Initial excited-state structural dynamics of 2'-deoxyguanosine determined via UV resonance Raman spectroscopy

The resonance Raman spectra of 2'-deoxyguanosine, a DNA nucleoside, were measured in aqueous solution at wavelengths throughout its 260 nm absorption band. Self-consistent analysis of the resulting resonance Raman excitation profiles and absorption spectrum using a time-dependent wave packet formalism with two electronic states yielded the initial excited-state structural dynamics in both states. The vibrational modes containing the N(7)═C(8) stretching and C(8)-H bending internal coordinates were found to exhibit significant initial structural dynamics upon photoexcitation to either state and are coincident with the photochemical reaction coordinate involving the formation of the 2'-deoxyguanosine cation radical.     

Synthesis,X-ray analysis and photophysical properties of a new N-containing pentacyclic helicene

A new helically chiral pentacyclic system containing one pyrrole ring was prepared in a good yield and purity via a three-step sequence involving Heck coupling and classical oxidative photocyclization. X-ray crystal structure analysis indicated that the conformation resembled that of unsubstituted pentahelicene, the idealized symmetry of which is C₂. The optical properties of the pentacyclic helicene were investigated and show interesting behaviour.     

Effect of exchange of terminal substituents on the mesophase behaviour of some azo/ester compounds

Six homologous series of 4-(4′-alkoxy phenylazo) phenyl 4″-substituted benzoates (In_a-f) were prepared in which, within each homologous series, the length of the terminal alkoxy chain varies between 6, 8, 10, and 12 carbons, while the other terminal substituent, X, is a polar group that alternatively changed from CH₃O, CH₃, H, Br, NO₂ and CN. Compounds prepared were characterised by spectroscopic methods, and their mesophase behaviour investigated by differential scanning calorimetry (DSC) and polarised optical microscopy (POM). The results were discussed in terms of mesomeric and polarisability effects. In each group of compounds, bearing the same alkoxy substituent, the nematic-to-isotropic transition temperatures (T_C) were successfully correlated with the polarisability anisotropy of bonds to the substituent X. A comparative study was made between the investigated compounds and their previously prepared isomers, namely, 4-(4′-substituted phenylazo) phenyl 4″-alkoxybenzoates (IIn_a-f) in which the two terminal (alkoxy- and X) groups are exchanged.     

Effect of lateral substitution on supramolecular liquid crystal associates induced by hydrogen-bonding interactions between 4-(4′-pyridylazo-3-methylphenyl)-4′′-alkoxy benzoates and 4-substituted benzoic acids

Five laterally methyl-substituted pyridine-based derivatives of the title compounds (I 8–I 16), with molecular formula 4-C_nH_2n+1O-C₆H₄COOC₆H₃(3-CH₃)-N=N-C₅H₄N were prepared and their molecular formulae elucidated via elemental analyses, infrared, nuclear magnetic resonance and mass spectra. The number of carbon atoms in the alkoxy chain (n) varies between 8, 10, 12, 14, and 16 carbons. The newly prepared pyridine-based derivatives were investigated for their mesophase behaviour by differential scanning calorimetry and polarised optical microscopy; most of them were found to possess monotropic smectic C (SmC) mesophase. Two groups (A and B) of the 1:1 hydrogen-bonded associates, formed between each of the derivatives I 8– I 16 and two types of 4-substituted benzoic acids (II), were prepared and similarly characterised to investigate the effect of lateral methyl substitution on the central phenylene ring, as well as terminal polar substituents and alkoxy-chain length on the stability of the mesophases induced by intermolecular hydrogen bonding. In Group A complexes, mesomorphic 4-alkoxy benzoic acids, that carry the terminal n-alkoxy group of varying chain length, were used. The other series of complexes (Group B) is composed from the same pyridine-based derivatives and each of the non-mesomorphic 4-substituted benzoic acids that carries small compact polar groups, varying between CH₃O, CH₃, H, Cl, Br, and CN. All complexes prepared were investigated for their mesophase behaviour by differential scanning calorimetry and polarised optical microscopy and found to be purely smectogenic, possessing SmC as the only mesophase observed. The formation of the hydrogen-bonded complexes was confirmed by constructing their binary phase diagrams, which cover the whole range of concentration of the two complements.     

