ON THE SUMMATION OF QUANTA FOR THE PHOTOIONIZATION OF TYROSINE AND TRYPTOPHAN IN ALKALINE SOLUTIONS AT 80°K

Abstract— Some results of a study of the summation of quanta for the photoionization of tyrosine and tryptophan in frozen alkaline solution are presented. By means of a double-beam irradiation method it has been shown that the photoionization of aromatic amino acids in such solutions proceeds via a triplet state intermediate.     

PHOTOIONIZATION OF CRYSTAL VIOLET IN AQUEOUS SOLUTION

Abstract— Laser flash photolysis studies were carried out on a triphenylmethane dye, crystal violet (CV⁺), at 248 nm in aqueous solutions. The results show that CV⁺ undergoes photoionization and the resulting transients CV^-2+, hydrated electrons (e^-_aq) and CV⁺ radical formed by the reaction of e^-_aq with CV⁺ have been characterized. Studies using suitable scavengers were done to support the characterization of the transient species. Laser intensity effects show that the ionization is biphotonic. Two mechanisms are proposed to explain the observed photoionization involving higher excited singlet state and/ or another long-lived excited state of the dye.     

ISOLATION AND IDENTIFICATION OF TRYPTOPHAN PHOTOPRODUCTS FROM AQUEOUS SOLUTIONS OF TRYPTOPHAN EXPOSED TO NEAR-UV LIGHT*

Abstract—One of the previously unidentified photoproducts isolated from the photolysate of aqueous tryptophan solutions was identified as 2-carboxy-3a-hydroxy-1,2,3,3a,8,8a-hexahydropyrrolo(2,3b)-indole by direct comparison with the authentic reference compound synthesized using the established procedure. This pyrroloindole alcohol has been shown to be the reduction product of the 3a-hydroperoxy intermediate (structure 4 in Fig. 1) by Nakagawa et al . (1977). The isolation and identification of this derivative and the detection of the peroxy intermediate 3a-hydroperoxypyrrolidinoindole ( 4 ). from irradiated aqueous tryptophan solutions suggests that the direct photooxidation of l -tryptophan to fromylkynurenine may follow a pathway via a tricyclic intermediate instead of the energetically unfavorable dioxotane intermediate. This scheme is similar to the mechanistic model proposed by Nakagawa et al . (1977) for the rose bengal sensitized photooxidation of tryptophan.     

壳聚糖在水溶液中的辐射降解反应

研究了壳聚糖在CH3COOH/NaCl缓冲溶液均相体系下的辐射降解反应,给出了H2O2、异丙醇、pH、样品初始分子量等因素对壳聚糖降解的影响,探讨了实验条件下溶液中不同自由基对壳聚糖降解的作用,并对辐照前后壳聚糖的结构进行了表征.结果表明,酸性条件下,壳聚糖的降解主要由.H和.OH自由基共同作用引起,加入H2O2或者通入N2O都能够略微提高.OH自由基浓度,对壳聚糖的降解有促进作用.加入异丙醇后,由于同时降低了.H和.OH自由基浓度,导致壳聚糖降解缓慢.当溶液的pH接近中性后,对壳聚糖的降解起主要作用的为.OH自由基,加入H2O2或者通入N2O都会增加.OH自由基的浓度,从而明显提高壳聚糖的降解速率.此外,研究发现低分子量的壳聚糖具有较快的降解速率.样品的UV、FTIR分析表明,辐照后除在壳聚糖分子链端生成羰基外,壳聚糖主链结构未见变化,脱乙酰度也没有显著改变,显示出辐射降解是一种有效的控制壳聚糖分子量方法.     

STABILIZATION OPTIMIZATION OF AQUEOUS MONOMER SOLUTIONS IN OIL EMULSIONS USING THE COHESIVE ENERGY RATIO CONCEPT.

The Beerbower-Hill approach based on the Cohesive Energy Ratio concept (CER) has been applied in order to optimize the stabilization of Acrylamide-water or Acrylic Acid (pure and 80% neutralized)- water mixtures in cyclohexane emulsions.

Using surface tension measurements for the determination of the solubility parameter of the aqueous phase ( δ_w), it was found that the presence and amount of the water-soluble monomer could be accounted for the evaluation of the optimal HLB.

