The effect of phospholipase D on the function of fragmented sarcoplasmic reticulum

Incubations of fresh preparations of fragmented sarcoplasmic reticulum (FSR) were carried out at pH 5.7. This pH was necessary for hydrolysis of phospholipids by phospholipase D. The pH did not influence calcium uptake or the activity of calcium-stimulated ATPase of FSR. Treatment of FSR with phospholipase D caused hydrolysis of the membrane phospholipids. The phosphatidic acid produced remained bound to the membrane. Increasing phospholipid cleavage was paralleled by loss of calcium uptake, which was complete when about two-thirds of the membrane phospholipids were hydrolyzed.     

pH条件对二种家蚕丝素蛋白铁元素螯合量的影响

以水解丝素蛋白及中性盐解蛋白螯合微最金属元素铁,通过螯合液pH值的调节可以控制丝素蛋白与铁的螯合量.酸性条件下,随着pH值的上升,螯合量增加;但在碱性条件下,螯合量反而下降.铁元素螯合量的增加使丝素蛋白的分子结构趋向于无规则卷曲构造.     

Enzymatic hydrolysis of 1-monoacyl-SN-glycerol-3-phosphorylcholine (1-lysolecithin) by phospholipases from peanut seeds

Hydrolysis of 1-lysolecithin (1-acyl glycerophosphorylcholine [1-acyl GPC]) by preparations of phospholipase D from peanut seeds was investigated. 1-Lysolecithin was hydrolyzed at a much slower rate than phosphatidylcholine (lecithin). Although Ca⁺² ions are required for the cleavage of lecithin by the enzyme, their effect on the hydrolysis of lysolecithin depended upon the concentrations of the substrate: at 0.2 mM 1-lysolecithin, Ca⁺² ions increased the reaction rates, whereas at concentrations of the substrate lower than 0.1 mM, Ca⁺² ions were inhibitory. A broad pH activity curve between 5 and 8 was obtained with higher rates in the alkaline range, both in the absence and presence of Ca⁺² ions. The increased hydrolysis of lysolecithin due to Ca⁺² was noticed over the entire pH range. Upon storage of the enzyme solutions at 4 C, decreased rates of hydrolysis of lecithin were observed, with t 1/2 values of ca. 50 and 100 days depending on the purity of the preparation. During the same period, no reduction occurred in the activity of these preparations on lysolecithin as substrate. The effects of Ca⁺² ions and the analysis of the products of 1-acyl GPC cleavage by the enzyme preparations revealed by the enzyme preparations revealed the presence of more than one enzyme and the formation of the following compounds: lysophosphatidic acids (1 acyl glycerophosphoric acids), free fatty acids, glycerophosphorylcholine, and choline. The possible pathways leading to the degradation of lysolecithin and the formation of these products include reactions catalyzed by lysophospholipase A₁ (lysophosphatidylcholine 1-acyl hydrolase, E.C. 3.1.1.5) and a phosphodiesterase (L-3-glycerylphosphorylcholine glycerophosphohydrolase, E.C. 3.1.4.2), in addition to phospholipase D (phosphatidylcholine phosphatidohydrolase, E.C. 3.1.4.4).     

阳离子松香中性施胶剂

以松香、环氧氯丙烷及三乙胺为原料，按照物质的量比１∶０－７∶０－７ 投料，搅拌下恒温９０℃回流４ ～６ｈ，合成出自身阳离子型的松香胶（ＳＣＲ） 。将上述胶料在强烈机械搅拌下加水及其它辅助助剂配成质量分数为１％ 的白色乳液，用电泳法测其在ｐＨ 值为４ ～９ 时的Ｚｅｔａ 电位值，波动范围均在＋ ２５ｍＶ～＋５２ｍＶ之间。同一乳液在中、碱性条件下（ｐＨ＝６～９） ，Ｚｅｔａ 电位几乎为恒定值且略高于酸性条件下的Ｚｅｔａ 电位，因此ＳＣＲ胶料更适于用作中性及弱碱性条件下的纸张施胶剂。杂质盐ＣａＣｌ２ 、ＭｇＣｌ２ 会明显降低ＳＣＲ胶料的Ｚｅｔａ 电位。造纸业中常用的ＣａＣＯ３ 填料也会使ＳＣＲ胶料的Ｚｅｔａ 电位略有降低，但变化并不明显。分别添加含有少量ＣａＣｌ２ 、ＭｇＣｌ２ 及ＣａＣＯ３ 的胶料乳液到纤维悬浮液中，控制体系的ｐＨ值为６－５ ～８－５，胶料在纤维上的吸附显微照片显示，在此条件下胶料均可以在纤维上较好地吸附。     

