LIGHT-DEPENDENT AND LIGHT-INDEPENDENT PRODUCTION OF HYDROGEN GAS BY PHOTOSYNTHESIZING RHODOSPIRILLUM RUBRUM MUTANT C

Abstract. Rhodospirillum rubrum mutant C grew photosynthetically in the light and produced copious amounts of H₂. During light-growth mutant C produced 7.9mmol of H₂ in medium with 9mmol of Na-pyruvate per mg protein. When parent strain R. rubrum S ₁ was grown similarly, these cells only produced a trace amount of H₂. Light-grown mutant C evolved H₂ by H₂-nitrogenase and formic hydrogenlyase. Although both hydrogenases were previously detected in R. rubrum S₁, the activities of the reactions in light-grown mutant C were higher and they operated under different conditions. In the parent strain S₁, the production of nitrogenase was strongly repressed during growth in medium enriched with organic nitrogen and the cells only reduced 0.06 pmol of acetylene per mg protein after 30 min in the light. Under similar conditions, nitrogenase activity measured by the acetylene reduction test in mutant C was 10-fold greater. In addition to nitrogenase, mutant C also produced large amounts of H₂ with formate as an intermediate when the cells were grown with Na-pyruvate. Formic hydrogenlyase in mutant C operated equally well in anaerobic light or dark conditions. The analogous formate oxidation reaction in parent strain S₁ only functioned in the dark. These data, compared with results with R. rubrum S₁ suggested that C was a regulatory mutant. Additional observations suggested that formic hydrogenlyase occurred constitutively in R. rubrum . Pyruvate formate-lyase, however, which produced formate for formic hydrogenlyase, was only detected in the cells after growth in media with Na-pyruvate. The reaction was not formed when R. rubrum was grown in the light in media with dl-malate as the sole carbon substrate.     

MECHANISM OF FORMATION OF FORMALDEHYDE IN THE FLASH PHOTOLYSIS OF METHYL FORMATE

Abstract —From flash photolyses of methyl formate (HCOOCH₃), d -methyl formate (DCOOCH₃), methyl formate- d ₃ (HCOOCD₃) and fully ***deuterated methyl formate (DCOOCD₃) in the vapour phase at room temperature, the relative efficiencies of the formyl and methoxyl radicals in producing formaldehyde have been determined.     

A HIGHLY REACTIVE HETEROATOM ANALOG OF RETINAL AND ITS INTERACTION WITH BACTERIORHODOPSIN

Abstract— C₁₈ formate ester (5) [2-(6-methyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3E,5E,7E-octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (t_l/2= 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm^-1) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C₁₈ alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester-treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV-visible absorption, suggesting that a covalent bond between the C₁₈ moiety and a nucleophilic group of the protein has probably formed.     

Cyclic and stripping voltammetry of tin at mercury hanging drop and film electrodes in acidic o-diphenol media in the presence of lead and cadmium

The influence of catechol, gallic acid and tiron on the voltammetric behaviour of tin(IV) in the presence of lead(II) and cadmium(II) was investigated at hanging drop and mercury film electrodes in perchloric acid, oxalic acid and formate supporting electrolytes. Under cyclic conditions, well separated peaks of tin, lead and cadmium are obtained in oxalic acid and formate solutions containing gallic acid or catechol; tiron suppresses the tin peaks significantly. The efficiency of the deposition of tin in the presence of catechol or gallic acid is less than that of lead, particularly at long deposition time. The best separation of the stripping peaks of tin, lead and cadmium is obtained in oxalic acid solution containing gallic acid or catechol. In perchloric acid solution containing gallic acid or catechol the second peak corresponding to tin oxidation is useful for determinations of tin in the presence of lead. Tin(IV) at the 10^-8 mol l^-1 level can be detemined in various salt solutions and in water samples in the presence of five-fold amounts of lead and cadmium.     