Predictions were compared to experimental HLB values obtained by using various blends of a low-HLB emulsifier (a sorbitan monooleate named MONTANE 80) and high-HLB emulsifiers (either a nonylphenolpolyoxyethylene [40 EO] or a pOE [20 EO] sorbitan trioleate, MONTANOX 85).     

胆绿素在碱性水溶液中稳定性的极谱研究

胆绿素是人体内存在的重要胆色素之一，为线型叶啉结构，热敏性及光敏性较强，很不稳定，升温及光照均加速其氧化，使测定结果偏低。作者对胆绿素在碱性水溶液中的极谱行为进行了深入研究，试验了支持电解质、溶液酸度、溶液中溶解氧、光照及微量金属离子的存在等多种因素对胆绿素稳定性的影响，并研究了部分影响的作用机理。本文提出的极谱法测定胆绿素的最佳操作条件为：０．０４ｍｏｌ／ＬＮａ＿２ＨＰＯ＿４缓冲溶液为底液，ＰＨ值为１１，底液中加入４×１１￣（－４）／ＬＥＤＴＡ或通氮气１Ｏｍｉｎ，避光操作，测定在０．５ｈ内完成。     

浓环氧乙烷水溶液的选择性催化制乙二醇工艺研究

合成了苯乙烯型强碱阴离子交换树脂,将其用于环氧乙烷催化水合制乙二醇反应中,研究了温度、浓度、空速对树脂催化性能的影响,探讨了树脂的不可逆膨胀及失活原因.结果表明,在393K树脂发生降解,降解物与环氧乙烷反应生成聚乙二醇胺,导致树脂膨胀破裂;在温度353K,压力1.5MPa,液时空速0.2h-1下,环氧乙烷转化率100%,乙二醇的选择性96.3%,使用1600h后,催化剂的膨胀率6%,强碱容量损失率7.5%.     

ADSORPTION PROPERTIES OF THE STEARIC ACID-OCTADECANE PARTICLES IN AQUEOUS SOLUTIONS

The adsorption properties and surface charge creation for the stearic acid and octadecane/aqueous electrolyte solutions are considered. The hairy structure of surface charge for these systems was confirmed on the basis of potentiometric titration, ion adsorption and electrophoretic measurement data. For the system with stearic acid the reaction of ionization and complexation of carboxyl groups of stearic acid molecules from subsurface layer are responsible for the creation of surface charge and adsorption properties. The surface charge at octadecane particle is probably the results in adsorption and orientation of water molecules at the interface.     

氯苯类化合物在盐水溶液中的活度系数

在25.00±0.01 ℃下用紫外、可见分光光度法分别测定了氯苯(CB)、m-二氯苯(mDCB)、p-二氯苯(pDCB)、1,2,4-三氯苯(TCB)在NaCl、KCl、Na_2CO_3、K_2SO_4、CaCl_2盐水溶液及氯苯在Et_4NBr水溶液中的话度系数, 得出盐效应常数. 除Et_4NBr对氯苯呈盐溶作用, 其余均为盐析作用. 盐析次序大致为K_2SO_4>Na_2CO_3>CaCl_2>NaCl>KCl. 计算了盐效应常数的各种理论值, 与实验值进行比较, 进一步证实了改进后的内压力理论值更接近实际. 同时也讨论了这些数据在环保中的应用.     

QUENCHING OF PYRENE FLUORESCENCE BY TRYPTOPHAN IN MICELLAR SOLUTIONS

Deactivation of excited pyrene incorporated to cationic (cetyltrimethylammonium chloride), anionic (sodium dodecyl sulfate) and neutral (Triton X-100) micelles by tryptophan has been investigated over a wide pH range. Data obtained allow an estimation of the tryptophan association to the micelles, of the tryptophan apparent p K in the micellar solutions, and of the dynamics of tryptophan incorporation to the micellar pseudophase. In particular, the data obtained at pH 7 allow an estimation of the effect of the micellar charge upon the binding capacity of the tryptophan zwitterion.     

PHOTOIONIZATION OF TRYPTOPHAN: AN ELECTRON SPIN RESONANCE INVESTIGATION

The photoionization of tryptophan has been studied by ESR spectroscopy using the free radical scavenger 5, 5 dimethyl-1-pyrroline-l-oxide as a spin trap for hydrated electrons. A special set-up has been devised to irradiate more than one aliquot of the bubbled aqueous solutions in the cavity without removing the ESR cell out of the cavity.
Quantum yields of electrons production have been estimated as a function of irradiation wavelength. No photoionization threshold has been observed in these experiments.     