Purification, Sequencing, and Biochemical Characterization of a Novel Calcium-Independent α-Amylase AmyTVE from Thermoactinomyces vulgaris

α-Amylase from Thermoactinomyces vulgaris was highly purified 48.9-fold by ammonium sulfate precipitation, gel filtration on Sephadex G-50 column, and ion exchange chromatography column of DEAE-cellulose. The molecular weight of the enzyme was estimated to be 135 and 145 kDa by SDS–PAGE. Its high molecular weight is due to high glycosylation. The purified amylase exhibited maximal activity at pH 6.0 to 7.0 and was stable in the range of pH 4.0 to 9.0. The optimum temperature for its activity was 50 °C. The enzyme half-life time was 120 min at 50 °C, suggesting intermediate temperature stable α-amylase. The enzyme was sensitive to different metal ions, including NaCl, CoCl₂, and CaCl₂, and to different concentrations of EDTA. The enzyme activity was inhibited in the presence of 1 mM CaCl₂, suggesting that it is a calcium-independent α-amylase. The TLC showed that the amylase hydrolyzed starch to produce large maltooligosaccharides as the main products. A 1.1-kb DNA fragment of the putative α-amylase gene (amy TVE) from T. vulgaris was amplified by using two specific newly designed primers. Sequencing analysis showed 56.2 % similarity to other Thermoactinomyces α-amylases with two conserved active sites confirming its function.     

Y2O2S:Sm3+发光材料在不同激发波长的浓度特征

研究了在不同激发波长下三价钐离子掺杂硫氧化钇的发光强度对浓度的依赖关系。研究发现磷光体的发光强度不仅跟激活离子的浓度有关,而且跟激发时所采用的不同激发波长有关。磷光体发光强度与激活剂掺杂量的变化曲线表明,在不同激发路径下磷光体具有不同的发光性质。采用Sm^3 离子直接跃迁的413nm对样品进行激发时,发生猝灭的浓度低至约0．2mol％;当采用263nm高能紫外线激发时,浓度猝灭发生在较高浓度处(～2mol％),后者是前者的10倍。对Sm^3 离子发射强度与浓度关系曲线进行了拟合计算,结果表明Sm^3 在Y2O2S中浓度猝灭的原因主要是相邻中心的偶极-四极相互作用引起的交叉弛豫。     

H2-broadening,shifting and mixing coefficients of the doublets in the ν2 and ν4 bands of PH3 at room temperature

The broadening, shifting and mixing coefficients of the doublet spectral lines in the ν₂ and ν₄ bands of PH₃ perturbed by H₂ have been determined at room temperature. Indeed, the collisional spectroscopic parameters: intensities, line widths, line shifts and line mixing parameters, are all grouped together in the collisional relaxation matrix. To analyse the collisional process and physical effects on spectra of phosphine (PH₃), we have used the measurements carried out using a tunable diode-laser spectrometer in the ν₂ and ν₄ bands of PH₃ perturbed by hydrogen (H₂) at room temperature. The recorded spectra are fitted by the Voigt profile and the speed-dependent uncorrelated hard collision model of Rautian and Sobelman. These profiles are developed in the studies of isolated lines and are modified to account for the line mixing effects in the overlapping lines. The line widths, line shifts and line mixing parameters are given for six A₁ and A₂ doublet lines with quantum numbers K = 3n,?(n = 1,?2, …) and overlapped by collisional broadening at pressures of less than 50 mbar.     