Studies on free and immobilized lipases fromMucor miehei

An extracellular lipase produced by fermentation with a selected strain ofMucor miehei has been purified partially in two forms: A and B. The forms have a high degree of antigenic identity and have similar pH-activity profiles with tributyroylglycerol as the substrate with optima at pH 7. The differences are A, in contrast to B, requires activation at alkaline pH before analysis; A binds with concanavalin A more completely than B, the net charges are slightly different at pH 8; the isoelectric points are different. Our results indicate that the B lipase is formed by partial deglycosylation of the A lipase and that this influences the activity toward emulsions. The two enzymes have been immobilized by adsorption. These preparations and the soluble forms were highly specific for primary ester of triacylglycerols (TG), usually hydrolyzed TG of 12:0, 14:0, 16:0 and 18:1 more rapidly than those of 4:0, 6:0, 8:0 and 10:0 in mixtures of monoacid TG (4:0 to 18:1), and were not stereospecific for TG. Immobilization altered the specificity of the preparations somewhat in that slightly more 14:0 and 16:0 were released. Presented at the symposium “The Biology, Biochemistry and Technology of Lipases” at the 78th annual meeting of the American Oil Chemists’ Society held May 17–21, 1987, in New Orleans, Louisiana.     

Promotion of Attack on Glass and Silica by Citrate and Other Anions in Neutral Solution

The observation that essentially neutral solutions of sodium citrate attacked sulfur-treated soda-lime glass bottles of generally high chemical resistance much more than was anticipated led to a general investigation. It has been found that neutral solutions of sodium citrate attack silicate glasses and silica with a severity similar to that of substantially alkaline solutions. This effect was observed for both soda-lime and borosilicate glasses and also for vitreous, crystalline, and amorphous forms of silica. The effect of citrate becomes perceptible at a pH of about 5 and increases rapidly with pH up to 7.6. Solutions of higher pH were not studied. Solutions of certain other complex-forming anions show the effect on sulfur-treated soda-lime glass containers in varying lesser degrees. Although the active anions studied are complexing agents for alkaline earths and aluminum, it was observed that citrate had more action on a fused silica container than on containers made of certain glasses containing calcium and aluminum. Therefore a digestive action on silica and the Si–O–Si structure of glasses is to be recognized. Fluoride, the only anion tested that forms previously known complexes with silicon, had slightly less action on sulfur-treated bottles than citrate. The results suggest that soluble silicon complexes are formed at pH values in the region of 7 by citrate and some of the other organic anions studied.     

Partial purification and characterization of free and immobilized lipases fromMucor miehei

An extracellular lipase, a glycoprotein, produced by fermentation with a selected strain ofMucor miehei has been partially purified in two forms, A and B. The two forms have a high degree of antigenic identity and have similar pH-activity profiles with tributyroylglycerol as a substrate with optima at pH 7. They differ as follows: A, in contrast to B, requires activation at alkaline pH before analysis; A binds with concanavalin-A more completely than B; the net charges are slightly different at pH 8; and the isoelectric points are different. Our results indicate that the B lipase is formed by partial deglycosylation of the A lipase and that this influences the activity toward emulsions. In addition, the two enzymes have been immobilized by adsorption. These preparations and the soluble forms were highly specific for primary esters of triacylglycerols (TG); they usually hydrolyzed TG of 12∶0, 14∶0, 16∶0, and 18∶1 more rapidly than those of 4∶0, 6∶0, and 8∶0 and 10∶0 in mixtures of monoacid TG (4∶0 to 18∶1); and they were not stereospecific for TG. Immobilization altered the specificity of the preparations somewhat, in that slightly more 14∶0 and 16∶0 were released. Scientific Contribution No. 1192, Storrs Agricultural Experiment Station, University of Connecticut, Storrs, Connecticut.     

