铁氰化钾-钙黄绿素体系后化学发光反应测定氨基比林

研究发现,氨基比林在铁氰化钾-钙黄绿素化学发光反应体系中的后化学发光反应。优化了反应条件,建立了一种利用后化学发光反应测定氨基比林的流动注射化学发光方法。方法的检出限为20μg/L;相对标准偏差为2.0%(2.0mg/L氨基比林,n=11);线性范围为1.0×10-4~1.0×10-2g/L。此法已用于复方氨林巴比妥注射液中氨基比林含量的测定,结果与药品标准方法测定值一致。     

流动注射后化学发光法测定Ca~(2+)

实验发现Ca2+在铁氰化钾-钙黄绿素化学发光反应体系中的后化学发光反应.优化了反应条件,建立了一种利用后化学发光反应测定Ca2+的流动注射化学发光分析法.方法的线性范围为1.0×10-6～1.0×10-4 g/mL,检出限为3.0×10-7 g/mL, 相对标准偏差为1.8%(2.0×10-5 g/mL Ca2+,n=11).此法已用于自来水中Ca2+含量的测定,结果与标准方法测定值一致.     

铁氰化钾-钙黄绿素体系流动注射化学发光法测定孔雀石绿

基于在碱性条件下,孔雀石绿可以增强铁氰化钾-钙黄绿素的化学发光,且其浓度在一定范围内与化学发光强度呈线性关系,结合流动注射技术,建立了化学发光法测定孔雀石绿的新方法。在优化的实验条件下,方法的线性范围为3.0×10-8～1.0×10-6 g/mL,检出限为2.5×10-9 g/mL,对浓度为1.0×10-7g/mL的孔雀石绿溶液进行11次平行测定,相对标准偏差为2.3%。方法可应用于环境水样的测定。     

溴酸钾-酸性铬蓝K化学发光法检测水中微量NO2-

利用NO2-对溴酸钾-酸性铬蓝K体系的化学发光有显著的增强作用,建立了检测亚硝酸盐的新方法。着重对化学发光条件,包括溴酸钾浓度、酸性铬蓝K浓度、管长、流速及酸度条件进行了实验研究,并利用该方法对地下水及当地雨水进行了检测。实验结果表明,当溴酸钾浓度为0.1 mol/L、酸性铬蓝K浓度为1.0×10-4mol/L、管长为40 cm、流速为2.5 mL/min及硫酸为0.5 mol/L时,本方法检测NO2-的线性范围为1.0×10-8~8.0×10-5mol/L,检出限为1.1×10-10mol/L;对1.0×10-7mol/L和1.0×10-5mol/L的NO2-进行11次平行测定,相对标准偏差分别为1.6%和2.1%;对天然水中NO2-检测,结果满意。对化学发光机理进行了初步探讨。     

钙黄绿素-H2O2抑制化学发光法测定土壤中的Cd(Ⅱ)

在碱性条件下,根据Cd(Ⅱ)离子对H2O2-钙黄绿素化学发光体系有较强的抑制作用的现象,结合流动注射分析技术,建立了一种化学发光定量测定Cd(Ⅱ)的新方法.实验结果表明,该方法对Cd(Ⅱ)的检出限为5.7×10-5 g/L,工作曲线线性范围为1.0×10-4～5.0×10-3 g/L,测定浓度为5.0×10-4 g/LCd(Ⅱ)的相对标准偏差为2.1%(m=11),该法应用于两种土壤样品的测定,加标回收率分别为97.2%、101.8%.     

蔬菜中有机磷农药辛硫磷的化学发光分析研究

研究发现,在碱性介质中,无机盐氯化钠显著增强有机磷农药辛硫磷在鲁米诺-H2O2体系中的化学发光信号,据此建立了测定辛硫磷的化学发光新方法并探讨了该化学发光反应的可能机理.在鲁米诺分析液浓度为5×10-4 mol/L,H2O2溶液浓度为0.3 mol/L,NaCl浓度为4 mol/L,pH值为13的条件下,辛硫磷的浓度在1.0×10-5～1.0×10-3 g/L范围内与化学发光强度呈良好的线性关系;检出限为5.4×10-6 g/L;对浓度为5.0×10-4 g/L的辛硫磷进行11次平行测定,相对标准偏差为4.6%;添加3水平(0.01～1.0 mg/kg)的回收率为86%～106%.本方法用于蔬菜中辛硫磷残留量的测定,结果与气相色谱法基本一致.     

