醇/盐双水相体系中α-环己基扁桃酸手性分子识别

以含羟丙基-β-环糊精（HP-β-CD）手性识别剂的醇/盐双水相体系作为一种新型的手性识别萃取体系,研究了α-环己基扁桃酸(CHMA)对映体在其中的手性识别行为.详细考察了HP-β-CD浓度、CHMA浓度、乙醇和硫酸铵质量分数、体系温度和pH值等因素对CHMA对映体分配比（D）和分离因子(α)的影响.结果显示,含有手性识别剂HP-β-CD的乙醇∕硫酸铵双水相体系对CHMA对映体具有很强的手性识别能力;体系中HP-β-CD浓度、乙醇质量分数、温度和pH值等因素对对映体的分离度影响较大;在体系温度为40 ℃,pH值为2,乙醇质量分数为30%,硫酸铵质量分数为15%,HP-β-CD的浓度为50 g.L-1,CHMA浓度为0.5 mmol.L-1时,手性识别分离效果最佳,分离因子（α）达到了1.86.     

离子液体双水相萃取山楂黄酮和多糖的相行为研究

用分光度法研究了[Bmim]BF4/(NH4)2SO4双水相体系萃取山楂黄酮和多糖的相行为,考察了同时提取这两种组分时[Bmim]BF4的浓度、(NH4)2SO4的浓度、山楂的用量、超声萃取时间等因素对双水相的上下相体积以及分配系数的影响。结果表明:(1)离子液体浓度的增加,双水相的上、下相体积分别明显增大和减小。但黄酮和多糖在双水相中的分配系数仅有波动,均小于5%;(2)硫酸铵浓度的增加,双水相的上下相体积分别明显减小和增大。同时黄酮和多糖的分配系数均有较明显先降低后升高的趋势;(3)山楂质量的增减,不影响双水相的形成,但存在一个实验条件下的溶出饱和值,该值为0.15g,此时黄酮和多糖的分配系数最大;(4)超声萃取时间的延长或缩短,同样不影响双水相的形成,但存在对山楂有效成分达到饱和溶出的阈值,对于黄酮为25min,多糖为20min。     

PEG-无机盐双水相体系萃取水榆花楸叶中总黄酮

水榆花楸叶中所含的黄酮类化合物具有一定的药用价值,利用双水相技术萃取水榆花楸叶中的黄酮是一种有效的分离纯化方法。本文考察了不同种类的无机盐与不同相对分子量的PEG组成的双水相体系的两相性质,研究了PEG1000-Na_2SO_4双水相体系中分离纯化水榆花楸黄酮时PEG的质量分数、Na_2SO_4的质量分数、温度、p H、KCl添加量这5个因素对分配行为的影响,并通过正交实验优化了试验条件。结果表明最佳双水相萃取条件为:Na_2SO_4的质量分数为15%,PEG1000质量分数为30%,p H为9,提取温度为25℃,KCl的添加量为3%,此时原料中黄酮的萃取率可高达97.01%。因此,该体系是一种高效分离纯化水榆花楸叶中黄酮的方法。     

双水相手性萃取拆分扁桃酸外消旋体

研究了扁桃酸(MA)对映体在含β-环糊精(β-CD)手性选择剂的聚乙二醇(PEG)/(NH_4)_2SO_4双水相体系中的萃取分配行为.考察了pH、PEG和(NH_4)_2SO_4的质量分数、β-CD的浓度、MA的浓度与萃取温度等因素对拆分效果的影响.实验结果表明:双水相手性萃取具有很强的手性分离能力,β-CD对L-MA对映体的识别能力大于对D-MA对映体的识别能力;当温度为30℃、pH=1.0、PEG2000质量分数为30%、(NH_4)_2SO_4质量分数为20%、β-CD的浓度为0.008 mol/L、扁桃酸的浓度为0.05 mol/L时,分离因子(α)达到2.46,上、下相对映体过剩值(e.e.%)分别为42.13%和40.43%.     

