FREE RADICALS FROM PHOTOREDUCTION OF HEMATOPORPHYRIN IN AQUEOUS SOLUTION

—The anaerobic photoreduction of hematoporphyrin by organic reducing agents in fluid aqueous solutions has been studied by electron spin resonance spectroscopy. Efficient photoreduction occurs with many hydrogen-atom or electron donors, including catechols, pyrogallol. hydroquinone. ascorbate, p -phenylenediamine, cysteine and glutathione. A combination of direct and spin-trapping measurements (using 2-methyl-2-nitrosopropane) has been used to confirm production of radicals from both the porphyrin and the reducing agent in each system.     

离子色谱法测定乙二胺水溶液中的SO32-、SO42-

用离子色谱法测定5％乙二胺水溶液中的SO3^2-、SO4^2-。选用IonPac柱，以3mmol/L AS11分离碳酸钠－10％甲醇水溶液作为淋洗液，20min内便可完成测定。SO3^2-和SO4^2-的回收率分别为97.6%-101.6%和99.2%-101.0%，相对标准偏差分别为1．31％和1．42％。     

LUMINESCENCE AND PHOTOCHEMISTRY OF 4-THIOURIDINE IN AQUEOUS SOLUTION

Abstract— In bidistilled water, 4-thiouridine (4TU) exhibits a weak unusual luminescence, the quantum yield of which is 3 × 10^-4 at 25°C. The excitation spectrum corresponds well to the 4TU absorption spectrum. The emission lies at longer wavelengths (Λ_max 550 nm) than the 4TU phosphorescence observed at 77 K (Λ_max, 470–480 nm). From the emission signal obtained after an excitation flash of 3 ns half-width, an "apparent" rate constant for the radiative deactivation process, shorter than 5 × 10⁶ s, can be inferred. The 300 K emission is efficiently quenched by halides and by oxygen: quenching involves a long-lived intermediate (⋍ 200 ns).
Clearly the emissive state X is populated through the S₀-S₁ electronic transition π→π* of 4TU. The nature of X cannot be unambiguously determined: it cannot be an excimer but can be either the 4TU triplet state or another chemical state distinct from the 4TU excited singlet or triplet states.
An interesting finding is that the 300 K emission and the ability of 4TU to photoreact are related: they are quenched with the same efficiency by halide anions. This indicates that quenching occurs at the same long-lived intermediate species , which is either a precursor of the emitter or the emitter itself.     

水溶液中混合金属离子与胆固醇的相互作用

微量元素与影响人类健康的某些疾病关系极大。高胆固醇血症是动脉粥样硬化 (ＡＳ)的致病原因[1] ,而Ｃｕ、Ｚｎ、Ｃｄ、Ｃｒ等元素与高胆固醇血症紧密相关。实验研究发现缺铜动物体内胆固醇浓度增高。动物实验也发现铜缺乏诱发ＡＳ ,有实验表明[2 ] :红细胞内铜与胆固醇及冠脉病变呈负相关 ,提示血中铜缺乏可能是形成冠状动脉狭窄的危险因素 ;铜缺乏使肌体胆酸的合成和排泄减少 ,胆固醇从肝脏到血浆的转移增加或使肝细胞对循环胆固醇的额外利用减少 ,从而导致高胆固醇血症。在ＡＳ中 ,高锌是另一个重要因素[3 ] ,高锌不但直接降低血浆高密度…     

邻-氨基酚修饰吸附树脂对2-氨基吡啶的静态吸附热力学及动力学特征

合成了两种邻-氨基酚修饰超高交联吸附树脂(MOAR-1、MOAR-2),并用该树脂对水溶液中2-氨基吡啶的静态吸附热力学和动力学特征进行研究。热力学研究结果表明,Freundlich吸附等温方程能够对静态吸附等温线进行很好地拟合。吸附焓变ΔH<0,其绝对值小于60kJ/mol,表明以物理吸附为主以及该吸附剂容易脱附的特征;ΔG<0,说明吸附是自发行为;ΔS<0,表明吸附质分子在树脂表面上的运动受到了限制。两种树脂对2-氨基吡啶的吸附量随着温度的升高而降低,适当降低温度有利于吸附。动力学研究的结果表明:吸附符合一级动力学方程,吸附速率随温度升高而增大。表观活化能Ea<4.0kJ/mol,说明吸附较容易进行。     

水溶液中Cu^2＋,Zn^2＋双组分金属离子与胆固醇的相互作用

水溶液中Ｃｕ２＋、Ｚｎ２＋双组分金属离子与胆固醇的相互作用宋仲容（重庆高等师范专科学校化学系永川４０２１６８）李树伟（四川师范大学化学系成都６１００６６）关键词Ｃｕ２＋Ｚｎ２＋胆固醇吸附中国分类号Ｏ６１１．３铜锌金属离子在冠心病的发生与发展中有着重要...     