Ru(bipy)2+3-CO2-3-SO2-3-KClO3体系化学发光法测定空气中的二氧化硫

提出了Ru(bipy) 2+ 3-CO 2- 3-SO 2- 3-KClO 3体系化学发光法测定溶液中亚硫酸盐的方法.SO 2- 3浓度与化学发光强度在1.0×10-7～1.0×10-4 mol/L 范围内成正比,检出限为8.76×10-8 mol/L,对1.0×10-4 mol/L SO2-3溶液6次测定的相对标准偏差为2.9%.该法用三乙醇胺作为吸收液,成功地用于测定空气中二氧化硫的含量,结果满意.     

流动注射化学发光法测定中药材中没食子酸

建立快速简便的流动注射化学发光分析法,用于中药材中没食子酸含量的测定.利用酸性介质中Fe3+-H2O2体系生成羟基自由基氧化没食子酸产生微弱的化学发光,用罗丹明6G来增敏化学发光.研究了影响化学发光的各种因素,探讨了可能的机理.结果表明,0.18 mol/L HCl,0.04 mol/L FeCl3,1.0 mol/L H2O2与1.0×10-4 mol/L罗丹明6G溶液组成最优的化学发光体系,没食子酸浓度在1.0×10-5～1.0×10-2 g/L和0.01～1.0 g/L范围内与化学发光强度呈很好的线性关系,r分别为0.9984和0.9947,检出限为3.0×10-6 g/L.对1.0×10-4 g/L没食子酸平行测定11次的相对标准偏差为3.8%.利用本方法成功地测定了中药材诃子和没食子中的没食子酸含量.     

铁氰化钾-钙黄绿素体系后化学发光反应测定盐酸硫利达嗪

报道了盐酸硫利达嗪在铁氰化钾-钙黄绿素化学发光反应体系中的后化学发光反应。优化了反应条件,并建立了一种利用后化学发光反应测定盐酸硫利达嗪的流动注射化学发光分析法。方法的检出限为2.0×10-7g/mL,对2.0×10-6g/mL盐酸硫利达嗪测定的相对标准偏差为2.0%(n=11),线性范围为5.0×10-7～5.0×10-5g/mL。该法已用于盐酸硫利达嗪片剂中盐酸硫利达嗪含量的测定,结果与药典方法测定值一致。     

鲁米诺-[铁氰化钾-亚铁氰化钾]-酚磺乙胺化学发光体系

实验发现 ,酚磺乙胺与鲁米诺在碱性溶液中可产生弱的化学发光 ,铁氰化钾和亚铁氰化钾的存在对该化学发光反应具有很强的催化作用。基于此 ,建立了基于鲁米诺 铁氰化钾 /亚铁氰化钾 酚磺乙胺体系测定酚磺乙胺的流动注射化学发光新方法。酚磺乙胺浓度在 4 .0× 10 -6～ 1.0× 10 -4g/L范围内与化学发光强度具有线性关系。该方法的检出限为 1× 10 -6g/L ,相对标准偏差为 1.4 % (2 .0× 10 -5g/L酚磺乙胺溶液 ,n =11)。该方法用于止血敏注射液中酚磺乙胺的含量测定 ,结果令人满意。同时 ,还对可能的化学发光反应机理进行了初步探讨     

Enantiomer separation by CEC——Enantiomer separation by packed-capillary electrochromatography

Three chiral compounds were successfully separated in a short time with two enantiomer separation models on packed-capillary electrochromatography (CEC). (i) 75 μm I.D. capillaries were packed with 5 μm β-cyclodextrin (β-CD) chiral stationary phase (CSP). Effects of voltage, pH and concentration of organic modifier on electroosmotic flow (EOF) and chiral separations were investigated systematically. Enantiomers of a neutral compound (benzoin) and a neutral drug (mephenytoin) were separated within a short time with high efficiency. Efficiency of 32 000 theoretical plates per meter and resolution (R_s) of 1.42 were achieved for enantiomers of benzoin using a βCD packed column with 6.2 cm packed length. Efficiency of 45 000 theoretical plates per meter and R_s of 3.40 were obtained for enantiomers of mephenytoin. Especially, the enantiomer separation of mephenytion was performed in just 3.4 min with R_s of 2.60. (ⅱ) 75 μm I.D. capillary was packed with octadecylsilica particles (ODS). Chiral separat     

Regioselectivity of olefin oxidation by iodosobenzene catalyzed by metalloporphyrins : control by the catalyst

The regioselectivity of the oxidation of three monosubstituted olefins, 6-phenoxyhex-1-ene, hex-1-ene and styrene, by iodosobenzene in the presence of various Fe-, Mn- or Cr-tetraaryl-porphyrins, was studied. It was found that, besides epoxides, known products from such systems, allylic alcohols and aldehydes were formed, the latter not being derived from the corresponding epoxides. The relative importance of these reactions greatly depends upon both the metal and porphyrin constituents of the catalyst. More particularly, the competition between epoxidation and allylic hydroxylation can be efficiently controlled by non-bonded interactions between the olefin and porphyrin substituents. No hydroxylation of the aromatic rings and no oxidative dealkylation of the ether function was detected.     