聚丙二醇-硫酸铵双水相萃取银杏黄酮

研究了银杏叶黄酮在聚丙二醇(PPG)400-(NH_4)_2SO_4双水相体系中的分配情况。探讨了单因素p H、PPG400质量分数、(NH_4)_2SO_4质量分数、料液比、温度、萃取时间对萃取率(Y%)和分配系数(K)的影响,并通过正交试验进一步优化双水相萃取条件。结果表明,各个因素对Y%和K影响为PPG400质量分数pH(NH_4)_2SO_4质量分数萃取时间萃取温度料液比。最佳萃取条件为p H 6、PPG400质量分数25%、(NH_4)_2SO_4质量分数15%、料液比1∶15、萃取温度40℃、萃取时间60min,黄酮萃取率达到98%以上。PPG400-(NH_4)_2SO_4双水相体系对银杏叶黄酮有较好的萃取效果。     

三嵌段共聚物EO20PO70EO20相分离行为的耗散粒子动力学模拟

采用耗散粒子动力学(DPD)方法研究了嵌段共聚物EO₂₀PO₇₀EO₂₀(P123)在水、乙醇/水溶液及二氧化硅溶胶体系中的相分离行为. 不同质量分数的P123在水溶液中共形成4种相分离状态: 球状胶束(10%); 椭球胶束(20%)、棒状胶束(30%)和三维立方胶束(50%). 在模板剂质量分数为10%的乙醇/水溶液中, 模板剂胶束稳定性随着乙醇含量的增加而变差. 在二氧化硅溶胶体系中, 模板剂质量分数低于5%时无胶束形成; 模板剂质量分数增至10%时, P123发生相分离形成三维球状胶束; 随着模板剂质量分数的进一步增加, 模板剂分子夹含着水分子形成三维椭球状结构(20%)、三维立方结构(40%)和层状结构(60%). 模拟结果与实验结果一致, 说明DPD模拟可以从计算角度推测模板剂对介孔材料结构的影响.     

基于离子液体-双水相体系同时测定蜂蜜中3种三嗪类除草剂残留

采用胆碱离子液体与非离子表面活性剂Triton x-100(Tr)建立环境友好的双水相体系(ABS),用于萃取蜂蜜中的西玛津、氰草津和阿特拉津3种三嗪类除草剂,并结合高效液相色谱法(HPLC)对除草剂残留进行测定。考察了相组成和温度对ABS形成的影响,结果表明离子液体中阴离子的碳链越长,ABS的双相区越小,而温度对ABS的双相区无显著影响。采用Tr-醋酸胆碱([Ch][Ac])双水相体系对待测除草剂的分配行为进行研究,发现待测组分主要富集于表面活性剂相。除草剂的分配系数随着Tr质量分数的增加而降低,而随着[Ch][Ac]质量分数的增加而增加,表明离子液体的盐析能力对双水相体系的形成起主导作用。在优化的萃取条件下,待测组分的线性范围为0. 1～20. 0 mg/L,相关系数(r~2)不低于0. 992,定量下限为0. 005～0. 02 mg/kg,平均加标回收率为75. 0%～114%,相对标准偏差为5. 2%～7. 6%。该方法适用于蜂蜜样品中此3种除草剂残留的分析。     

芯片毛细管电泳分离多种FITC衍生的氨基酸

用芯片毛细管电泳激光诱导荧光检测系统研究了分离多种荧光素异硫氰酸酯(FITC)衍生氨基酸的实验条件.采用以乙醇为有机添加剂的胶束毛细管电动色谱分离体系(50 mmol/LSDS,体积分数为15%的乙醇,5 mmol/L pH 9.2的硼砂缓冲液),在72 mm长的通道上实现了10种常见氨基酸的分离,一次分离的时间小于5 min.     

