反相胶束中辣根过氧化物酶的停流光谱研究

用停流光谱法研究了HRP在AOT、CTAB和SDS反相胶束中的吸收光谱和反应动力学，实验结果显示在AOT反相胶束中，HRP的吸收峰位置与水相中相同；而另外两种反相胶束对HRP的分子结构产生了较大影响，快速反应动力学研究显示在反相胶束中HRP形成化合物Ⅰ的速率常数远远高于化合物Ⅰ形成HRP—Ⅱ的反应速率常数，推测这是反相胶束的特殊性质造成的结果。     

水相胶束体系中底物微环境对辣根过氧化物酶催化反应…

利用荧光测活法比较了ＨＲＰ在有机相与水相胶束体系中催化不同芳香胺类的动力学常数，发现在水相胶束体系中，ＨＲＰ是在一个较严格的亲，蔬水果面进行催化反应。     

反相胶束对辣根过氧化物酶催化反应的影响

胶束体系是酶学研究比较理想的体系,因为它所具有的诸如热力学稳定、光学透明及能增溶亲水分子、亲油分子或两性分子等性质,使许多酶在胶束体系中的反应速率远远高于在水相中,即人们发现的所谓“超活性”［‘j．辣根过氧化物酶（HRP）是一种比较稳定的酶,且价廉易得,具备一般过氧化物酶的典型反应．在研究中人们发现,HRP在反相胶束体系中同样具有“超活性”,由于HRP能够催化大量底物进行反应,因此“超活性”对HRP的催化反应具有重要意义．已有研究者［’、’j对CTAB反相胶束体系中HRP的性质进行了探讨,但反相胶束对HRP的…     

两嵌段共聚物反相溶剂中组装结构转变动力学的模拟研究

利用耗散粒子动力学方法,分别研究了不同结构的组装体在改变溶剂的选择性后,在溶液及界面上的结构演变动力学.模拟结果表明,在改变溶剂的选择性后,大球形胶束在溶液中转变形成反向球形胶束,而在界面上则转变形成反向环状胶束,当前模拟结果与已有的实验结果一致.此外,模拟结果还预测出,在改变溶剂的选择性后,环状胶束在溶液中转变形成反向环状胶束,而在界面处受限形成反向的支化蠕虫状胶束;蠕虫状胶束则在溶液中转变形成反向环状胶束,而在界面处受限形成多层纳米球结构;囊泡在溶液中转变形成分散的小胶束聚集体,而在界面处受限形成球形的补丁纳米粒子.     

非水溶剂中囊泡等分子有序组合体的形成

总结了各类表面活性剂在乙醇等非水及混合溶剂中的囊泡、胶束等聚集体的形成规律,着重讨论了非水体系中介电常数改变对正负离子表面活性剂混合体系中聚集体形成的影响.对反胶束等不同分子有序组合体在非水体系中的形成情况也进行了概述.     

胶束介质中丁二酮增溶位点的室温燐光碎灭法研究

采用丁二酮室温光猝灭法研究了胶束介质中丁二酮的增溶位点，通过研究4种不同荷电和不同亲水亲脂性的光猝灭剂以及盐效应等对Stern－Volmer常数的影响，表明了二酮在SDS、CTAB的胶束中是增溶在胶团的栏栅并靠近离子头基一侧和头基／水界面附近，而在CTAB胶束中更加趋向于胶团外部头基附近．     

CTAB胶束微环境中BY增溶位置的探讨

本文用ＵＶ吸收光谱对（ＢＹ＝ＣＴＡＢ）体系胶束化过程中预胶束的形成，以及预胶束向胶束的转变过程进行了分析。采用Ｇｏｕｙ－Ｃｈａｐｍａｎ模型，建立了ＣＴＡＢ胶束微环境中ＢＹ表现解离常数与胶束结构参数之间的定量关系，根据水溶液和各种盐浓度条件下ＣＴＡＢ胶束溶液中酸碱解离常数的测量，分析了ＢＹ在ＣＴＡＢ胶束扩散层中的增溶位置，讨论了ＣＴＡＢ胶束对ＢＹ选择性吸附的特性。     