Glycosidase inhibition by macrolide antibiotics elucidated by STD-NMR spectroscopy

A glycosynthase approach was attempted to glycodiversify macrolide antibiotics, using DesR, a family-3 retaining beta-glucosidase involved in the self-resistance mechanism of methymycin production. STD-NMR was used to probe enzyme-substrate interactions. Analysis of competitive STD-NMR experiments between erythromycin A and a chromogenic substrate (pNP-beta-d-glucose) with the hydrolytically inactive nucleophile mutants led us to discover a family of unprecedented glycosidase inhibitors. Analysis of kinetic data with wild-type DesR determined that erythromycin is a competitive inhibitor of the glucosidase (IC50 = 2.8 +/- 0.3 microM and Ki = 2 +/- 0.2 microM) with respect to the hydrolysis of pNP-beta-d-glucose. Comparable inhibitory data was obtained for clarithromycin; however, the inhibitory effect of azithromycin was weak and no significant inhibition was observed with methymycin or d-desosamine. This report documents significant inhibition of glycosidases by macrolide antibiotics and provides insight into the design of novel glycosidase inhibitors based on the macrolactone ring of macrolide antibiotics.     

Membrane solubilization by detergent: resistance conferred by thickness

The commonly held model for membrane dissolution by detergents/surfactants requires lipid transport from the inner to the outer bilayer leaflet ('flip-flop'). Although applicable to many systems, it fails in cases where cross-bilayer transport of membrane components is suppressed. In this paper we investigate the mechanism for surfactant-induced solubilization of polymeric bilayers. To that end, we examine the dissolution of a series of increasingly thick, polymer-based vesicles (polymersomes) by a nonionic surfactant, Triton X-100, using dynamic light scattering. We find that increasing the bilayer thickness imparts better resistance to dissolution, so that the concentration required for solubilization, after a fixed amount of time, increases nearly linearly with membrane thickness. Combining our experimental data with a theoretical model, we show that the dominant mechanism for the surfactant-induced dissolution of polymeric vesicles, where polymer flip-flop across the membrane is suppressed, is the surfactant transport through the bilayer. This mechanism is different both qualitatively and quantitatively from the mechanisms by which surfactants dissolve pure lipid vesicles.     

Antibiotic recognition by binuclear metallo-beta-lactamases revealed by X-ray crystallography

Metallo-beta-lactamases are zinc-dependent enzymes responsible for resistance to beta-lactam antibiotics in a variety of host bacteria, usually Gram-negative species that act as opportunist pathogens. They hydrolyze all classes of beta-lactam antibiotics, including carbapenems, and escape the action of available beta-lactamase inhibitors. Efforts to develop effective inhibitors have been hampered by the lack of structural information regarding how these enzymes recognize and turn over beta-lactam substrates. We report here the crystal structure of the Stenotrophomonas maltophilia L1 enzyme in complex with the hydrolysis product of the 7alpha-methoxyoxacephem, moxalactam. The on-enzyme complex is a 3'-exo-methylene species generated by elimination of the 1-methyltetrazolyl-5-thiolate anion from the 3'-methyl group. Moxalactam binding to L1 involves direct interaction of the two active site zinc ions with the beta-lactam amide and C4 carboxylate, groups that are common to all beta-lactam substrates. The 7beta-[(4-hydroxyphenyl)malonyl]-amino substituent makes limited hydrophobic and hydrogen bonding contacts with the active site groove. The mode of binding provides strong evidence that a water molecule situated between the two metal ions is the most likely nucleophile in the hydrolytic reaction. These data suggest a reaction mechanism for metallo-beta-lactamases in which both metal ions contribute to catalysis by activating the bridging water/hydroxide nucleophile, polarizing the substrate amide bond for attack and stabilizing anionic nitrogen intermediates. The structure illustrates how a binuclear zinc site confers upon metallo-beta-lactamases the ability both to recognize and efficiently hydrolyze a wide variety of beta-lactam substrates.