Long chain fatty acid methyl ester hydrolase activity in mammalian cells

Long chain fatty acid methyl esters were hydrolyzed by cell free homogenates and subcellular fractions prepared from Ehrlich ascites tumor cells. The highest enzyme specific activity was observed in the microsomal fraction. Maximum hydrolase activity occurred in the pH range of 6.5–7.0. The relative activities for the methyl ester substrates that we tested were: methyl palmitate > methyl laurate > methyl oleate > methyl stea-rate. Butyl palmitate also was hydrolyzed by this enzyme. Enzymatic activity increased when the methyl ester-albumin complex concentration or the methyl ester-albumin molar ratio was raised. In addition to Ehrlich cells, methyl ester hydrolase activity was observed in homogenates of rat heart and liver. The highest enzyme specific activities also occurred in the microsomal fractions prepared from these tissues. Research Career Development Awardee of the National Heart and Lung Institute (K4-HE-20,338).     

磷脂对浓缩天然胶乳机械稳定性的影响

在天然胶乳中添加磷脂,研究磷脂对天然胶乳机械稳定性的影响,结果表明,随着磷脂用量和氨含量的增加,天然胶乳的机械稳定度逐渐升高。气相色谱-质谱联用仪(GC-MS)分析表明,磷脂在碱性条件下水解产生亚油酸、棕榈酸、油酸、反油酸、硬脂酸、α-亚麻酸等长链脂肪酸,进一步与氨水反应形成脂肪酸铵,并吸附在橡胶烃粒子表面,提高了天然胶乳的机械稳定性。随着碱度的升高和水解时间的延长,磷脂水解产物的化学组成和含量存在一定差异。     

Electrochemical Oxidation of Phenol on Metal‐Impregnated Zeolite Electrodes

Nanodispersed metallic clusters of platinum, silver and cobalt were incorporated into NaX zeolite cavities by impregnation with acetone solution of corresponding acetylacetonates and solvent evaporation followed by acetylacetonate thermal decomposition. The mixture of modified zeolites and 10 wt % of carbon black, in the form of a thin layer, was pasted onto a glassy carbon surface by Nafion. With such electrode materials, the phenol oxidation in neutral, alkaline and acid solution was studied by cyclovoltammetry. Deactivation of all electrodes in both neutral and alkaline medium was observed, indicating that polymerization reaction might be the main reaction pathway of phenol at higher pH values. Formation of quinine‐type structures was obtained during electro‐oxidation at lower pH values, being more significant in acidic solutions.     

新型罗丹明类荧光标记探针的研究(Ⅰ)--氨基标记产物的质子化互变异构

罗丹明B-N-琥珀酰亚胺酯可用于生命体系物质氨基标记的新型荧光探针。研究了标记产物在不同的pH介质中的紫外一可见及荧光光谱特性，结合质子化互变异构机理，对互变异构现象与光谱变化的相关性进行了考察，确认了仲酰胺在中性和碱性条件下形成无荧光性的螺环内酰胺结构。     

不同pH的三聚氰胺水溶液溶解性能研究

测定三聚氰胺在不同酸度水中的溶解度,并用二参数简化的溶解度方程对实验数据进行了关联.结果表明,在不同温度下,三聚氰胺在弱酸性条件下溶解度大于中性和碱性条件下的溶解度,碱性条件下它的溶解度大于中性条件下的溶解度.在不同酸度下,三聚氰胺的溶解度随温度升高而升高;在强酸和强碱条件下,溶解度随酸性和碱性增加而增大.     

Influence of the pH on Distribution of Denim Blue in Water Fe-Zeolitic Tuff System

In the present study, the processes of adsorption of denim blue by Fe-zeolitic tuff from aqueous solutions at different pH values were determined. The parameters, K_d(n), K_d(i), Φ_n, pK_a were accurately predicted by applying the linear model to sorption isotherms at different pH values of denim blue. Maximum removal of denim blue was observed at pH values between 3 and 5, where neutral species are the main components of the solution. The results indicate that pH has a pronounced effect on denim blue sorption depending on the conditions of the system.     