EFFECTS OF INDOLE AND TRYPTOPHAN ON FURAN OXIDATION BY SINGLET OXYGEN IN MICELLAR SOLUTIONS

Abstract— The 1,3-diphenylisobenzofuran oxidation by singlet oxygen was investigated in aqueous dode-cyltrimethylammonium chloride micellar solutions using pyrene as photosensitizer. It was found that indole and tryptophan markedly enhanced the furan oxidation in micellar solutions. This enhancement effect strongly depended on the ethanol content in micellar solutions; enhancement effect below about 0.3 mol fraction of ethanol and inhibition effect above this mole fraction. In the former ethanol range, a quenching of pyrene fluorescence by indole or tryptophan and a difference spectrum of furan between micellar solutions in the presence and absence of indole or tryptophan appeared strongly, but they were weakened in the latter ethanol range. The interactions between indole or tryptophan and pyrene and/or furan might be responsible for the enhancement effect observed. Discussion was made in connection with the micelle structure.     

脂肪酸钠盐对于苯甲酸在水中溶度的影响

在25°脂肪酸钠盐对正戊酸在水中溶度的影响是不规则的盐溶和盐析作用,其原因是排代出的新酸分布于正戊酸相和盐溶液相间^[1]。黄子卿等^[2]曾在25°研究脂肪酸盐(甲酸钠至戊酸钠)对正己酸在水中溶度的影响,除甲酸钠外,盐溶随盐的碳原子数目的增加而下降。Philip等^[3]曾在25°测定苯甲酸在甲酸钠和乙酸钠水溶液中的溶度。在本文中,作者测定在25°苯甲酸在五种脂肪酸钠(甲酸钠至戊酸钠)水溶液中的溶度。     

A NEW METHOD FOR THE DETECTION OF SINGLET OXYGEN IN AQUEOUS SOLUTIONS

Abstract— In experiments on the interception of reactive intermediates of strongly oxidizing character in dye (S) sensitized photooxidations using p -nitrosodimethylaniline (RNO) as a selective scavenger, it has been observed that some substrates (A) or ¹O₂ acceptors (like imidazole derivatives) induce the bleaching of RNO as followed spectrophotometrically at 440 nm. Since singlet oxygen (¹O₂) does not react chemically with RNO, this bleaching is a consequence of ¹O₂ capture by the imidazole ring which results in the formation of a trans-annular peroxide intermediate [¹O₂] capable of inducing the bleaching of RNO (-RNO). In the absence of RNO, [¹O₂] decomposes or rearranges into the final oxygenation product ¹O₂: ¹Δ_g Thus, the system imidazole plus RNO can be used as a sensitive and selective test for the presence of ¹O₂ in aqueous solutions. The method can also be applied in the presence of sensitizing dyes which, under visible irradiation, can partially bleach RNO even in the absence of imidazole derivatives. In such a case, the bleaching of RNO is strongly increased by the presence of imidazoles with a characteristic dependence on their concentration. The separation of the product of RNO bleaching by thin layer chromatography can serve as additional proof of the presence of ¹O₂ in the system. The imidazole plus RNO method has been applied to a number of sensitizing and non-sensitizing dyes.     

Zn在KOH水溶液中的阳极溶解和钝化机理

本文用旋转圆盘电极、稳态极化曲线、交流阻抗及恒电流充电曲线等方法研究了Zn在常温(30℃)和低温(-20℃)的KOH水溶液中阳极溶解和钝化过程的规律。从而提出其反应机理,并用最优化程序在TRS-80微型计算机上计算了反应机理中基元反应的速度和动力学参数的最佳值。由动力学参数计算的φ～i关系定量地符合从阳极溶解至钝化前整条极化曲线实验数据。旋转圆盘电极的转速效应、交流阻抗值以及恒电流充电电量值也都与提出的反应机理相符合。     

ELECTROCHEMICAL PROPERTIES OF ASPHALTENE PARTICLES IN AQUEOUS SOLUTIONS

The electrical properties of colloidal asphaltene/water solution interface were determined by carrying out the potentiometric titration and electrokinetic measurements. Asphaltenes in aqueous solutions exhibit typical organic colloid properties i.e. surface charge and electrophoretic mobility. It was considered that the surface charge at the asphaltene particles is a result of protonation and dissociation reactions of surface functional groups. On the base of the surface charge density data vs. pH the surface reaction constants were calculated by numerical method. The agreement of these values with calculated ones, on the base of ζ potential data, is noticeable.