过氧化物模拟酶空间结构及介质微环境对酶催化反应的影响

在水溶液及胶束介质中分别研究了血红蛋白(hemoglobin,Hb),β环糊精氯化血红素(βCDhemin)和氯化血红素(hemin)作为过氧化物模拟酶对隐性亮绿(recessivebrilliantgreen,RBG)H2O2(或溶解氧)体系的催化特性。在Tween80存在下,通过测定米氏常数Km和Vmax,比较了酶催化活性的大小,结果表明催化活性Hb>βCDhemin>hemin。分别研究了辣根过氧化物酶(horseradishperoxidase,HRP),βCDhemin,hemin和四羧基苯基锰卟啉(MnTCPP)对4氨基安替比林(4AAP)2,3,4三氯苯酚(2,3,4trichlorophenol,TCP)体系的催化显色作用,酶及模拟酶催化活性比较为HRP>βCDhemin>hemin>MnTCPP。根据实验结果,讨论了胶束介质对RGB溶解氧催化体系的作用方式以及4AAPTCP酶催化体系的MichaeliMenten方程,并从不同空间结构(结合部位)模拟过氧化物酶催化性能的角度讨论了结合部位在酶催化反应中的有效作用。     

用温度跃升法研究胶束催化

用温度跃升快速反应动力学测试仪器,研究了合成表面活性剂SDS胶束水溶液体系与生物表面活性剂脱氧胆酸钠(NaDC)胶束水溶液体系中,金属离子Ni~(2+)-2,2′-Bipyridine(Bipy)络合物形成的动力学。实验结果表明,生物表面活性剂同样表现出程度不同的胶束催化作用。又采用假相模型处理SDS胶束体系中上述反应的动力学,由动力学结果计算出可供发生反应的胶束体积。结果表明,此体积比不加电解质的胶束溶液中的反应体积增大,此现象被认为是由无机电解质的存在所造成。     

胶束介质中丁二酮增溶位点的室温Lin光猝灭法研究

采用丁二酮室温Ｌｉｎ光猝灭法的胶束介质中下二酮的增溶位点，通过研究４种不同荷电和不同亲水亲脂性的Ｌｉｎ光猝灭剂以及盐效应等对Ｓｔｅｒｎ－Ｖｏｌｍｅｒ常数的影响，表明丁二酮在ＳＤＳ，ＣＴＡＢ的胶束中是增溶在胶团的校栅并造离子头基一侧和头基／水界面附近，而在ＣＴＡＢ胶束中更加趋向于胶团外部头基附近。     

Kinetics of fast reactions of triplet states and radicals under photolysis of 4,4′-dimethylbenzophenone in the presence of 4-halophenols in micellar solutions of sodium dodecyl sulfate in magnetic field

Quenching kinetics of the 4,4′-dimethylbenzophenone triplet state with para-substituted phenol derivatives RC₆H₄OH (R = H, F, Cl, Br, I) was studied by nanosecond laser photolysis in aqueous micellar solutions of sodium dodecyl sulfate. The kinetic data were processed in the framework of a model with the Poisson distribution of phenols between micelles. The partition constants of RC₆H₄OH between the aqueous and micellar phases and the rate constants of their escape from a micelle and quenching of the 4,4′-dimethylbenzophenone triplet state with phenols in micelles were obtained. The quenching proceeds with high rate constants through hydrogen atom transfer to form the ketyl and phenoxyl radicals (no radicals are formed in the case of 4-iodophenol), which then recombine in a micelle or escape into the outer aqueous volume. The application of an external magnetic field retards radical pair recombination in a micelle and increases the fraction of radicals escaped into the aqueous phase. The quantum yield of radical pairs decreases 2.5-fold, and the rate of their recombination in micelles increases 2.5-fold on going from 4-chloro- to 4-bromophenol. This is caused by the acceleration of triplet radical pair recombination in the solvent cage. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 6, pp. 1391–1396, June, 2005.     