A HIGHLY REACTIVE HETEROATOM ANALOG OF RETINAL AND ITS INTERACTION WITH BACTERIORHODOPSIN

Abstract
C₁₈ formate ester (5) [2-(6-methyl-8-(2,6,6-trimethyl-1-cyclohexen-1-yl)-3E,5E,7E-octatrienyl formate], a highly reactive analog of retinal, was synthesized and its interaction with bacterioopsin studied. The formate ester, in the absence of purple or bleached membrane, undergoes very rapid reaction (t_l/2= 0.9 min) in neutral buffer but with membrane present it diffuses more rapidly into the membrane where it reacts slowly. Incorporation of 5 in the membrane results in a 38 nm (3900 cm^-1) red shift which remains after reconstitution with retinal. Similar experiments with the corresponding C₁₈ alcohol (4) results in a red shift, but this absorption blue shifts upon reconstitution with retinal. Washing the formate ester-treated membrane with bovine serum albumin or the corresponding lyophilized preparation with hexane, treatments that remove retinal oxime, fails to remove the UV-visible absorption, suggesting that a covalent bond between the C₁₈ moiety and a nucleophilic group of the protein has probably formed.     

甲酸存在下硝酸根在二氧化钛表面光催化还原成氨

用甲酸作空穴清除剂,研究了ＴｉＯ２水悬浮体系中硝酸根光催化还原氨的反应。与草酸作空穴清除剂相比,甲酸加速硝酸根的还原更显著。研究了硝酸根和甲酸根的浓度效应及ｐＨ效应。实验结果表明,硝酸根在ＴｉＯ２表面的吸附是加附是加速该光催化还原反应的重要因素。     

REEVALUATION OF THE SPECTRAL AND KINETIC PROPERTIES OF HO2 AND O2- FREE RADICALS

Abstract— The spectra and molar absorbances of the HO₂ and O₂^- free radicals have been redetermined in aqueous formate solutions by pulse and stopped-flow radiolysis as well as by ⁶⁰Co gamma-ray studies. The extinction coefficients at the corresponding maxima and 23°C are ²²⁵= 1400 ± 80 M ^-1 cm^-1 and ²²⁵= 2350 ± 120 M ^-1 cm^-1 respectively. Reevaluation of earlier published rate data in terms of the new extinction coefficients yielded the following rate constants for the spontaneous decay of HO₂ and O₂^-: K _Ho2+HO2= (8.60 ± 0.62) × 10⁵ M ^-1 s^-1; K _Ho2+O2-= (1.02 ± 0.49) × 10⁸ M ^-1 s^-1; K _Ho2+O2- < 0.35 M ^-1 s^-1. For the equilibrium HO₂→ O₂^-+ H⁺ the dissociation constant is K _Ho2= (2.05 ± 0.39) × 10^-5 M or p K _HO2= 4.69 ± 0.08. G (O₂^-) has been evaluated as a function of formate concentration.     

GAMMA AND PULSE RADIOLYSIS STUDIES OF THE REACTION BETWEEN SUPEROXIDE IONS AND OXYHEMOGLOBIN-METHEMOGLOBIN SYSTEM

Abstract— The radiolytic studies of oxyhemoglobin or methemoglobin in neutral aerated aqueous solutions with formate ions, lead to three conclusions:
The oxidation of oxyhemoglobin by O^-₂ is not important. The observed low oxidation yield is probably due to the slow reaction with hydrogen peroxide produced by O^-₂ disproportionation.
The reduction of methemoglobin in γ radiolysis reaches a plateau which could be explained by structural considerations.
The reduction of methemoglobin by O^-₂ ions, if it occurs, is relatively slow: k = 1.4 × 10³ M ^-1 s^-1. But a problem remains concerning the spectral characteristics of the product.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS–XII. SPIN TRAPPING STUDY OF THE FREE RADICALS GENERATED DURING THE PHOTOLYSIS OF PHOTO ALLERGENS BITHIONOL and FENTICHLOR

Free radicals were trapped and observed by ESR when photoallergens bithionol and fentichlor were irradiated in the presence of spin traps N- t -butyl-α-phenylnitrone (PBN) and 5,5-dimethyl-pyrroline-N-oxide (DMPO). In the absence of air, both PBN and DMPO trapped a carbon-centered radical. The carbon-centered radical, which was capable of abstracting a hydrogen atom from cysteine, glutathione, ethanol and formate, was identified as an aryl radical derived from the homolytic cleavage of the carbon-chlorine bond. In the presence of air, both carbon-centered radicals and hydroxyl radicals were trapped by DMPO. Under similar conditions, the yield of the hydroxyl radicals was greater from bithionol than from fentichlor. The presence of the hydroxyl radical was confirmed by kinetic experiments employing hydroxyl radical scavengers (ethanol, formate). Superoxide and H₂O₂ were not involved. Experiments with oxygen-¹⁷O indicated that the hydroxyl radicals came exclusively from dissolved oxygen. The precursor of the hydroxyl radical is postulated to be a peroxy intermediate (ArOO*) derived from the reaction of an aryl radical (Ar*) with molecular oxygen. Both bithionol and fentichlor photoionized only when excited in the UVC (<270 nm) region. Free radicals have long been postulated in the photodechlorination of bithionol and fentichlor and the present study provides supporting evidence for such a mechanism. Aryl and hydroxyl radicals are reactive chemical species which may trigger a series of events that culminate in photoallergy.     

