Direct and sensitized photoprocesses of bis-benzimidazole dyes and the effects of surfactants and DNA

The photoprocesses of two bis-benzimidazole dyes, Hoechst 33258 (1) and an analog, where the phenolic group in p-position is replaced by an ethoxy group, Hoechst 33342 (2), were studied. For 1 and 2 in aqueous solution the quantum yield of fluorescence is strongly pH dependent; it decreases from a maximum value of phi f = 0.4 at pH 5 to phi f = 0.02 at pH 8. The effects of absorption and fluorescence, induced by sodium dodecyl sulfate surfactants below and above the critical micelle concentration and by double-stranded DNA, are interpreted by assuming that in bulk aqueous solution the dyes are essentially present as monomers. The strong enhancement of phi f, when the dye is bound to double-stranded DNA or solubilized in micelles, is suggested to be due to different environments at the benzimidazole rings. A quinoid intermediate with absorption maximum at 380 nm is formed for 1 at neutral pH using lambda exc = 248 or 308 nm. N-centered radicals of 1 or 2 in aqueous solution were observed by laser flash photolysis after electron ejection using wavelengths of 193 or 248 nm (mono and biphotonic, respectively). The precursor radical cation escaped observation but is transformed into the above radicals by deprotonation. Electron transfer from 1 in aqueous solution to triplet acetone takes place, and subsequent deprotonation is proposed to yield N-centered radicals. In addition, energy transfer from acetone to 1 is suggested, leading to T-T absorption with the maximum at 700 nm. The photoprocesses are discussed and the results compared with those known from pulse radiolysis.     

Synthesis and characterization of copolyesters of PET and substituted p-hydroxybenzoic acids

Random copolyesters of different compositions were synthesized by melt polycondensation of poly(ethylene terephthalate) and 3-bromo - and 3,5-dibromo-p-hydroxybenzoic acids. The copolymer compositions were determined by proton nuclear magnetic resonance spectroscopy. The thermal behavior of these copolyesters was investigated by differential scanning calorimetry. The glass transition temperature, crystallization temperature, and decomposition temperature were found to increase with increase in the paraoxybenzoate content of the copolyesters. The limiting viscosity number and the weight-average molecular weight were determined.     

Synthesis and characterization of amphiphilic star copolymer of beta-cyclodextrin and polypropylene oxide and their application as nanocarriers

The present study was aimed at synthesizing and characterizing star copolymers of ??-cyclodextrin and exploring their application as nanocarriers. The copolymers of ??-cyclodextrin and polypropylene oxide were synthesized by using ring opening polymerization, catalyzed by base, under high temperature and pressure. The polymers of different molecular weight were synthesized by increasing chain length of polypropylene oxide at optimized temperature, pressure and concentration of catalyst. The structure of synthesized polymer was confirmed by IR and NMR. Molecular weight and molecular weight distribution was evaluated by hydroxyl number and gel permeation chromatography respectively. Amphiphilic nature of the polymers was evaluated by determining the solubility in water and different organic solvents. For the evaluation of polymer as a nanocarrier, Ibuprofen was selected as model drug. Loading efficiency and release of Ibuprofen from the complex were also investigated. It was observed that, with increase in the molecular weight of the polymers, loading capacity was increased.     

Ozonolysis and combination of ozonolysis and radiolysis of aqueous fluorene

The degradation of fluorene, a toxic and carcinogenic substance formed by combustion of fossil fuels, was studied in alkaline, aqueous solution. It is very efficiently decomposed by ozonation, where 9-fluorenone and 9-fluorene carboxylic acid appear as major products in addition to a mixture of aldehydes and carboxylic acids. A more efficient substrate decomposition was observed by a treatment with γ-rays in the presence of ozone. The yield of the main products was in the case 4-times lower compared to those obtained by ozonation only. Some probable reaction steps are presented for explanation of the products.     

Vibrational dynamics and stability of the high-pressure chain and ring phases in S and Se

The high-pressure phases of group-VI elements sulfur and selenium in their spiral chain and ring structures are examined by in situ Raman and x-ray diffraction techniques combined with first principles electronic structure calculations. The S-II, S-III, Se-I, and Se-VII having spiral chain structures and S-VI with a molecular six-member ring structure are studied in a wide P-T range. The square spiral chain structure of S-III and Se-VII is characterized by seven Raman modes that harden with increasing pressure. The calculations reproduce the observed frequencies and allow the authors to make the mode assignment. The "p-S" and "hplt" phases of sulfur reported by previous Raman studies are identified as S-II and S-III with the triangular and square spiral chain structures, respectively. The phase relations obtained by the x-ray and Raman measurements show that the high-pressure high-temperature phases of sulfur, observed by x-ray, can be induced by laser illumination at room temperature.     