三辛基甲基氯化铵萃取色氨酸的影响因素

研究了水相离子强度、无机盐类型、萃取剂浓度、水相初始 pH0 值对色氨酸在三辛基甲基氯化铵(TOMAC) /正辛烷体系中分配行为的影响。实验结果表明 ,色氨酸的分配系数随着离子强度的增加而降低 ,但是当离子强度增大到一定程度时变化趋于平缓 ;分析了由于离子强度的影响而使实际过程的分配系数与理想过程分配系数不同的原因 ,得出了离子强度与活度系数的关系式 ;在萃取过程中增加有机相萃取剂浓度可提高两相间的分配系数DA;提高水相 pH0 值能提高色氨酸在两相间的分配系数DA,但当 pH0 >11时 ,对分配系数的影响很小 ;阳离子均为Na+ 情况下 ,DCl- >DBr- ;阴离子均为Cl-时 ,DNa+ >DK+ 。     

酶法合成L-4-甲砜基苯丙氨酸

以4-甲砜基苯丙酮酸和L-天冬氨酸为底物, 利用重组大肠杆菌DM204(pGEX-KG-aspC/BL21)表达的天冬氨酸转氨酶酶法转化得到了L-4-甲砜基苯丙氨酸, 优化得到的酶法最佳转化条件为: 转化温度37 ℃, 反应体系pH=8, 底物4-甲砜基苯丙酮酸质量分数8%, 质量分数0.6%的吐温80和10-4 mol/L Mg2+对酶活有促进作用. 在最佳工艺条件下经过12 h酶促反应, 4-甲砜基苯丙酮酸摩尔转化率达95%. 本研究利用化学生物法制备了L-4-甲砜基苯丙氨酸, 为制备其它天然氨基酸衍生物提供了新思路.     

Partitioning behavior of amino acids in aqueous two-phase systems containing polyethylene glycol and phosphate buffer

The partitioning behavior of four amino acids, cysteine, phenylalanine, methionine, and lysine in 15 aqueous two-phase systems (ATPSs) with different polyethylene glycol (PEG) molecular weights and phosphate buffers has been studied in the present paper. The phase diagrams of the systems are investigated together with the effect of the PEG molecular weight and pH of the phosphate solutions. The composition of these systems and some parameters such as density and refractive index are determined. The influences of salts in ATPSs, side chain structure of the amino acids, pH of ATPSs, and the PEG molecular weight on the distribution ratios of the amino acids have been studied. This work is useful for the purification of amino acids and the separation of some proteins whose main surface exposed amino acid residues are these four amino acids, respectively.     

Purification of salvianolic acid B from the crude extract of Salvia miltiorrhiza with hydrophilic organic/salt-containing aqueous two-phase system by counter-current chromatography

Establishment of hydrophilic organic/salt-containing aqueous two-phase system and purification of salvianolic acid B from crude extract of S. miltiorrhiza by counter-current chromatography with said system were studied. Ethanol and n-propanol were selected to constitute biphasic systems with ammonia sulphate, sodium chloride and phosphate separately, and related system characteristics including phase diagrams, phase ratio, separation time were tested. The partition coefficient of crude salvianolic acid B was also tested in above systems and further finely adjusted by altering the constitution of phosphate in n-propanol/phosphate system. Salvianolic acid B was purified to 95.5% purity by counter-current chromatography in 36% (w/w) n-propanol/8% (w/w) phosphate system with the ratio between dipotassium hydrogen phosphate and sodium dihydrogen phosphate of 94:6. One hundred and eight milligrams of salvianolic acid B was purified from 285 mg crude extract with the recovery of 89%.     

Simultaneous determination of several amino acids, including homocysteine, cysteine and glutamic acid, in human plasma by isocratic reversed-phase high-performance liquid chromatography with fluorimetric detection

A method for the simultaneous measurement of two biologically important thiol compounds cysteine and homocysteine and five amino acids including neurotransmitters aspartate and glutamate is reported. This method utilized derivatization of compounds with o-phthalaldehyde in the presence of 2-mercaptoethanol following alkylation of the free sulfydryl group with iodoacetic acid followed by separation using reversed-phase high-performance liquid chromatography. These o-phthalaldehyde-2-mercaptoethanol-labeled compounds were separated within 30 min on a Spherisorb ODS-2 column with isocratic elution using 17% methanol, 0.04 M sodium phosphate buffer (pH 7.0), 0.002 M Na2EDTA and detected fluorimetrically (excitation 340 nm, emission 450 nm). Using this method, the concentrations of homocysteine, cysteine, glutamic acid. aspartic acid, asparagine, serine and glutamine in human plasma were determined.     