可见光协同钴铈铁氧体高效活化过一硫酸盐降解噻虫胺

本实验采用溶胶-凝胶燃烧的方法,将Co掺入到CeFeO3（CFO）钙钛矿晶格中制备了具有晶格缺陷的CeFe0.8Co0.2O3（CFCO）纳米颗粒催化剂。通过扫描电镜（SEM）、透射电镜（TEM）、X射线衍射（XRD）、Ｘ射线光电子能谱（XPS）等表征技术对CFCO催化剂进行表征分析,结果表明在CFCO上形成了表面氧空位（VO）。同时,还研究了过硫酸氢钾（PMS）用量、不同pH值对CFCO降解噻虫胺（CTD）的影响。结果表明,在CFCO投加量为0.6 g?L-1,PMS用量为0.8 mmol?L-1,pH为7时,20 mg?L-1的噻虫胺在30分钟内完全降解。并且经过4次循环使用后,噻虫胺降解率仍能达到91.2%。CFCO对于PMS的高效活化能力,主要归功于晶格缺陷所产生的电位差促使自由电子顺着氧空位快速定向传导到PMS上。为了模拟在天然水体环境中CFCO光催化活化PMS去除CTD,进行阴离子和有机酸的对比实验,分析了不同环境因素对CFCO降解噻虫胺的影响;此外,本文通过自由基淬灭实验与电子自旋共振（ESR）检测确定了CFCO光催化活化PMS降解噻虫胺实验中起主要作用的活性物种为单线态氧（1O2）与羟基自由基（?OH）,并分析推测了自由基的产生机理。最后采用高效液相色谱-质谱联用仪（LC-MS）检测分析了CTD降解过程中可能产生的代谢产物,并基于代谢产物的产生顺序归纳出了三条可能的降解路径。     

Novel experimental design paradigm for development of eco-friendly gradient chromatographic method for simultaneous determination of metronidazole and spiramycin

This work describes the innovative experimental design-assisted development of a green gradient chromatographic method for concomitant analysis of metronidazole (MTR) and spiramycin (SPR). Two different designs including fractional factorial and Box-Behnken designs were implemented for screening and optimization steps, respectively. The optimum chromatographic conditions involved a mobile phase consisting of ethanol and 20 mM sodium dihydrogen phosphate solution (pH adjusted to 2.5) in the ratio 2:98 (v/v) for 2 min then the ratio changed to 30:70 (v/v). The flow rate was 1.3 mL/minute. Separation and analysis were performed on X-bridge C18 (150 mm × 4.6 mm × 3.5 μm) column with diode array detector set at 230 nm. Column oven temperature was 40°C. A linear response was acquired over the range of 5–125 μg/mL for both drugs. Detection and quantitation limits were 0.86 and 2.62 μg/mL for MTR and 0.92 and 2.83 μg/mL for SPR, respectively. The method was implemented for determination of both drugs in three tablet formulations. The method was proved to be green as evaluated by three assessment tools. The application of experimental designs assists in development of a robust green chromatographic method in gradient elution mode for determination of both drugs within reasonable time.     

Economic Electrochemical Sensors for the Determination of Eszopiclone in Pharmaceutical Formulation with Greenness Profile Assessment

Electrochemical-ion-selective-sensors offer green, rapid, economic and simple analytical-tool in pharmaceutical industry, control processes, physiological measurements and environmental monitoring. In this study, two sensors were introduced for eszopiclone (EZP) determination in pure-form and in pharmaceutical-dosage-forms using drug-ion-exchanger association complex fabrication technique. Two different ion-exchangers were used and compared, tetrakis (4-chlorophenyl) borate in sensor1 and tetraphenyl borate in sensor 2. Such sensors showed superior performance at pH 3.5 over a wide-range of EZP concentration. The proposed method was also assessed using GAPI and analytical Eco-scale. Low cost, short analysis-time, simplicity and greenness of the proposed sensors allow their use for high-through-put analysis in quality-control laboratories.