Kinetic investigation of the oxidation of N-alkyl anilines by peroxomonophosphoric acid in anionic surfactant sodium lauryl sulphate

Kinetics of oxidation of N-methyl and N-ethyl aniline by peroxomono-phosphoric acid (PMPA) in aqueous and 5% (v/v) acetonitrile medium respectively have been studied in presence of anionic micelles of sodium lauryl sulphate (SLS) at different pH. Oxidation rate of both the substrates increases up to a certain [SLS] much below the critical micellar concentration (cmc) after which the rate is retarded. Kinetic data have been used to compute the binding constants of both substrate and oxidant with the micelle. A scheme explaining the kinetic data has been proposed.     

Dynamics of nitric oxide rebinding and escape in horseradish peroxidase

Ultrafast kinetic measurements of NO rebinding to horseradish peroxidase (HRP) are reported for the first time. The geminate kinetics are found to be exponential for all HRP samples studied. The ferric forms of HRP have NO geminate recombination time constants in the range of 15-30 ps, while the ferrous form has a time constant of approximately 7 ps. The simple exponential NO geminate kinetics found for HRP demonstrate that heme relaxation is not the underlying source of the nonexponential NO rebinding in myoglobin (Mb). The NO ligand escape rates from HRP are also determined, and they are found to depend dramatically on the presence or absence of the competitive inhibitor benzohydroxamic acid (BHA). The kinetic results indicate that, in contrast to Mb, there is direct solvent access to the distal heme pocket of HRP.     

Simulation of the electrical double layer of a spherical micelle of an anionic substance with regard to the solvent structure

Computer simulation methods are employed to consider the structure of the electrical double layer of a spherical micelle in aqueous surfactant solutions with allowance for the contribution of the solvent. Three micelle models were used in the calculations, namely, a macroion with discretely distributed charges and a continual solvent, a spherical model micelle with a coarse-grained representation of the solvent, and a spherical model micelle in an aqueous phase with an explicit account for water molecules. Based on these three models, the radial profiles of the local densities and electric potentials in the electrical double layer, as well as the degrees of binding single-, double-, and triple-charged counterions by the macroion in aqueous surfactant solutions, are calculated with regard to the Lennard-Jones and electrostatic interactions. The allowance for the molecular structure of the solvent leads to qualitatively different local dependences of the electric potential as compared to both the continual and coarse-grained representation of the solvent.     

Quantitative structure-activity relationship based quantification of the impacts of enzyme-substrate binding on rates of peroxidase-mediated reactions of estrogenic phenolic chemicals

The initial rates of horseradish peroxidase (HRP)-mediated enzymatic reactions of 15 assorted aqueous phase phenolic chemicals were studied. The associated reaction rate constants were found to correlate quantitatively with two independent variables: the highest-occupied molecular orbital energy (E(HOMO)) defining the intrinsic redox reactivities of the phenolic substrates and the distance between a substrate and the deltaN of HIS42's imidazole ring in an HRP/substrate binding complex, obtained through molecular simulations. Highly correlated quantitative structure-activity relationship (QSAR) equations were thus developed. This work provides insights into the impacts that HRP/substrate binding may have on HRP-mediated reactions. Additionally, the QSAR equations developed in the work may serve as a basis to further explore the potential use of HRP-mediated reactions in the treatment of estrogenic contaminants, and they constitute an important tool for redesign and screening of potential proteomic modifications to the wild-type HRP structure intended to enhance reactivity toward selected substrates.     