Electrodeposition of CoWP film: III. Effect of pH and temperature

Polarisation behaviour and nucleation mechanism of induced co-deposition of cobalt, tungsten and phosphorus from citrate electrolytes containing cobalt sulphate, sodium tungstate and sodium hypophosphite on copper disc electrode at various electrolyte pH values were studied using cyclic voltammetry and chronoamperometry, respectively. It was found that the onset potentials for reduction and oxidation gradually shifted towards more cathodic direction with increase in pH. Co-deposition of cobalt, tungsten and phosphorus occurred under diffusion control and followed instantaneous type of nucleation mechanism. The highest current efficiency (>70%) was found when the CoWP films were deposited from neutral or slightly acidic solution. Larger variation of film composition, cobalt from 48 to 74 at.%, tungsten from 13 to 38 at.% and phosphorus from 8 to 33 at.%, could be made by changing the pH of the electrolyte between 3 and 8. The films deposited from very acidic solutions contained larger amounts of tungsten and phosphorus and were amorphous; while the films deposited from near neutral solutions were polycrystalline and contained hexagonal cobalt. The surfaces of the amorphous films were smoother than those of the polycrystalline films. Needle-like dendritic crystallites were obtained when the films were deposited from basic solution or at elevated temperature.     

Hydrolysis of neutral lipid substrates by rat hepatic lipase

Rat hepatic lipase, an enzyme whose involvement in the catabolism of lipoproteins remains poorly defined, has both neutral lipid and phospholipid hydrolyzing activity. We determined the substrate specificity of hepatic lipase for 1-oleoyl-sn-glycerol, 1,2-dioleoyl-sn-glycerol, and 1,3-dioleoyl-sn-glycerol in the Triton X-100 mixed micellar state, and compared these results to those obtained previously in our laboratory for the phospholipid substrates phosphatidic acid (PA), phosphatidylethanolamine (PE), and phosphatidylcholine (PC). V_max values were determined by diluting the substrate concentration in the surface of the micelle by Triton X-100. The V_max values obtained were 144 μmol/min/mg for 1-oleoyl-sn-glycerol, 163 μmol/min/mg for 1,2-dioleoyl-sn-glycerol, and 145 μmol/min/mg for 1,3-dioleoyl-sn-glycerol. These values were higher than those obtained earlier for phospholipids which were 67 μmol/min/mg for PA, 50 μmol/min/mg for PE and 4 μmol/min/mg for PC. In addition, the mole fraction of lipid substrate at half maximal velocity (K) in the surface dilution plot was lower for the neutral lipid substrates as compared to those obtained for the phospholipid substrates. When the hydrolysis of 1,3-dioleoyl-sn-glycerol mixed micelles was studied as a function of time, cleavage at thesn-1 andsn-3 positions occurred at the same rate, suggesting that hepatic lipase is not stereo-selective with respect to 1,3-diacyl-sn-glycerol substrates. To determine if the presence of one lipid could affect the hydrolysis of the other, all possible dual combinations of 1-oleoyl-sn-glycerol, 1,2-dioleoyl-sn-glycerol, and 1,3-dioleoyl-sn-glycerol, in the same micelle were made and the hydrolysis rate of each substrate was determined. Interaction occurred only for the 1,2-dioleoyl-sn-glycerol/1,3-dioleoyl-sn-glycerol mixture where the hydrolysis of 1,2-dioleoyl-sn-glycerol was slightly inhibited and that of 1,3-dioleoyl-sn-glycerol slightly activated compared to the predicted theoretical rate. These findings demonstrate that when presented in similar physical states, the neutral lipid substrates tested were hydrolyzed at a higher rate by hepatic lipase than the phospholipid substrates.     

Surface hydrolysis of postconsumer polyethylene terephthalate to produce adsorbents for cationic contaminants

In this work, the surface hydrolysis of postconsumer polyethylene terephthalate (PET) was used to produce an ion exchange material to adsorb cationic contaminants from water. The PET surface hydrolyses were carried out in neutral, alkaline, and acid media (NaOH or HNO₃ at 7, 10, and 15 mol L^?1) under reflux producing surface carboxylic acid sites (? COOH) characterized by ATR‐IR, pyridine adsorption, titration, TG, and DSC analyses. Acid hydrolysis produced high concentrations of ? COOH (up to 0.5 mmol g^?1_PET), whereas no significant concentration of carboxylic acid sites was obtained by neutral and alkaline hydrolysis. SEM analyses suggest that the acid sites are likely located at the cracks and defects produced on the PET surface by acid hydrolysis. Neutral or alkaline hydrolysis produced a very regular and smooth PET surface with very low acid site concentrations. The adsorption isotherms of Cd⁺² as a model of heavy metal and the dye methylene blue as a model of large organic cationic molecules showed high adsorption capacities for the HNO₃‐hydrolyzed PET, whereas no adsorption takes place on the neutral‐ or alkaline‐hydrolyzed polymer. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 5284–5291, 2006     

