LASER FLASH SPECTROSCOPY OF METHYLENE BLUE WITH NUCLEIC ACIDS. EFFECTS OF IONIC STRENGTH AND pH

Laser flash spectroscopic measurements were made on methylene blue complexed to the synthetic polynucleotides poly[d(G-C)] and poly[d(A-T)] in solutions of varying ionic strength and pH. Triplet decay rates and rates of triplet quenching by oxygen have been measured for the polymer/dye solutions. The triplet decay and oxygen quenching rates of methylene blue in complex with poly[d(A-T)] are much less sensitive than those with poly[d(G-C)] with respect to variations in ionic strength. It is also shown that protonation of the triplet state of MB+ with poly[d(A-T)] is slower than that of free dye. These results indicate strong binding of the dye to poly[d(A-T)]. Excitation of the MB+/poly[d(A-T)] complex at 665 nm yielded single exponential decay kinetics, in contrast with excitation at 600 nm where double exponential kinetics were measured. This is tentatively assigned to excitation of dye dimer bound to this polymer.     

THE PHOTOREDUCTION OF METHYLENE BLUE BY AMINES—I. A FLASH PHOTOLYSIS STUDY OF THE REACTION BETWEEN TRIPLET METHYLENE BLUE AND AMINES

Abstract— Flash photolysis was used to study the reduction of the triplet state of methylene blue by both alkyl- and aryl-amines. The extent of the formation of the semireduced form of the dye yielded rate constants of interaction between the triplet state and the amine ( k ₅). A correlation between log k ₅ and ionization potentials for alkylamines (slope = -1.75 eV^-1) was interpreted as evidence for the formation of a partial charge-transfer intermediate. The rate constants ( k ₅) calculated for aryl-amines approached the rate of diffusion in many cases. A Hammett plot for a series of N, N-dimethyl-anilines yielded a moderately large p value (– 3.28) consistent with the formation of a charge-transfer intermediate. It was concluded that reaction of amines with triplet methylene blue leads to the formation of a partial charge-transfer intermediate which may undergo complete electron transfer to yield radicals, or undergo spin inversion and return to the ground state.     

LASER FLASH PHOTOLYSIS OF INDOLE IN THE PRESENCE OF AMINO ACIDS

The laser flash photolysis of indole at 265 nm in the presence of glycine, proline and hydroxy proline was studied. The relative yields of c _aq, triplet state, and indole cation radical were determined in the absence and in the presence of the amino acids. The yields were determined as a function of laser intensity and the values at very low intensity were compared with the fluorescence quenching results. It was concluded that in these conditions the photoionization of indole occurs via the fluorescent state. From the curves of triplet yield vs laser intensity, the triplet quantum yield extrapolated at low laser intensity was obtained, φr = 0.55 φ 0.05, relative to the literature value of 0.15 for φ_eag. This gives φ_F+φ_eaq= 1.0 ± 0.1 at room temperature. When proline and hydroxy proline were used as singlet quenchers, the yield of In was greater than the yield of c_aq. This was considered as evidence that a fraction of the quenching processes leads to complete electron transfer from indole to the amino acids.     

等色染料离子对—溴酚蓝.亚甲蓝体系萃取光度法测定镍

研究了利用溴酚蓝与亚甲蓝所形成的等色染料离子对萃取测定镍的方法。用酸将l,2-二氯乙烷中的Ni(phen)_3·BPB解析后,并加入与溴酚蓝颜色相近的亚甲蓝。利用1,2-二氯乙烷中溴酚蓝·亚甲蓝的染料离子对协同增敏效应提高了测定镍的灵敏度,其摩尔吸光系数ε=1.58×10~5。镍量在4×10~(-7)～2×10~(-5)mol·L~(-1)的范围服从比耳定律。方法用于测定标样ZDL—109中镍的含量,相对标准偏差为3.5％。     