THE PHOTOCHEMISTRY OF 5-METHYLCYTOSINE AND 5-METHYL-2''-DEOXYCYTIDINE IN AQUEOUS SOLUTION

The nucleobase 5-methylcytosine (I) is a minor component of eukaryotic DNA thought to be important in regulation of gene expression. The photochemical reactions of this nucleobase and its 2'-deoxyribonucleoside, 5-methyl-2'-deoxycytidine (II), in water have been studied. These reactions lead, respectively, to 3-amino-2-methylacrylamidine (Ib) and 3-(2-erythro-D-pentopyranos-1-yl)amino-2-methylacrylamidine (IIb) as the main photoproducts. The structure of the photoproducts was established by spectroscopic methods (1H and 13C NMR, UV spectroscopy, electron impact and liquid secondary ion mass spectrometry); in the case of Ib, confirmatory evidence was obtained by chemical methods (photolysis of 5-methyl[2-13C]cytosine, hydrolysis of N-carbomethoxy-3-amino-2-methylacrylamidine and reaction of Ib with 1,1'-carbonyldiimidazole to give I). The quantum yield for formation of Ib was determined to be 1.8 x 10(-3) at pH 7.5 while the quantum yield for formation of IIb has a lower value of 0.2 x 10(-3) at pH 7.5. These quantum yields depend strongly on pH and reach maximum values of 2.0 x 10(-3) at pH 7.0 (Ib) and 0.6 x 10(-3) at pH 5.0 (IIb). The mechanism of formation of Ib (or IIb) is proposed to involve nucleophilic attack of water on the C-2 position of photoexcited I (or II), followed by ring opening and decarboxylation of an intermediate carbamic acid.     

FLUORESCENCE AND PHOTOCHEMISTRY OF OLIGOCYTIDYLIC AND POLYCYTIDYLIC ACIDS IN AQUEOUS SOLUTION

Abstract —In addition to the monomer-like fluorescence, a long-wavelength emission (Λ^max_em= 410 nm) has been detected in the dinucleoside 5'-5' pyrophosphate (CppC) at room temperature. This emission looks very similar to that previously reported for the acidic forms of Poly C (Poly C. Poly C⁺ and Poly I. Poly C. Poly C⁺). Only the monomer-like emission (Λ^max_em= 330 nm) can be detected in neutral Poly C, acidic CppC, and the neutral or protonated forms of the dinucleoside phosphate CpC.A correlation between the room temperature fluorescence of oligo and polycytidylic acids and their photochemical behaviour is found. Irradiation of all the polymeric samples at both neutral and acid pH results in the formation of minor photoproducts. They have been characterized by their absorbance (in the range 300–400 nm) and their fluorescence spectra. The same product is obtained in all cases where the monomer-like fluorescence only is detected. Distinct products are formed in neutral CppC and in the acidic Poly C forms.
The results are discussed with respect to the conformation of the oligo and polycytidylic acids and possible relationships between the 410–420 nm emission and adduct formation. An excimer is proposed as a common, intermediate excited state in both radiative deactivation and adduct formation in neutral CppC and the acidic Poly C forms.     

RIBOFLAVIN SENSITIZED PHOTOREDUCTION OF NITRO BLUE TETRAZOLIUM ION (NBT2+) IN DEGASSED AQUEOUS SOLUTION

Abstract— When sensitized by riboflavin, the reduction of NBT²⁺ (nitro blue tetrazolium ion) takes place in both aerated and degassed aqueous solution. Laser photolysis experiments revealed that the triplet riboflavin reduces NBT²⁺ to nitro blue tetrazolinyl radical, NBT²⁺. and it disappears according to pseudo-first order kinetics, with a bimolecular rate constant of (4.2 ± 0.2) X 10⁸ M ^-1s^-1. It is shown that NBT²⁺ is not always a good detecting reagent for the superoxide anion, when the formation of the anion is mediated by riboflavin.     