系列甘露糖醛酸寡糖的制备与鉴定

用酸降解法制备了系列甘露糖醛酸寡糖(聚合度2～8),并分析测定了寡糖的结构. 褐藻胶经部分酸水解,于pH=2.85处分级获得聚甘露糖醛酸. 继续用酸降解法降解聚甘露糖醛酸,经凝胶柱层析分离纯化,获得系列甘露糖醛酸寡糖. 用荧光标记糖电泳(FACE)对寡糖进行了分析,并用电喷雾离子化质谱(ESI-MS)、 核磁共振波谱(NMR)及红外光谱(FTIR)进行了结构表征. 本研究用酸降解法制备饱和甘露糖醛酸寡糖,用凝胶柱层析法分离获得系列聚合度的寡糖,为褐藻胶大分子构效关系研究和药物的筛选与发现提供了重要的基础资料.     

三氯环硼氮烷和聚硼氮烷的合成与表征

以三氯化硼和氯化铵为原料,甲苯为溶剂,高产率(98%)地合成了具有硼和氮的六元环结构的三氯环硼氮烷(1);1分别与正丙胺(Ⅰ)和异丙胺(Ⅱ)反应制得正丙胺基环硼氮烷(1~Ⅰ)和异丙胺基环硼氮烷(1~Ⅱ);1~Ⅰ和1~Ⅱ经过脱胺和热聚合反应制得聚硼氮烷先驱体(2和3).用IR,NMR和XRD等对2和3的组成与结构进行了分析,探讨了聚硼氮烷的胺基取代基对聚硼氮烷聚合反应性及产物结构的影响.研究结果表明,3具有更强的热聚合特性.     

Simultaneous spectrophotometric determination of molybdenum and selenium,and of molybdenum and tellurium

A method is reported for the extraction of molybdenum-phenylfluorone by chloroform. The extraction is complete whether perchlorate ions are present or not but the extractions in the presence of perchlorate ions gave a somewhat more sensitive procedure for the spectrophotometric determination of molybdenum in the solvent phase as the molybdenum-phenylfluorone complex.A procedure is reported for the simultaneous determination of molybdenum and selenium, and molybdenum and tellurium. The method involves first the formation and solvent extraction of the molybdenum-phenylfluorone complex by chloroform in the presence of perchlorate ions, followed by determination of selenium in the remaining aqueous phase as selenium-diethyldithiocarbamate complex after solvent extraction with 2-ethyl-1-hexanol in the presence of perchlorate ions. A similar procedure is reported for the simultaneous determination of molybdenum and tellurium except that in the determination of molybdenum, the phenylfluorone complex is extracted by chloroform in the absence of perchlorate ions. Tellurium is determined in the remaining aqueous phase as tellurium-diethyldithiocarbamate complex after solvent extraction by 2-ethyl-1-hexanol solvent extraction in the presence of perchlorate ions.     

Synthesis of pyrazolo-enaminones,bipyrazoles and pyrazolopyrimidines and evaluation of antioxidant and antimicrobial properties

A novel pyrazolo-enaminones, bipyrazoles and bipyrazolopyridines from 1-(5-hydroxy-3-methyl-1-phenyl-1H-pyrazol-4-yl)butane-1,3-dione and 4-methyl-2-phenyl-2H-pyrazolo[3,4-b]pyridine-3,6(3aH,7H)-dione have been synthesized by assisted heating with microwave radiation without any catalyst. The pyridine and pyrazole ring formation has been developed from easily accessible enamino keto esters by formylation followed by intramolecular cyclization. The general applicability for the synthesis of the important pyrazolo-enaminones, bipyrazoles and pyrazolo-pyridines heterocycles was attributed to simplicity of operation, synthesis without catalyst, energy efficiency (shorter reaction time under microwave irradiation), good yields, more environmentally friendly and more cost-effective procedure. The antioxidant activity of new heterocyclic compounds was evaluated by free radical scavenging by DPPH assay. Several of these compounds showed good activity against both Gram-positive (S. aureus) and Gram-negative (E. coli) bacteria.     