RADICAL GENERATION DURING THE ILLUMINATION OF AQUEOUS SUSPENSIONS OF TUNGSTEN OXIDE IN THE PRESENCE OF METHANOL, SODIUM FORMATE and SODIUM BICARBONATE. DETECTION BY SPIN TRAPPING

Abstract— Free radical intermediates appearing during illumination of aqueous suspensions of tungsten oxide were detected by electron spin resonance using the technique of spin trapping. Solutions irradiated contained methanol, formaldehyde, sodium formate and sodium hydrogen carbonate. Signals assigned to the spin adducts of the •H, •OH, •CO₂^- and •CH₂OH radicals were found.     

SPECTROSCOPIC STUDIES OF CUTANEOUS PHOTOSENSITIZING AGENTS—II. SPIN TRAPPING OF PHOTOLYSIS PRODUCTS FROM SULFANILAMIDE AND 4-AMINOBENZOIC ACID USING 5,5-DIMETHYL-1-PYRROLINE-1-OXIDE

Abstract— The photodecomposition of sulfanilamide, 4-aminobenzoic acid and related analogs in aqueous solution has been studied with the aid of spin traps 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) and CH₃NO₂ as well as by direct electron spin resonance techniques. The NH₂ radical was trapped by DMPO during the photolysis of aqueous solutions of sulfanilamide with a Xe arc lamp. Studies with [¹⁵N¹]-sulfanilamide indicated that the NH₂ radical was generated by homolytic fission of the sulfur-nitrogen bond. Under the same conditions DMPO trapped the H and SO⁻₃ radicals during photolysis of sulfanic acid. Direct photolysis of sulfanilamide, sulfanilic acid and Na₂SO₃ in the absence of any spin trap yielded the SO⁻³ radical. Photolysis of 4-aminobenzoic acid at pH 7 gave the H radical which was trapped by DMPO. At low pH values OH and C₆H₄COOH radicals were generated during the photolysis of 4-aminobenzoic acid. No e⁻_aq were trapped by CH₃NO₂ when acid (pH 4) and neutral aqueous solutions of sulfanilamide or 4-aminobenzoic acid were photoirradiated. The mechanism of formation of known photoproducts from the free radicals generated by sulfanilamide and 4-aminobenzoic acid during irradiation are discussed. The free radicals generated by these agents may play an important role in their phototoxic and photoallergic effects.     

Oxidation of Formic and Oxalic Acids in an Electrodeless Electrochemical Reaction

Decomposition of formic and oxalic acid and of sodium formate and sodium oxalate (0.1 M solutions) in an electrodeless electrochemical reaction was studied. The oxidation kinetics was analyzed in terms of the previously developed model. The decomposition yields of formic acid and sodium formate are 0.5 and 1 molecule/(100 eV), respectively, which is comparable with the radiation-chemical decomposition yield, taking into account the installation efficiency.     

Dissolution of kaolinite induced by citric, oxalic, and malic acids

Kaolinite is a dominant clay mineral in the soils in tropical and subtropical regions, and its dissolution has an influence on a variety of soil properties. In this work, kaolinite dissolution induced by three kinds of low-molecular-weight organic acid, i.e., citric, oxalic, and malic acids, was evaluated under far-from-equilibrium conditions. The rates of kaolinite dissolution depended on the kind and concentration of organic acids, with the sequence R(oxalate)>R(citrate)>R(malate). Chemical calculation showed the change in concentration of organic ligand relative to change in concentration of organic acid in suspensions of kaolinite and organic acid. The effect of organic acid on kaolinite dissolution was modeled by species of organic anionic ligand. For oxalic acid, L(2-)(oxalic) and HL(-)(oxalic) jointly enhanced the dissolution of kaolinite, but for malic and citric acids, HL(-)(malic) and H2L-(citric) made a higher contribution to the total dissolution rate of kaolinite than L(2-)(malic) and L(3-)(citric), respectively. For oxalic acid, the proposed model was R(Si)=1.89x10(-12)x[(25x)/(1+25x)]+1.93x10(-12)x[(1990x1)/(1+1990x1)] (R2=0.9763), where x and x1 denote the concentrations of HL(oxalic) and L(oxalic), respectively, and x1=10(-3.81)xx/[H+]. For malic acid, the model was R(Si)=4.79x10(-12)x[(328x)/(1+328x)]+1.67x10(-13)x[(1149x1)/(1+1149x1)] (R2=0.9452), where x and x1 denote the concentrations of HL(malic) and L(malic), respectively, and x1=10(-5.11)xx/[H+], and for citric acid, the model was R(Si)=4.73x10(-12)x[(845x)/(1+845x)]+4.68x10(-12)x[(2855x1)/(1+2855x1)] (R2=0.9682), where x and x1 denote the concentrations of H2L(citric) and L(citric), respectively, and [Formula: see text] .     