PHOTOREDUCTION OF CRYSTAL VIOLET IN SOLUTION AND IN POLY(VINYL ALCOHOL) FILMS

Abstract— The photolysis of crystal violet oxalate has been studied in aqueous and non-aqueous solutions and in films of poly(viny1 alcohol) at room temperature. Evidence has been obtained from electron-spin-resonance, absorption and fluorescence spectroscopy for the formation of the semireduced dye radical, tri-( p -dimethylaminophenyl)methyl, both in solution and in the solid state. Electron spin resonance and luminescence spectra of the radical produced by electrolytic reduction of the dye are also reported.     

SENSITIZED PHOTOREDUCTION OF CO(EDTA)- IN AERATED AQUEOUS SOLUTION. ITS PHOTO-ELECTROCHEMICAL AND PHOTOBIOLOGICAL APPLICATIONS

Abstract— The reduction of Co(edta)^- in aerated aqueous solution containing 1-hydroxy-5-oxo-5H-pyrido[3,2a]phenoxazine-3-calboxylic acid (HPPC) as sensitizer and ethylenediaminetetraacetate ion(EDTA) as electron donor was studied. Semireduced HPPC, formed in a reaction between triplet HPPC and EDTA, was shown to reduce Co(edta)^- to Co(edta)^2-. The ratio of the rate constant for oxidation of semireduced HPPC by oxygen to that by Co(edta)^- was determined to be 0.45± 0.01 from competition reaction kinetics. A (concentration)half-cell (oxidation-reduction electrode) based on the photoreduction of Co(edta)^- was found to give an electrode potential decrease of 100 mV. Co(edta)^- was also found to be reduced during illumination in aerated suspension of chloroplasts. The rate of oxygen evolution for the Co(edta)^- -chloroplast system was nearly the same as that for the Fe(CN)₆^3- -chloroplast system both in the absence and presence of ammonium ions.     

三价铀的制备和稳定性研究

在盐酸和硫酸介质中,研究了汞阴极电解还原和液态Zn-Hg齐还原制备U(Ⅲ)的实验方法,比较了不同介质、酸度、铀浓度和电解时间对U(Ⅲ)还原率的影响,获得了用电解法定量还原制备U(Ⅲ)的最佳条件。经对U(Ⅲ)在空气和氮气中稳定性的测定,得出U(Ⅲ)在空气中的氧化速率呈一级反应。     

H3PO4改性PS-EDTA树脂对水相中Cu2+、Zn2+和Cd2+的吸附性能研究

大孔氯甲基化聚苯乙烯小球先后与乙二胺、2-氯乙酸反应得EDTA型螯合树脂(PS-EDTA),再用磷酸在室温处理得PS-EDTA/P树脂。PS-EDTA/P树脂被用于水相中Cu2+、Zn2+和Cd2+的吸附净化处理,探讨了溶液的pH值、初始金属离子浓度、时间、温度等因素对吸附性能的影响,并研究了其对重金属离子的吸附动力学和热力学。结果表明,PS-EDTA/P树脂对Cu2+和Zn2+的吸附符合Langmuir等温式、对Cd2+的吸附符合Freundlich等温式,准二级吸附动力学方程能够很好地描述3种金属离子在树脂上的吸附动力学行为。同时,PS-EDTA/P树脂对重金属吸附的热力学参数表明,PS-EDTA/P树脂对Cu2+、Zn2+和Cd2+的吸附是一个自发的、吸热的过程。已吸附Cu2+、Zn2+和Cd2+的树脂可以用0.1mol/L HCl解吸,解吸后的树脂对Cu2+、Zn2+和Cd2+仍具有较高的吸附量。     

硫酸铵水溶液中丙烯酰胺与正离子单体的分散共聚研究

以硫酸铵(AS)水溶液为介质,进行丙烯酰胺(AM)与正离子单体甲基丙烯酰氧乙基三甲基氯化铵(DMC)分散共聚合,制备出水溶性聚合物分散体.研究了盐浓度、分散稳定剂浓度及其分子量、单体浓度等对反应体系及分散体粒径的影响.结果表明,随着分散稳定剂的用量从6%增加到14%,分散体的平均粒径先下降,后又随之上升.分散稳定剂分子量越大,所得分散体的平均粒径越小.硫酸铵和单体的浓度对平均粒径和粒子形态等影响显著,只有在较小的范围内才能制备出粒径较均一的正离子型水溶性聚合物分散体;硫酸铵浓度越大,生成聚合物分子量越低.     