Physical and Chemical Properties of Magnetite and Magnetite-Polymer Nanoparticles and Their Colloidal Dispersions

The properties of polymer-coated magnetite nanoparticles, which have the potential to be used as effective magnetic resonance contrast agents, have been studied. The magnetite particles were synthesized by using continuous synthesis in an aqueous solution. The polymer-coated magnetite nanoparticles were synthesized by seed precipitation polymerization of methacrylic acid and hydroxyethyl methacrylate in the presence of the magnetite nanoparticles. The particle size was measured by laser light scattering. It was shown that the particle size, variance, magnetic properties, and stability of aqueous magnetite colloidal dispersion strictly depend on the nature of the stabilizing agent. The average hydrodynamic radius of the magnetite particles was found to be 5.7 nm in the stable aqueous colloidal dispersion. An inclusion of the magnetite particle into a hydrophilic polymeric shell increases the stability of the dispersion and decreases the influence of the stabilizing agent on the magnetic and structural properties of the magnetite particles as was shown by X-ray diffraction and M?ssbauer and IR spectroscopy, as well as by vibrating sample magnetometry. The variation in the polymeric shell size and the polymer net density can be useful tools for evaluation of the polymer-coated magnetite particles as effective contrast agents. Copyright 1999 Academic Press.     

甲壳胺-g-PEG的合成及医用性能的研究(Ⅰ)甲壳胺-g-PEG的合成及表征

通过官能团偶联反应，将端基改性为醛基的甲氧基聚乙二醇（分子量分别为２０００、５０００），按不同配比与甲壳胺反应，制得了甲壳胺接枝ＰＥＧ的产物（Ｃｈｉｔｏｓａｎ－ｇ－ＰＥＧ）。讨论了反应的最佳ｐＨ条件。建立了有效的产物分离方法，用红外光谱法、１Ｈ－ＮＭＲ法对产物的本体结构进行了表征，并用元素分析法和１Ｈ－ＮＭＲ法对接枝量进行了测定。     

固相法合成苯胺与邻甲氧基苯胺共聚物及其性能

以苯胺和邻甲氧基苯胺为单体,甲磺酸为掺杂酸,用固相法合成了甲磺酸掺杂苯胺与邻甲氧基苯胺共聚物。 通过红外光谱、紫外可见吸收光谱、X射线衍射、透射电子显微镜、循环伏安和电导率等对共聚物进行了结构表征和性能测试。 结果表明,不同摩尔比的苯胺与邻甲氧基苯胺共聚物处于中间氧化态,随邻甲氧基苯胺含量的增大,共聚物的掺杂率降低。 共聚物具有较高的结晶性和纤维状形貌,当苯胺与邻甲氧基苯胺摩尔比为1∶1时,具有较高的电化学活性,其导电率为1.65 S/cm。     

元素分析仪测定土壤、沉积物样品碳氮含量的影响因素及数据校正

使用元素分析仪进行土壤、沉积物样品碳、氮含量检测时,样品前处理过程(烘干和酸化)、包样质量以及参考标准品等因素均会对检测结果造成影响.试验结果表明:酸化导致氮百分质量的测定结果降低2.6%~40.0%,碳百分质量的测定受包样质量的影响较大,使用的校正标准与被测样品越相似,校正结果越准确.     

HPLC separation and fluorimetric estimation of chlorophylls and pheophytins in fresh and frozen peas

Summary A HPLC method for the separation and estimation of chlorophylls and pheophytins in fresh and frozen peas was assessed with the aim of following the colour changes of the products during storage under frozen conditions.The method involves the acetone extraction of the pigments, followed by HPLC on RP18 with isocratic elution by acetone: ethanol:water, (70:17:13), detecting and estimating the separated compounds by fluorimetry. The mobile phase composition was selected by monitoring the separation efficiency of several mixtures of solvents by HPLC. The reliability and the accuracy of the method were checked.     

Preparation and characterization of thin films of monomeric and polymeric octacyanophthalocyanines

Thin films were prepared on substrates, cleavage surface of KCl single crystal, and metallic copper, by reaction of 1,2,4,5-tetracyanobenzene with the substrate at various temperatures. The films were characterized by elemental analysis, IR, and UV/VIS spectroscopies. The films were observed by scanning electron microscopy. The films produced on copper at temperatures between 300 and 400°C consisted of copper octacyanophthalocyanine and its polymer with ladder structure. The ratio of polymer to monomer increased with elevating the reaction temperature. The films were composed of ribbon-like crystals. The film produced on copper above 450°C was composed of an amorphous and continuous layer of polymeric copper phthalocyanine. The film produced on KCl at temperatures between 250 and 350°C consisted of potassium octacyanophthalocyanine and its polymer with ladder structure. The film produced on KCl above 450°C was polymeric potassium phthalocyanine. Those films contained more metal content than that required stoichiometrical.     