FLUORESCENCE QUENCHING OF INDOLIC COMPOUNDS BY ALIPHATIC AMINO ACIDS. EVIDENCE FOR EXCITED STATE COMPLEXES

Abstract The fluorescence quenching of indole, tryptophan, tryptamine and indole-3-acetic by aliphatic amino acids was studied. The bimolecular rate constant ( k _q) for the deactivation of the excited state was determined. The k _q values were in the range 0.6 × 10⁸–1.6 × 10⁹ M ^–1 S^–1 and they increased in the order tryptophan < tryptamine < indole ≈ indole-3-acetic acid. When the rate constant was corrected for diffusion al effects a good linear correlation was found between the log ( k '_q) and the ionization equilibrium constant of the carboxylic group of the amino acid (p ^k _a1). This was interpreted as arising from a charge transfer mechanism in which the indole moiety acts as an electron donor and the carbonyl group of the amino acid as the acceptor.
The activation parameter for the quenching processes were also determined. The ΔH^≠ values were in the range —4.0 to +4.0 kcal/mol and the ΔH^≠ in the range –7 to –37 e.u. For the systems with lower values of k _q negative values for ΔH^≠ were observed. A good enthalpy-entropy compensation was found with an isokinetic temperature of 229 K. These results suggest that a common mechanism is operating for all the systems and that it involves the formation of an excited state complex between the indolic compound and the amino acid.     

逐级提取-高效液相色谱法快速测定植物组织中8种有机酸

针对植物组织中草酸存在的不同形态,建立了水和稀盐酸作为提取介质的逐级提取方法,获得了水溶态和酸溶态草酸及乙醇酸、乙醛酸、酒石酸、苹果酸、乙酸、柠檬酸、琥珀酸等有机酸。采用Hypersil ODS (200 mm×4.6 mm, 5 μm)色谱柱,以5 mmol/L磷酸二氢钾水溶液(pH 2.8)作为流动相,在进样量5 μL、检测波长210 nm、柱温30 ℃的条件下,通过分时段控制流速实现了8种有机酸的快速分离,同时去除了盐酸对酸溶态草酸测定的干扰。本方法精确灵敏、回收率高、重复性好,可应用于实际样品的测定分析。     

结冰过程对溶解性有机质典型组分还原Cr(Ⅵ)的影响

研究了结冰过程对溶解性有机质(DOM)的4种典型组分草酸、 酒石酸、 苹果酸和柠檬酸还原Cr(Ⅵ)的影响. 结果表明, 在低浓度下Cr(Ⅵ)在水溶液中不能被4种有机酸所还原; 而在冰中, 不同的有机酸对Cr(Ⅵ)的去除均有促进作用, 且去除效果随着有机酸浓度的增大逐渐增强. 4种有机酸的作用效果强弱顺序为草酸>酒石酸>苹果酸>柠檬酸. 通过使用不同浓度的无机盐和无机酸可以改变冰表面上类似液体层的厚度来抑制Cr(Ⅵ)的还原, 作用效果与无机盐种类无关. 溶液的初始pH值和有机酸结构是影响Cr(Ⅵ)还原的重要因素. 实验条件下冷冻浓缩效应的富集倍数至少可达10³, 对冰中草酸去除Cr(Ⅵ)有明显的促进作用.     