The characteristic feature of the investigated systems is the maximum, appearing on the curve ζ potential vs. electrolyte concentration. This behaviour is explained by _”hair layer ” structure of the asphaltene surface     

FLASH PHOTOLYSIS OF AQUEOUS TRYPTOPHAN, ALANYL TRYPTOPHAN AND TRYPTOPHYL ALANINE

Abstract— Tryptophan has been flash photolysed in deoxygenated and air equilibrated solutions. The kinetics of the subsequent reactions of the tryptophyl radical and the hydrated electron have been elucidated. Oxygen has been found to reduce the primary photoionization yield, indicating a triplet state precursor, but no evidence has been found for a biphotonic process. Appreciable differences in the photoionization quantum yields have been found for tryptophan, alanyl tryptophan and tryptophyl alanine.     

荧光探针技术研究共溶剂对PEO-PPO-PEO嵌段共聚物溶液胶束的形成及内部结构的影响

选择了甲醇、乙醇、正丙醇、乙二醇、乙二胺、乙醇胺及２甲氧基乙醇等七种包括单官能团和双官能团共溶剂、与水组成混合溶剂,并利用荧光探针技术研究了共溶剂对环氧乙烷环氧丙烷环氧乙烷（ＰＥＯＰＰＯＰＥＯ）共聚物水溶液胶束形成及其结构的影响,结果表明,一些共溶剂与水和共聚物ＰＰＯ段都具有较好的混溶性,使形成胶束的ＣＭＴ升高,而其它共溶剂的引入则使得形成胶束的ＣＭＴ降低．从共溶剂对所形成胶束的微结构影响看,能与共聚物链有较强作用的双官能团的共溶剂和有较小分子尺寸的共溶剂有利于使形成的胶束具有较紧密的结构,在此条件下,形成胶束的紧密程度决定了胶束内微极性的大小,而与引入共溶剂的极性大小关系不大．     

STUDIES ON THE UV PHOTODESTRUCTION OF PURINE FREE BASE IN AQUEOUS SOLUTIONS AT 77 and 298K

Abstract— The photodestruction of purine free base used as a model for the purine bases in DNA has been studied in order to better understand the effect of UV light on these molecules. Photodestruction yields have been determined in glassy aqueous solutions at 77 K and at room temperature at different pH's. The yield decreases in the order of 0.04, 0.01, 0.001 in 8 M NaOH, 8 M NaCIO₄ and 6 M H₃PO₄, respectively, while at room temperature the highest destruction yield is 0.005 for the unbuffered neutral solution. These yields have been determined by measuring the initial decrease in the purine absorption maximum as a function of irradiation time. During the illumination stable photoproducts, as well as reactive intermediates, such as trapped electrons, radical anions and cations, are formed and have been characterized from their absorption spectra. The addition of triplet quenchers and an electron scavenger resulted in a decrease in the yield, implying the participation of the purine triplet state and a radical anion in the reactions leading to the photodestruction of purine.     

萘在1-1价小离子盐水溶液中活度系数的研究(V)

本文用紫外分光光度法测定了25 ℃下萘在LiBr、NaBr,KBr、NH_4Cl、NaF及KF盐水溶液中的活度系数f。将萘的lgf分别对六种盐的浓度c_S作图, 得到通过原点的直线, 符合Setschenow盐析公式, 直线斜率就是盐析常数k。本文还计算了萘在盐水溶液中盐析常数的各种理论值, 并对各种理论值进行对比, Debye-MacAulay理论和McDevit-Long公式的计算值都较实验值大2—3倍。Conway等人理论的计算k值对不同盐差别很小, 而实验值彼此之间的差别却很大。对体积大的非电解质, 色散力对盐析常数的影响不可忽略。本文对Bockris公式进行修正, 计算结果表明, 它能较正确地指出盐效应的次序及盐析常数的符号。内压力理论改进公式的计算结果不仅能预言盐析常数的符号, 也能指出盐析常数大小的顺序, 理论值与实经值符合较好。