Stereodynamics and conformational chirality of the atropisomers of ditolyl anthrones and anthraquinone

Syn and anti conformers in similar proportions were observed at ambient temperature for the title compounds. The conformational assignment of the two anthrones was obtained by the observation of different multiplicity of the methylene NMR signals, whereas that of the anthraquinone derivative was determined by NOE experiments. The anti-to-syn interconversion barriers were obtained by line-shape simulation of the temperature-dependent NMR spectra, and by saturation transfer experiments. In one case the X-ray diffraction indicated that the syn is the only structure observed in the crystals.     

Determination and differentiation of nitrilotriacetic acid and ethylenediaminetetra-acetic acid

Ethylenediaminetetra-acetic acid (EDTA) and nitrilotri-acetic acid (NTA) can be differentiated and determined by titration with metal ions to visual metallochromic dye end-points. EDTA can be determined without interference from NTA, either by titrating with copper(II) at pH 5 using PAN indicator, or by titrating with iron(III) at pH 6 and 70 degrees using Tiron indicator. The total chelating power (EDTA + NTA) can be determined either by titrating with lead(II) at pH 4.4 using dithizone indicator, or by titrating with iron(III) at pH 3.5 using Tiron indicator ; NTA is determined by difference. The lowest concentration at which NTA can be determined in EDTA by titration to the iron(III)-Tiron end-point is about 1 wt.%. The apparent stability constants of the iron(III)-Tiron complexes under the conditions of the titration at pH 3.5 and pH 6 have been determined using the method of continuous variations.     

Synthesis and characterization of biocompatible and biodegradable polymers

New polyesters were synthesized using Krebs cycle acids. Poly(1, 4-butanediol dilactate succinate)(PBDS) and poly(1, 4-butanediol dilactate 2-acetoxy succinate)(PBDAS) were prepared by the polycondensation of 1, 4-butanediol dilactate with succinic anhydride and 2-acetoxy succinic acid, respectively. Poly(1, 4-butanediol succinate)(PBS) was also synthesized from 1, 4-butanediol and succinic anhydride. PBS/PBDS and PBS/PBDAS blends were prepared by the method of solvent casting. The effects of crystallization time and temperature onto melting behavior of PBS/PBDS and PBS/PBDAS blends were investigated by differential scanning calorimetry. The compatibility of each blend system was discussed using equilibrium melting point depressions. The biodegradation behavior was studied using PBS, PBDS, and PBDAS as the sole carbon source by Aspergillus niger. The molecular weights of the polymers which were obtained from GPC analysis decreased after degradation in five weeks.     

Preparation and properties of lanthanum tungstate and studies of its ion-exchange and electrochemical behaviour

A new inorganic ion-exchanger lanthanum tungstate has been prepared by mixing lanthanum nitrate and sodium tungstate. The refluxed product has been found to be most suitable; therefore, most of the electrochemical and ion-exchange studies were performed on this product. The material is a weak cation exchanger with a capacity of 0.80 mmol per gram. Electrochemical studies are performed by preparing a pellet of this exchanger in polystyrene; charge density and membrane potential have been calculated. The results are discussed.     

Synthesis of colloids and films of Pr, Er and Yb with nonaqueous solvents

Colloidal dispersions of Yb, Er and Pr have been prepared by chemical liquid deposition. The metals were cocondensed at 77 K with 2-methoxyethanol and ethanol to produce solvated metal atoms. The particle size of the dispersions was determined by transmission electron microscopy to range from 52 to 1080 Å; the particles had spherical shapes. After solvent evaporation under vacuum, active solids and amorphous powder were deposited over Cu and Al metal. Dispersion stability, particle size, UV/Vis absorption and zeta potential were studied. The solids prepared by solvent evaporation were characterized by Fourier transform infrared (FTIR) spectroscopy and thermogravimetric analysis (TGA). The films prepared on Al were studied by scanning electron microscopy. The most stable colloid was obtained using 2-methoxyethanol: several concentrations were stable for several months and the zeta potential indicated that this colloid stability is mainly due to solvation effects. FTIR spectroscopy of the solids indicated solvent incorporation in the film. This observation was corroborated by thermal analysis. Information on the thermal stability of the films was obtained by TGA. The UV/Vis absorption spectrum was measured at several concentrations under different conditions.