Effect of nutrient supplements addition on ethanol production from cheese whey usingCandida pseudotropicalis under batch condition

Candida pseudotropicalis ATCC 8619 was selected among nine strains of lactose fermenting yeast for the production of ethanol from cheese whey. The effects of three nutrients (ammonium sulfate (NH₄)₂SO₄, dipotassium hydrogen phosphate K₂HPO₄, yeast extract, and a combination of them) on the ethanol yield from cheese whey were investigated. The results indicated that no addition of nutrient supplement is necessary to achieve complete lactose utilization during the cheese whey ethanol fermentation. However, addition of a small concentration (0.005% w/v) of these supplements reduced the lag period and the total fermentation time and increased the specific growth rate of the yeast. Higher concentrations (0.01 and 0.015% w/v) of ammonium sulfate and dipotassium hydrogen phosphate inhibited the cell growth and reduced lactose consumption. The highest ethanol (21.17 g/L) was achieved using yeast extract at a concentration of 0.01% w/v, given a conversion efficiency of 98.3%. No indication of alcohol inhibition was observed in this study.     

N-(5-氯-2-羟苯基)氨基酸酯的合成、表征及抑菌活性

以5-Cl水杨醛和L-苯丙氨酸、L-亮氨酸及L-甘氨酸的脂肪酸酯为原料,通过碱催化的席夫碱缩合反应,合成了6种N-（5-氯-2-羟苄基）席夫碱氨基酸酯及其还原产物N-（5-氯-2-羟苄基）氨基酸酯。 化合物的结构及组成经过IR、¹H NMR和元素分析测试技术进行了表征。 合成的席夫碱及其还原产物对革兰氏阴性菌、革兰氏阳性菌及真菌均有不同程度的抑制作用。 质量分数为0.01%的N-（5-氯-2-羟苄基）席夫碱氨基酸酯对大肠杆菌的抑菌率达90%以上,而N-（5-氯-2-羟苄基）氨基酸酯对金黄色葡萄球菌的抑菌率也在90%以上,均为强抑菌活性,其中N-（5-氯-2-羟苄基）苯丙氨酸酯的抑菌率达98%以上。     

Amino acid adsorption on mesoporous materials: influence of types of amino acids, modification of mesoporous materials, and solution conditions

In order to disclose the dominant interfacial interaction between amino acids and ordered mesoporous materials, the adsorption behaviors of five amino acids on four mesoporous materials were investigated in aqueous solutions with adjustable amino acid concentration, ion strength, and pH. The selected amino acids were acidic amino acid glutamic acid (Glu), basic amino acid arginine (Arg), and neutral amino acids phenylalanine (Phe), leucine (Leu), and alanine (Ala), and the selected mesoporous materials were SBA-15, Al-SBA-15, CH3(10%)-SBA-15, and CH3(20%)-SBA-15. The adsorption capacities of Glu and Arg were strongly dependent on pH and surface charge of the mesoporous adsorbent. The adsorption of Phe showed pH insensitivity but depended on the surface organic functionalization of mesoporous adsorbent. On the basis of the theoretical analysis about the interaction between amino acid and adsorbent, such a remarkable difference was attributed to the different nature of the interaction between amino acid and adsorbent. Arg could be readily adsorbed on the surface of SBA-15, especially Al-SBA-15, under appropriate pH in which the electrostatic interaction was predominant. The driving force of Phe adsorption on mesoporous adsorbent mainly came from the hydrophobic interaction. Therefore, the adsorption capability of Arg decreased with increasing ion strength of solution, while the adsorption capability of Phe increased with the increasing degree of CH3 functionalization on SBA-15. For neutral amino acid Phe, Ala, and Leu, the adsorption capability increased with the increase of the length of their side chains, which was another evidence of hydrophobic effect. Thus, all the adsorption of amino acids on mesoporous silica materials can be decided by the combined influence of two fundamental interactions: electrostatic attraction and hydrophobic effect.     