PHOTOOXIDATION OF XANTHOBILIRUBIC ACID IN AQUEOUS SOLUTION: PRODUCT AND MECHANISM STUDIES

Abstract— Xanthobilirubic acid, an oxodipyrrylmethene with a chromophore very similar to that of bilirubin, was aerobically irradiated as its sodium salt in borate buffer at pH 8. Two photooxidation products, methylethylmaleimide and 5-formyl-2,4-dimethyl-1 H -pyrrole-3-propanoic acid, were isolated. These products can be rationalized on the basis of either a Type I or a Type II (singlet oxygen) photooxygenation mechanism. The reaction is inhibited by azide, a singlet oxygen quencher, and sensitized by methylene blue. However, both the self-sensitized and the methylene blue-sensitized reactions are enhanced, rather than inhibited, by high concentrations of 1,4-diazabicyclo[2.2.2]octane, another known singlet oxygen quencher. It is therefore proposed that the diazabicyclooctane can also act as an electron donor.
The self-sensitized photooxidation of xanthobilirubic acid is an autocatalytic reaction. This is supported by the fact that addition of a previously irradiated solution to a freshly-prepared solution significantly increases the rate of photodegradation. A similar catalyst is formed, but much more slowly, from xanthobilirubic acid in the dark in the presence of oxygen.     

VISCOSITY BEHAVIOR OF LACQUER POLYSACCHARIDE IN AQUEOUS SOLUTION

The dependence of measured viscosity on NaCl concentration (0.1 to 3.0M), pH (range of 2—13) and cadoxen composition w_(cad) (from 2% to 100%) for the lacquer polysaccharide in NaCl/cadoxen/H_2O mixture containing HCl or without were obtained. All the viscosity exponents γin the Mark-Houwink equations under three different solvent condition arc close to 0.5. The w_(cad) dependence of reduced viscosity ηsp/c confirms the single strand chain of the polysaccharide. As the γvalues close to 0.5 and values of unperturbed dimension _θ/M and [η] much smaller than those for usual linear polymers, these facts suggest that the polysaccharide chains in the aqueous solutions should be dense random coil owing to the highly branched structure.     

THE ''Q-BAND'' ABSORPTION spECTRA OF HEMATOPORPHYRIN MONOMER AND AGGREGATE IN AQUEOUS SOLUTION

Abstract The resolution of the absorption spectra in the Q band (480 nm-620 nm) spectral region of monomeric and dimeric hematoporphyrin species present in aqueous solutions has been achieved using absorption, fluorescence and computer analysis methods. The absorption maxima of the dimer in this spectral region are red shifted about 12 nm with respect to those of the monomer. The significance of this finding in relationship to the well documented blue shift of hematoporphyrin aggregate observed in the Soret band region (λ_malx∼400 nm) of the absorption spectrum is discussed.     

TRANSITION METAL COMPLEXES OF AMINOPHOSPHONIC ACID ANALOGUES OF METHIONINE AND ALANINE IN AQUEOUS SOLUTION

Abstract

The stoichiometrics and stability constants of the nickel(II), copper(II) and zinc(II) complexes of l-amino-3-methylthiopropanephosphonic acid (MetP) and 1-amino-ethanephosphonic acid (a-AlaP) have been determined pH-metrically at 25°C at an ionic strength of 0.2 mol dm^?3 (KC1). From the stability data and the absorption spectra of the complexes it has been established that simple aminophosphonic acids coordinate to the nickel(II) and copper(II) ions forming chelate complexes in which the metal binding mode is bidentate with the {NH₂, PO₃ ^2-} donor set. ³¹P and ¹H NMR measurements showed that MetP and α-AlaP exhibit similar properties in the presence of zinc(II) ions, but the ligand reacts to form a cyclic phosphonoamidate in neutral and slightly alkaline solution in the Zn(II)-α-AlaP system and at slightly acidic conditions in the Zn(II)-MetP system. This difference reveals that the latter ligand at pH > 7 prefers Zn(II) coordination involving all possible (amino, phosphonate and thioether sulfur) donor groups.     

SYNTHESIS AND FLUORESCENCE STUDY OF SELF-AGGREGATION PROCESS IN AQUEOUS SOLUTION OF HYDROPHOBILIZED POLYSACCHARIDE

1.INTRODUCTIONMolecularself-assemblyorself-aggregationisthespontaneousassociationofmoleculesunderequilibriumconditionsintostable,structurallywell-definedaggregationsjoinedbynoncovalentbonds.Theself-aggregationofmoleculesleadstosupramolecularsystemsandisresponsiblefortheirfunctions.Recently,self-assemblyoraggregationofpolymeramphiphilesisofgrowinginterestwithrespecttobiologicalimportanceandpharmaceuticalorbiotechnologicalapplication.Solutionpropertiesofvariousblockcopolymerorself-aggregate…