REACTIONS OF PHOTOEXCITED METHYLENE BLUE

Abstract— Some reactions of methylene blue (oxidized form) excited by visible light, were investigated at 25°C in dilute and deaerated aqueous solutions. Under these conditions, methylene blue causes oxidation of sodium ascorbate, ferrocytochrome c and ethylenediamine tetraacetate (in air), as determined spectrophotometrically. Most of these reactions showed measurable reversibility in the dark. Chelation with divalent ions inhibited the photoxidation of ethylenediamine tetraacetate. Ferricytochrome c was reduced by excited methylene blue. The buffers used in the above reactions (Tris-HCl or sodium phosphate) appeared to participate in these photoexcited systems. Inhibitors are described for the methylene blue-ascorbate photoreaction.     

亚甲基蓝为介体的甲胎蛋白免疫传感器的研制及应用

构建了快速测定血清中甲胎蛋白(AFP)含量的电流型免疫传感器,该免疫传感器是用壳聚糖固定电子媒介体亚甲基蓝和辣根过氧化物酶(HRP)标记的甲胎蛋白抗体于一次性丝网印刷碳电极(SPCE)表面制备而成。当该免疫传感器在含AFP样品的溶液中于30℃培育40 min后,抗原抗体的免疫结合会导致HRP标记对过氧化氢电催化氧化的效率降低。在优化的测定条件下,催化效率的降低与AFP浓度在5.0~110.0μg.L-1范围内呈线性关系,免疫分析的检出限为1.4μg.L-1(3σ)。对免疫传感器的精密度作了试验,同一支传感器测试结果的相对标准偏差为6.6%;当取3支用同一方法制备的传感器进行测试时,相对标准偏差为9.3%。放置7d后,传感器对AFP的响应值相当于初试值的88%,在pH 7.0的缓冲溶液中的还原电流为原值的96%。     

LASER FLASH PHOTOLYSIS OF EOSIN AND ITS COMPLEX WITH LYSOZYME

Abstract— The transient absorption spectra of aqueous solutions of eosin and of the lysozyme-eosin complex have been examined after excitation with a Q -switched frequency-doubled (347 nm) ruby laser pulse. Eosin itself gives three broad, intense short-lived absorption bands with maxima at wavelengths of 410, 460 and 580 nm, which other workers have identified with the semi-reduced and semi-oxidized radicals and the triplet state of the dye, respectively. In the complex with lysozyme, the yield and lifetime of the eosin triplet are greatly reduced in comparison with the free dye. It is suggested that excited eosin, when bound to lysozyme, decays mainly from the singlet state by pathways such as charge transfer which are not available to the free molecule.     

THE PHOTOREDUCTION OF METHYLENE BLUE BY AMINES—II. AN INVESTIGATION OF THE DECAY OF SEMIREDUCED METHYLENE BLUE

Abstract— The decay of semireduced methylene blue (MB') formed in the photoreduction of the dye by aryl- and alkylamines was examined by flash photolysis. The second order decay of MB in methanol produced using arylamines and 1,4-diazabicyclooctane as photoreducing agents led to complete regeneration of the dye and amine. The rate constants for a series of N.N-dimethylanilines showed a small substituent effect ( p = 0.69 ± 0.16) compatible with recombination of MB' with arylamine derived radical cations. A study of the solvent effect on the recombination process revealed the importance of the stability of the radical cation toward the solvent and also indicated that the reaction approaches the rate of diffusion. The photoreduction of the dye by most alkylamines examined resulted in permanent bleaching of methylene blue. The second order decay of MB' produced using tertiary aliphatic amines led exclusively to formation of the leuco-dye with no apparent regeneration of methylene blue; this process was tentatively assigned to a reaction of MB' with α-amino radicals formed from the amine radical cation. It was concluded that the methylene blue-sensitized photooxidation of amines involves a Type I process and possible mechanisms are discussed.     

PHOTOREDUCTION OF METHYLENE BLUE BY WATER*

Abstract— The photoreduction of methylene blue in acid solution has been studied electrochemically. It has been found that methylene blue photoreduction proceeds in red light, with only water available as reducing agent. Reaction energy considerations require two photons to reduce each methylene blue molecule. A two-photon mechanism involving a long-lived dimer intermediate is proposed, and is shown to lead to the observed kinetics, including the dependence of rate on light intensity and methylene blue concentration.     