CZE of Sulfur-Containing Amino Acids and Peptides and Its Application to the Quantitative Study of Heavy Metal-Caused Thiol Oxidations

The redox-active, sulfur-containing amino acids cysteine and methionine, the tripeptide glutathione and their oxidized counterparts cystine, methionine sulfoxide, and glutathione disulfide were separated as anions by capillary zone electrophoresis (CZE) in a 72?cm long fused silica capillary filled with 100?mM phosphate buffer, pH 8.0, at a voltage of +30?kV in 20?min. The optimized CZE method was suited for the implementation of quantitative metal interaction studies of the biomolecules in a biologically relevant concentration range (μM–mM). Decreasing peak areas of the reduced forms of cysteine and glutathione and simultaneously increasing peak areas of the oxidized forms after incubation of the reduced biomolecules with divalent heavy metal cations indicated redox reactions which could be responsible for toxic metal actions in biological systems. CZE measurements revealed that a 50?% oxidation grade of cysteine was achieved at a molar metal:cysteine ratio of 0.85 in case of Zn(II) addition and of 0.11 in case of Cu(II) addition, respectively. Cu(II) oxidized 50?% of the initial glutathione at a molar Cu:peptide ratio of 0.036, whereas the 50?% oxidation grade was not reached after incubation with Co(II) up to a molar ratio of Co:peptide of 0.25.     

Conductivity of Phosphoric Acid, Sodium, Potassium, and Ammonium Phosphates in Dilute Aqueous Solutions from 278.15 K to 308.15 K

Precise conductivity measurements on aqueous solutions of phosphoric acid, sodium dihydrogen phosphate, potassium dihydrogen phosphate, ammonium dihydrogen phosphate, disodium hydrogen phosphate, dipotassium hydrogen phosphate, diammonium hydrogen phosphate, sodium phosphate, and potassium phosphate were performed from 5 to 35°C. Data analysis was executed by the use of the Quint–Viallard equation for unsymmetrical electrolytes. Equations are given for the concentration dependence of electrolyte and single-ion conductivities at all temperatures.     

Photochemical addition of amino acids and peptides to homopolyribonucleotides of the major DNA bases

Abstract— The photochemical quantum yields for addition of glycine and the L-amino acids commonly occurring in proteins (excluding proline) to polyadenylic acid, polycytidylic acid, polyguanylic acid and polyribothymidylic acid have been determined in deoxygenated phosphate buffer at Λ 254 nm and pH 7, using a fluorescamine assay technique. Polyadenylic acid was reactive with eleven of the twenty amino acids tested, with phenylalanine, tyrosine, glutamine, lysine and asparagine having the highest quantum yields. Polyguanylic acid reacted with sixteen amino acids; phenylalanine, arginine, cysteine, tyrosine, and lysine displayed the largest quantum yields. Polycytidylic acid showed reactivity with fifteen amino acids with lysine, phenylalanine, cysteine, tyrosine and arginine having the greatest quantum yields. Polyribothymidylic acid, reactive with fifteen of nineteen amino acids surveyed, showed the highest quantum yields for cysteine, phenylalanine, tyrosine, lysine and asparagine. None of the polynucleotides were reactive with aspartic acid or glutamic acid.
The quantum yields for photoaddition of eighteen dipeptides of the form glycyl X (X being one of the amino acids commonly occurring in proteins, including proline), and of L-alanyl-L-tryptophan, L-seryl-L-seryl-L-serine, L-threonyl-L-threonyl-L-threonine, L-cystine- bis -glycine, and N_α-acetyllysine to polyadenylic acid, polycytidylic acid and polyguanylic acid were measured. All of these were found to add photochemically to each of these polymers. Polyribothymidylic acid, tested with eleven of these peptides and with N_α-acetyllysine, was found to be reactive with all.