June 4, 1992.     

钒氧酞菁薄膜瞬态光电压性能的研究

本文分别用1064nm, 532nm和 355nm激发波长的YAG脉冲激光对所制备的phase Ⅱ结构钒氧酞菁膜Al\phase ⅡVOPc\ITO夹心电池进行瞬态光电压响应研究.随着3种波长激发光脉冲强度的增加, 瞬态光电压信号均增强. 激发光波长1064nm、532nm处于酞菁膜Q-带吸收区肩部, 光电压的极性与激发光入射方向无关, 均为负信号; 而激发光波长 355nm处于酞菁膜B-带, 光电压的极性与激发光入射方向有关, 从ITO极方向激发产生正电压信号, 从A1极激发产生负电压信号. 激发光波长对夹心电池的光电压产生有明显的作用, 光电压产生过程中应存在不同的机理. 这与前文^[1]对同一夹心电池稳态光电压响应研究所推断的结论一致.     

ChemInform Abstract: XeNO3+: A Gaseous Cation Characterized by a Remarkably Strong Xe—O Bond.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.     

DELPHI有机共轭体系MM力场的优化和应用

运用我们建议的SC-HMO方法优化了有机共轭烯烃的DELPHIMM力场。将优化所得力场和参数用于计算各类型101个共轭化合物的分子几何构型、生成热、偶极矩和IR频率等, 结果可与MM3法相比。     

Yb3+/Er3+共掺(MLaFn)x(M=0,K;n=3,4;x=1,1.5)纳米材料的控制合成及其上转换发光性质

采用水热与溶剂热结合的方法,在乙二醇-正己醇体系中,通过调节KF与RE(RE=La,Yb,Er)的量比、反应温度和反应时间实现了由LaF_3(六角相)到KLaF_4(立方相、六角相)晶型的控制合成。借助透射电子显微镜(TEM)和X射线粉末衍射(XRD)对样品的结构和微观形貌进行表征。结果表明,当KF/RE比例为2. 25时,制备的样品为片状的六角相LaF_3纳米颗粒;当KF/RE比例为3. 00时,得到具有近似球形的立方相KLaF_4纳米颗粒;当KF/RE比例为4. 25时,得到了六角相(KLaF_4)_(1. 5)纳米颗粒。上转换发射光谱显示:所有的样品在近红外光(980 nm)激发下,均有3个明显的发射峰,在522 nm、544 nm处分别对应于Er~(3+)的~4S_(3/2),~2H_(11/2)→~4I_(15/2)能级跃迁,655 nm处属于Er~(3+)的~4F_(9/2)→~4I_(15/2)能级跃迁。     

西藏拉萨市周边温棚蔬菜样品中农药残留量的研究

用农药残毒速测仪和气相色谱 火焰光度检测器（GC FPD）2种方法对拉萨市周边4个温室蔬菜基地抽样采集的26个蔬菜样品测定其农药残留量.结果,用速测仪检测出7个蔬菜样品中有农药残留存在.为进一步验证其结果,参考国家农业标准NY/T 761-2008,建立了气相色谱火焰光度(GC-FPD)检测蔬菜样品中敌敌畏、氧化乐果、二嗪农、乐果、甲基对硫磷、马拉硫磷、对硫磷、水胺硫磷、喹硫磷9种有机磷农药残留的分析方法,建立的气相色谱分析方法：检出限为0.039 7～0.182 0 μg·mL^-1、回收率为51.64%～91.04%、方法的精密度为1.61%～10.80%.用该方法对农药残留超标的蔬菜样品进行分析,结果未检测到上述9种有机磷农药的残留.实验结果为从事农药残留检测工作者在分析方法的选择和评价拉萨市蔬菜农药残留状况提供参考.     

Simulation of vapour-liquid equilibria for branched alkanes

A new united-atom force field is proposed for branched and linear alkanes. The proposed force field is used to study vapour-liquid equilibria for pure components and binary mixtures. Results of phase equilibria simulations are found to be in good agreement with available experimental data.