1,720,955 research outputs found
ENHANCED FLUORIMETRIC DETERMINATION OF EUROPIUM(III) WITH THENOYLTRIFLUOROACETONE AND 4,7-DIPHENYL-1,10-PHENANTHROLINE BY GADOLINIUM(III)
No full textChemistry, AnalyticalSCI(E)37ARTICLE81499-15132
SPECTROFLUORIMETRIC DETERMINATION OF HYDROGEN-PEROXIDE BASED ON THE CATALYTIC EFFECT OF PEROXIDASE-LIKE MANGANESE TETRAKIS(SULPHOPHENYL) PORPHYRIN ON THE OXIDATION OF HOMOVANILLIC-ACID
No full textChemistry, AnalyticalSCI(E)38NOTE2299-30223
Electrochemical method for analyzing intracellular redox activity changes of the etoposide-induced apoptosis in HL-60 cells
No full textAn electrochemical method for analyzing HL-60 cell apoptosis (programmed cell death) induced by etoposide was examined. The cyclic voltammetric response of HL-60 cells was observed over the life-cycle of apoptotic cells. It showed that the oxidation peak current of cells decreased with etoposide treatment. The decrease of peak current of HL-60 cells appeared at 2 mu g ml(-1) etoposide treatment after 24 h and became significant at 20 mu g ml(-1), which occurred before the typical changes of cell morphology and DNA contents caused by apoptosis. Flow cytometric-DNA (FCM-DNA) analysis revealed that 10.5-20% of the cells were apoptotic while the peak current decreased from 1.8 to 0.4 mu A after 2-4 h of treatment with 200 mu g ml(-1) etoposide. Changes of cyclic voltammetric response during the early stages of apoptosis are attributed to changes in the intracellular redox reactivity of HL-60 cells. The electrochemical responses of living cells can be used for probing intracellular redox activity-of initiation of apoptosis and analyzing the whole process of apoptosis. (C) 2000 Elsevier Science B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000087961900013&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, AnalyticalSCI(E)16ARTICLE2221-22641
FLUORESCENCE REACTION OF TERBIUM(III) WITH NUCLEIC-ACIDS IN THE PRESENCE OF PHENANTHROLINE
No full textThe fluorescence enhancement reaction of terbium(III) with DNA or RNA in the presence and absence of phenanthroline (Phen) was studied. Studies involving natural and denatured calf thymus DNA, fish sperm DNA and yeast RNA revealed that the presence of phen enhanced the net fluorescence 3-12 fold. The results suggest a 1:2 molar ratio of terbium(III) and phen for the ternary complex. Maximum fluorescence was produced in the pH range 6.8-7.2. The calibration graphs were linear between 0.4 and 15.0 or 20.0-mu-g ml-1 for thermally denatured nucleic acids and the detection limits were 0.1-0.2-mu-g ml-1. The relative standard deviation (six replicates) was within 3.0% in the linear range. Yeast RNA could be determined in the presence of up to 40% calf thymus DNA and the latter was determined when the content of yeast RNA in synthetic samples was below 10%.Chemistry, AnalyticalSCI(E)135ARTICLE2589-59424
FLUORESCENCE LABELING WITH EUROPIUM CHELATE OF BETA-DIKETONES AND APPLICATION IN TIME-RESOLVED FLUOROIMMUNOASSAYS (TR-FIA)
No full textFive beta-diketone derivatives were studied for multiple labelling of proteins. The labelled proteins were characterized by absorption and fluorescence measurements. It was found that proteins labelled with chlorosulfonylthenoyltrifluoroacetone (CTTA) were able to form highly fluorescent complexes with Eu3+ which exhibited prolonged fluorescence whereas the Eu3+ complex of hydrolyzed CTTA exhibited almost no fluorescence, and so unreacted ligand gave no background signal in immunoassays even if it was not removed from the labelled reagent. The effect of labelling on the biological activity of albumin and polyclonal antibody was studied and it was also shown that the new probe could be used in time-resolved fluorescence immunoassays.Biochemical Research MethodsImmunologySCI(E)PubMed25ARTICLE2233-24117
Human Breast Carcinomal Tissues Display Distinctive FTIR Spectra: Implication for the Histological Characterization of Carcinomas
No full textFourier transform infrared spectroscopic study of human breast normal and carcinomal tissues has been carried out. Some distinctive spectral differences which are mainly due to nucleic acids and proteins are observed between normal and carcinomal tissues. This method of analysis results in nearly 100% diagnostic accuracy of carcinomal tissues from normal tissues. The spectral patterns of well‐differentiated carcinomal tissues exhibit marked heterogeneity, however that of poorly differentiated carcinomas demonstrate significant similarity. Apocrine, tubular, intraductal and mucinous carcinomas and invasive infiltrating ductal carcinomal tissues can be discriminated based on their characteristic spectra. The spectral differences confirm the possibility of using FTIR as an accurate and rapid technique to distinguish between normal and malignant breast tissues and classify breast carcinomas in different subtypes