Radium desorption, manganese and iron dissolution from sand filters of a conventional ground water treatment plant under reductive conditions

Summary Sand filters are used as a filter bed in many ground water treatment plants to remove the physical contaminants and oxidation products. A build-up of radioactivity may take place on the granules, where iron and manganese oxides are deposited and form thin films on the surface of sand filter. The oxides of iron and manganese play an important role in adsorbing radium from ground water. The disposal of those granules makes a significant problem. A batch technique is used for solubilization of radium from sand filters in the presence of some organic acids, which act as reducing agents. These acids are formic acid, acetic acid, benzoic acid, succinic acid, oxalic acid, phthalic acid, and adipic acid. The data were obtained as a function of acidity, temperature, contact time and liquid/solid ratio particle size and shaking speed. It was found that oxalic acid was the best for radium removal. The effectiveness of these acids on radium removal was as follows: oxalic acid > phthalic acid > adipic acid > succinic acid > formic acid > acetic acid. The maximum removal obtained was 69.9% at 1M oxalic acid at 8 ml/g ratio. Reaction kinetics and mechanism parameters of the dissolution process were studied and compared with other published data.     

CHLORIDE ENHANCEMENT OF QUENCHING OF TRIPLET METHYLENE BLUE BY Fe(II)

Abstract— The influence of chloride ion on the rate of decay of triplet methylene blue in 0.01 M acid in the absence and presence of ferrous ions was investigated by means of laser flash-photolysis monitored by kinetic spectrophotometry. Chloride weakly accelerates decay of ³MBH^2± in aqueous solution in the absence of Fe(II). Quenching of ³MBH²⁺ by Fe(II) is more strongly catalyzed by Cl^- in both water and 50 v/v% aq. CH₃CN. The uncatalyzed quenching constant, k ₅, is of the order of 1 × 10⁶ M ^-1 s^-1 while in 4.8 M aqueous chloride ( μ – 7.2 M ) k ₅= (37.2 ± 1.8) × 10⁶ M ^-1 s^-1. A possible role of chloride is as a bridging species in quenching via electron transfer between ³MBH²⁺ and Fe(II).     

THE EFFECT OF MOLECULAR POLARIZATION ON THE ELECTROCHROMISM OF CAROTENOIDS—I. THE INFLUENCE OF A CARBOXYLIC GROUP

Abstract— Electrochromism of oriented all- trans -β-apo-8'-carotenoic acid is studied in thin capacitors. The linear electrochromism is very strong, in contrast to that of symmetrical carotenoids. It is proportional to the first derivative of the absorption spectrum. The quadratic electrochromism can be described as a superposition of fractions proportional to the first and second derivatives of the absorption spectrum. The permanent dipole moment difference between the ground state and the excited state of the carotenoic acid molecule is Δμ= 3.6 × 10^-29 C·m (±20%) (10.7 Debyes). The polarizability difference parallel to the long axis of the molecule is Δα|| = 1.17 × 10^-37 C·m²·V^-1 (±20%) (1050 ų). Furthermore, the relative permittivity of the solid carotenoic ethyl ester is _r= 3.5 ± 0.2.
Δμ is due to the polarizing force of the carboxylic group. This force is equivalent to a mean local electric field of F _t≅3 × 10⁶V/cm. Such a "local field" may also be exerted on a symmetrical carotenoid in the membrane of photosynthesis, e.g. by asymmetrical complex formation with a polarizing molecule. To obtain an effective permanent field of F _p≅ 2 × 10⁶V/cm across the membrane, as postulated in photosynthesis, a local field of F _l≅ 5.5 × 10⁵ V/cm would be sufficient. F _p is shown to be directed from inside to outside of the thylakoid. To realize this, e.g. a positive polar (i.e. electron-attracting) complex partner of the carotenoid, located more to the inside of the thylakoid, can be postulated.     

CHEMICAL REACTION RATES OF AMINO ACIDS WITH SINGLET OXYGEN

Abstract— The chemical reactions of amino acids with singlet oxygen have been measured in D₂O solution where the singlet oxygen was generated directly by irradiation of the oxygen ³∑_g^-→¹δ_g+ lv electronic transaction with the 1.06 μm output of an Nd-Yag laser. Chemical reaction was measured as amino acid loss by an amino acid analyzer or by fluorescence in the cases of tryptophan and tyrosine.
The chemical rate constants, in units of 10⁷ M ^-1s^-1, are histidine 10, tryptophan 3, methionine 1.7, tyrosine 0.8 and alanine 0.2, In the cases of histidine, methionine and alanine the interaction appears to be entirely chemical, i.e. there is no evidence for physical quenching in addition to the chemical reaction. The histidine chemical reaction rate constant shows an increase with pD with a p K of 6.9.