THE PHOTOREDUCTION OF METHYLENE BLUE BY ARYLAMINOMETHANE-SULFONATES

Abstract— The photoreduction of methylene blue in the presence of arylaminomethanesulfonates (RAMS = RC₆H₄NHCH₂SO₃Na) was studied by laser and conventional flash photolysis. These compounds quenched the methylene blue triplet deviating from a normal Stern-Volmer behaviour. For low quencher concentrations, a Rehm-Weller relationship was found between the k _q's and the DL G 's obtained for the electron transfer reactions. The lack of further quenching at higher [RAMS] is ascribed to the formation of a ground state ion pair between the dye and the anionic quencher which, on excitation, forms a triplet state unable to under go electron transfer for steric reasons. A second order decay rate constant was found for the semireduced species (MB') ( ca. 5 × 10⁹ M _-1 s_-1, independent of the RAMS used) and is attributed to a proton transfer from the radical zwitterion (RC₆H₄NH CH₂SO₃⁻) to MB. The overall dependence on the substituent of the bleaching observed by continuous irradiation follows the triplet behaviour.     

A LASER FLASH PHOTOLYSIS STUDY OF THE NATURE OF FLAVIN MONONUCLEOTIDE TRIPLET STATES AND THE REACTIONS OF THE NEUTRAL FORM WITH AMINO ACIDS

Abstract— Primary photochemical processes in aqueous solution have been characterised for FMN. The influence of pH on these processes is attributed to protonation of the neutral triplet and not to the presence of a dimeric species as postulated earlier. Second order rate constants for reaction between the neutral triplet and some naturally occurring amino acids are reported.     

两点电位滴定法测定染料亚甲基蓝的含量

将两点电位滴定法应用于亚甲基蓝等含可电离氯离子的碱性染料的测定。只需在滴定终点前附近记录两次AgNO3标准溶液体积和相应的电极电位值,利用两点法公式计算滴定终点,从而确定亚甲基蓝含量,此法简便、灵敏、准确。     

亚甲蓝分光光度法测定水体中的阴离子表面活性剂

利用三氯甲烷萃取水体样品中的阴离子表面活性剂，用50mL比色管代替50mL容量瓶对三氯甲烷萃取液进行定容，以亚甲蓝分光光度法进行测定。该方法操作简便，测定阴离子表面活性剂的线性范围为0．150～1．70mg／L，检出限为0．050mg／L，样品加标回收率为89％～98％。     

盐卤硼酸盐化学──ⅩⅩⅧ.氯柱硼镁石的激光拉曼光谱

本文研究了氯柱硼镁石硼酸和硼砂的晶体和它们在水溶液中的激光拉曼光谱,并与某些阴酸盐的谱图进行对比.初步提出硼氧配阴离子的聚合形式,为进行氯柱硼镁石结构分析提供实验依据.     

盐卤硼酸盐化学──ⅩⅩⅧ.氯柱硼镁石的激光拉曼光谱

本文研究了氯柱硼镁石硼酸和硼砂的晶体和它们在水溶液中的激光拉曼光谱，并与某些阴酸盐的谱图进行对比．初步提出硼氧配阴离子的聚合形式，为进行氯柱硼镁石结构分析提供实验依据．     

钠基膨润土吸附亚甲基蓝热力学与动力学研究

利用钠基膨润土吸附亚甲基蓝水溶液,探讨了不同参数如接触时间、初始pH值、温度等对其吸附性能的影响。结果表明,室温下,pH10,钠基膨润土吸附60min,其吸附量达198.71mg/g,且吸附量随温度的升高而增大。通过计算不同温度下的热力学参数?G,?H和?S,证实该吸附为一自发的吸热过程。其等温吸附平衡更符合Langmuir模型;吸附动力学更适合准二级反应方程。