Studies on the Conformation of Poly(1-naphthol) Assembled by Horseradish Peroxidase in Aqueous Micelle

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Effect of AOT on enzymatic activity of the organic solvent resistant tyrosinase from Streptomyces sp. REN-21 in aqueous solutions and water-in-oil microemulsions

The effect of AOT (sodium-bis(2-ethylhexyl sulfosuccinate)) on enzymatic activity of the organic solvent resistant tyrosinase (OSRT) in aqueous phosphate buffer solutions and in water-in-oil microemulsions of the water/AOT/isooctane system has been investigated. In contrast to mushroom tyrosinase, AOT does not activate OSRT in aqueous solutions, altering its activity very little at concentrations lower than 2 mM. Increasing contents of AOT in isooctane reduce the observed initial reaction rates of oxidation of t-butylcatechol (tBC) and 4-methylcatechol (4-MC). Similarly to mushroom tyrosinase, the effect has been described using an equation based on preferential binding of the substrates by surfactant interface layers. The apparent Michaelis-Menten substrate binding constants increase linearly with AOT concentration (with slopes of 0.12+/-0.02 and 0.051+/-0.006 for tBC and 4-MC, respectively), and the effective enzyme turnover number in the microemulsions remains practically constant.     

Influence of anionic and cationic reverse micelles on nucleophilic aromatic substitution reaction between 1-fluoro-2,4-dinitrobenzene and piperidine

The nucleophilic aromatic substitution (S(N)Ar) reaction between 1-fluoro-2,4-dinitrobenzene and piperidine (PIP) were studied in two different reverse micellar interfaces: benzene/sodium 1,4-bis(2-ethylhexyl) sulfosuccinate (AOT)/water and benzene/benzyl-n-hexadecyl dimethylammonium chloride (BHDC)/water reverse micellar media. The kinetic profiles of the reactions were investigated as a function of variables such as surfactant and amine concentration and the amount of water dispersed in the reverse micelles, W0 = [H2O]/[surfactant]. In the AOT system at W0 = 0, no micellar effect was observed and the reaction takes place almost entirely in the benzene pseudophase, at every AOT and PIP concentration. At W0 = 10, a slight increment of the reaction rate was observed at low [PIP] with AOT concentration, probably due to the increase of micropolarity of the medium. However, at [PIP] > or = 0.07 M the reaction rates are always higher in pure benzene than in the micellar medium because the catalytic effect of the amine predominates in the organic solvent. In the BHDC system the reaction is faster in the micellar medium than in the pure solvent. Increasing the BHDC concentration accelerates the overall reaction, and the saturation of the micellar interface is never reached. In addition, the reaction is not base-catalyzed in this micellar medium. Thus, despite the partition of the reactants in both pseudophases the reactions effectively take place at the interface of the aggregates. The kinetic behavior can be quantitatively explained taking into account the distribution of the substrate and the nucleophile between the bulk solvent and the micelle interface. The results were used to evaluate the amine distribution constant between the micellar pseudophase and organic solvent and the second-order rate coefficient of S(N)Ar reaction in the interface. A mechanism to rationalize the kinetic results in both interfaces is proposed.     

Complexation of a hydrophobic thiazorylazophenol with Ni2+ at sodium dodecylsulfate micellar surface

Complexation of thiazorylazododecylphenol (TADP) with Ni2+ at the surface of sodium dodecylsulfate (SDS) micelles has been spectrophotometrically studied. Complicated spectral changes are analyzed by a factor and multivariate analysis, which implies the formation of [TDAP(OH-)Ni]0 as well as a simple 1:1 complex of Ni2+ with TDAP at the micellar interface. All of the equilibrium constants required to describe this system are substantially affected by electrolyte concentrations. Coexistent electrolytes vary the surface potential of the micelle, and in turn influence the equilibria taking place on the micellar surface. The electrostatic potential estimated based on the equilibrium shifts is more negative than that calculated according to Poisson-Boltzmann theory, which simply involves electrostatic effects. This disagreement is possibly caused by different aqueous environments around the micelle from bulk solution, which also facilitate the formation of unusual complex such as [TDAP(OH-)Ni]0.