New detergent mechanism using cellulase revealed by change in physicochemical properties of cellulose

Sebum in naturally soiled cotton undershirt and oleic acid in artificially soiled cotton cloth, which entered interfiber space in the interior of cotton fibers were easily removed by alkaline cellulase fromBacillus sp., but only with difficulty by commonly used detergent ingredients such as surfactant and protease. Adsorption isotherms and the rate of hydrolysis of alkaline cellulase against insoluble cellulose powders revealed that the lower the relative crystallinity of cellulose powder, the more adsorptive alkaline cellulase became and the more hydrolysis was promoted. With alkaline cellulase, cotton having the highest relative crystallinity was adsorbed at pH 9 and 5°C, liberated a negligible small amount of reducing sugar at pH 9 and 40°C, and produced no changes in the degree of polymerization of cotton cellulose and in the tensile strength of cotton fabric at pH 9 and 30°C. On the other hand, differential scanning calorimetric studies revealed that under similar conditions even a small quantity of alkaline cellulase drastically reduced the amount of water bound to cellulose in cotton. Because water was bound only with hydroxy groups of cellulose molecules in the amorphous region of cotton fibers, it can be understood that soil entering the interfiber space of amorphous interlamellae in the interior of cotton fibers, was easily removed as the hydrated cellulose in the interlamellae was slightly hydrolyzed by alkaline cellulase. A new detergent mechanism is proposed.     

化妆品基础环境对β-熊果苷稳定性的影响

熊果苷是美白和祛斑作用的化妆品中最为广泛使用的美白剂之一。选取β-熊果苷为研究对象,改变化妆品的温度和pH值,对β-熊果苷的稳定性进行讨论。同时,采用紫外分光光度法测定β-熊果苷在不同浓度和不同基础环境下分解产物含量。实验结果表明,温度为30℃~40℃,质量分数为0.2%~1.0%时,β-熊果苷相对稳定。反应温度高于50℃时,β-熊果苷溶液的分解趋势曲线陡增,可分析50℃为β-熊果苷的极限分解温度;β-熊果苷在中性及偏酸性的pH条件下相对稳定,在酸性(pH4)或碱性(pH9)的环境下易分解。并由此进一步确定适用于美白和祛斑类化妆品的体系的温度和酸碱度。     

Adsorption of trivalent chromium from aqueous solutions onto activated carbon

The adsorption of chromium (III) onto activated carbon was investigated as a possible alternative method for its removal from aqueous solutions. The adsorption data were obtained in a batch adsorber and fitted the Langmuir adsorption isotherm well. The effect of pH on the adsorption isotherm was investigated at pH values of 2, 4, 5 and 6. It was found that at pH values below 2 the Cr(III) was not adsorbed and at pH values above 6.4 the Cr(III) was precipitated as Cr(OH)₃. Maximum adsorption occurred at pH 5. The pH plays a very important role in the adsorption of Cr(III) since Cr(III) can form different complexes in aqueous solutions. The adsorption capacity was increased by about 20% as the temperature was raised from 25 to 40°C. It was concluded that Cr(III) is adsorbed to an appreciable extent on activated carbon and that the adsorption is highly dependent upon pH.     

添加剂对有机颜料光催化降解的影响

本文研究了添加(NH4)2S2O8,H2O2以及表面活性剂十二烷基苯磺酸钠(DBS)时,对TiO2光催化降解颜料艳红6B的影响。(NH4)2S2O8的加入可提高水溶性差的颜料艳红6B的降解速度,以酸性及中性条件较适宜。H2O2的加入可提高6B的降解速度,并且TiO2／UV／H2O2要比TiO2／UV或者H2O2／UV体系有效得多,可提高TiO2的重复使用次数及H2O2的利用率。阴离子型表面活性剂DBS的加入降低了6B的降解速度,但在酸性和碱性条件下,6B的降解较中性条件快;DBS的降解在中性条件下较好;二者存在密切的共降解关系。随着表面活性剂DBS浓度的增加,颜料艳红6B和DBS的降解速率均减慢