FLOW-INJECTION AND LIQUID-CHROMATOGRAPHIC POSTCOLUMN DETECTION OF AMINO-ACIDS BY MIMETIC PEROXIDASE-CATALYZED CHEMILUMINESCENCE REACTION
No full textFour amino acids were determined on the basis of the finding that the catalytic activity of mimetic peroxidase (metalloporphyrin) in the chemiluminescence reaction between luminol and hydrogen peroxide is inhibited in the presence of an amino acid. The degree of chemiluminescence inhibition is a measure of the amino acid concentration. The electrostatic interaction between amino acid and metalloporphyrin was confirmed by comparing the degree of inhibition of cationic and anionic metalloporphyrin-catalysed chemiluminescence reactions. More than 20 amino acids were tested, and only L-cysteine, L-tyrosine, L-tryptophan and L-cystine significantly quenched the chemiluminescence intensity. Detection limits were 6.8 X 10(-8), 1.3 X 10(-7), 8.5 X 10(-6) and 2.2 X 10(-5) M, respectively. The detection approach is demonstrated with a silica-based liquid chromatographic separation of amino acids using phosphate buffer (pH 7.3) as mobile phase. Compared with other chemiluminescence analyses, this method is faster, can be run at room temperature and, in favourable cases, has a lower detection limit.Chemistry, AnalyticalSCI(E)20ARTICLE1109-11426
CHEMILUMINESCENCE INVESTIGATION OF THE INTERACTION OF METALLOPORPHYRINS WITH NUCLEIC-ACIDS
No full textThe interaction of water-soluble cationic porphyrin meso-tetrakis(4-N-methylpyridinyl)porphyrin (TMPyP) manganese derivatives with DNA was demonstrated by their catalytic activity on the luminol-H2O2 chemiluminescence (CL) system. The catalytic activity of Mn-TMPyP on the CL reaction was markedly enhanced when the complex was bound to DNA. The native form of DNA and thermally denatured DNA show the same degrees of enhancement. Different degrees of enhancement were obtained when Mn-TMPyP interacted with RNA and polynucleotides, whereas the interaction of nucleotides and bases with Mn-TMPyP had no effect on its catalytic activity. To examine the effect of the peripheral group of the porphyrin on its bonding properties, the interaction of manganese tetrakis(4-aminophenyl)porphyrin (Mn-TPPA(4)), manganese tetrakis(carboxylphenyl)porphyrin (Mn-TPPC4), manganese tetrakis(sulphophenyl)porphyrin (Mn-TPPS4) and manganese tetrakis(4-trimethylaminophenyl)porphyrin (Mn-TAPP) with DNA was tested. Only the Mn-TPPA(4)-catalysed CL reaction was significantly enhanced. The effects of the native form of DNA and thermally denatured DNA on the Mn-TPPA(4)-catalysed CL reaction were very different to that on the Mn-TMPyP-catalysed CL reaction. With a fixed concentration of Mn-TMPyP there was a saturated concentration of DNA with respect to the metalloporphyrin (M-P). The binding number of M-P to DNA was estimated. Optimum conditions of the M-P-DNA complex-catalysed luminol CL reaction were evaluated by using a low-injection system. The use of the analytical parameters of the phenomenon as a means of determining DNA was examined. The detection limit (signal-to noise ratio > 3) of DNA was 0.20 ng ml(-1). The relative standard deviation (n = 11) of the determination of 10 ng ml(-1) DNA was 2.6%.Chemistry, AnalyticalSCI(E)38ARTICLE3695-70128
FTIR investigation of the interaction of tumor cells treated with caffeic acid and chlorogenic acid
No full textFourier transform infrared spectra of U937 cells treated with chlorogenic acid (CGA) and caffeic acid (CA) for 1, 6, 12 and 24h were recorded and analyzed. Some considerable changes in the ratio of the absorbance of the bands at 2960 and 1855 cm(-1) (D-2960/D-2855) and the ratio of the integrated areas of the absorption at 1540 and 1086 cm(-1) (A(1510)/A(1086)) of the spectra of the tumor cells were observed for different times of incubation and drug concentrations. The cells treated for 6h have the highest D-2960/D-2855 and lowest A(1540)/A(1086) ratios. CGA has stronger interaction with U937 than that with CA. These two phenolic acids could interact with both proteins and nucleic acids of tumor cells. And these changes in the spectra of cells could be explained as the degeneration of the protein and nucleic acids in cells. (C) 2000 Elsevier Science B.V. All rights reserved.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000165524100007&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Chemistry, AnalyticalChemistry, PhysicalSpectroscopySCI(E)EI33ARTICLE2225-2312
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