Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: C35E7 .10
 63,145 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Residues of two antibacterial agents, cephalexin and colistin, co-administered by intramuscular injection to calves, were quantified in four different tissues (muscle, fat, liver and kidney) by column switching HPLC and by a microbiological method. For cephalexin assay, tissue samples with cephradin as internal standard were homogenized in a 5% trichloroacetic acid solution and filtrates were injected onto a concentration precolumn filled with LiChroprep RP-18 (25-40 microns). A clean-up step was incorporated by flowing a mobile phase (methanol-0.01 M phosphate buffer (pH 3.0); 15:85, v/v) through the enrichment column before elution on a LiChrospher RP-18e (5 microns) column with a methanol-phosphate buffer (30:70, v/v) at a flow rate of 1 ml min-1. Spectrometric detection was at 260 nm. An additional "off-line" washing step of extracts with methylene chloride was operated to achieve higher selectivity in the case of liver and kidney samples. The limit for quantitative assay was 0.045 micrograms g-1 with relative standard deviations in the range 5-8% and recoveries within 70%. For microbiological assay of colistin, samples were homogenized in 0.1 M hydrochloric acid-acetonitrile mixtures (3:1, v/v, for kidney and liver; 3:2, v/v, for fat and muscle). The supernatants were assayed by the cylinder plate method after evaporation to dryness under vacuum. Bordetella bronchiseptica ATCC 4617 was chosen as test organism. After a 3-h diffusion step at room temperature, the medium was incubated at 37 degrees C for 18 h and then the diameter of the growth inhibition zones was measured. Sensitivity reached 0.10-0.15 micrograms g-1. Results from the analysed samples over a 7-28 day period after drug administration show that no cephalexin was found at concentrations higher than the quantitation limit in the four test tissues and that colistin was found in muscle (injection site only) for 15 days and in kidney for 21 days.
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PMID:Residue determination of two co-administered antibacterial agents--cephalexin and colistin--in calf tissues using high-performance liquid chromatography and microbiological methods. 249 May 72

It is shown that methanol significantly decreases the rate of ATP-dependent activation of submitochondrial particle ATPase blocked by low (approximately 1 microM) ADP concentrations, having an insignificant effect on the initial rate of ATP hydrolysis. The dissociation rate constant for the F1.ADP complex (Kd = approximately 2.10(-8) M) decreases thereby from 0.28 to 0.12 min-1. Within a narrow range of ADP concentrations (2-40 microM) used to inhibit ATPase, the activation rate constant measured in the presence of methanol changes from the minimum (0.12 min-1) to the maximum (0.48 min-1) value. The rate of dissociation of the enzyme-inhibitor complexes formed in the presence of low (approximately 1 microM) or high (greater than or equal to 40 microM) ADP concentrations depends on the concentration of ATP in a similar way. In the presence of EDTA, the enzyme-inhibitor complex (ADP.F1.ADP) is activated within 1-3 minutes, whereas the dissociation of the F1.ADP complex proceeds on an hour scale. The results obtained are interpreted as the interaction of at least three nucleotide-binding sites in the membrane-bound F1.
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PMID:[Kinetic evidence of the interaction of three nucleotide-binding centers of mitochondrial ATP-synthetase]. 251 Aug 33

A liquid chromatographic method for the determination of penicillin V potassium in tablets was collaboratively studied by 7 laboratories. The method uses an octadecyl silane reverse-phase column, a mobile phase of acetonitrile-methanol-0.01 M potassium phosphate monobasic (21 + 4 + 75 v/v/v), photometric detection at 225 nm, and sulfadimethoxine as an internal standard. Each collaborator received 6 samples: powdered composites of 2 commercial tablet preparations and 1 synthetic tablet powder mixture, each with blind duplicates. The mean repeatability and reproducibility relative standard deviations for commercial samples were, respectively, 1.10 and 1.46% (250 mg dosage), and 0.84 and 2.82% (500 mg dosage). The average standard recovery from the synthetic formulation was 99.1%, with repeatability and reproducibility relative standard deviations of 1.30 and 3.66%, respectively. The method has been adopted official first action.
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PMID:Liquid chromatographic determination of penicillin V potassium in tablets: collaborative study. 251 78

A procedure for determination of rifampicin and 25-desacetylrifampicin in plasma by HPLC was developed. The plasma proteins are precipitated by acetonitrile and the supernatant layer (50 microliters) is used for the assay under isocratic conditions on an analytical column 250 x 4.6 mm in size containing the reversed phase sorbent (C18). The size of the precolumn is 50 x 4.6 mm. An UV detector (at lambda 335 nm) is used. For preparing the mobile phase 630 ml of methanol and 370 ml of 0.058 M sodium nitrite solution are mixed. The flow rate of the mobile phase is 40.7 ml/min. The assay duration is about 10 min. The retention time is 9.6 min for rifampicin and 6.5 min for 25-desacetylrifampicin. The minimum detectable amount of the antibiotic and its metabolite is 0.10 micrograms/ml. The standard curves of rifampicin and 25-desacetylrifampicin are linear within the concentration ranges of 0.5-100 and 0.5-10 micrograms/ml respectively. The procedure is useful in studies on pharmacokinetics of rifampicin and 25-desacetylrifampicin.
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PMID:[Quantitative analysis of rifampicin and 25-desacetylrifampicin in the plasma using high performance liquid chromatography]. 261 May 36

Dextromoramide and pethidine were separated and identified by thin-layer chromatography on silica gel, using ammonia and methanol (1.5:100) as the mobile phase, after previous extraction with dicthyl ether or with a mixture of n-hexane and isoamyl alcohol (98.5:1.5) from blood alkalized to pH 10.3 Dextromoramide can be revealed on the chromatograms in the amount of 0.5 micrograms and pethidine in the amount of 1 micrograms using the Dragendorff reagent. Reversed-phase TLC proved less sensitive. High-performance liquid chromatography on the column of LiChrosorb RP-18 was applied to the determination of dextromoramide in blood after extraction with diethyl ether, using methanol--phosphate buffer pH 4.5 (95:5) as the mobile phase. The determination range was of 0.5-5.0 micrograms per 2 cm3 of blood plasma (1.26.10(-8)-1.26.10(-7) mole/dm3).
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PMID:[Chromatographic identification and analysis of dextromoramide in the plasma by the method of high performance liquid chromatography]. 263 68

A new method is described for the determination of the herbicide fluazifop-butyl, and its metabolite fluazifop acid, in soybeans and soybean oil as fluazifop acid. Liquid chromatography with amperometric detection (LC/AD) is used to determine fluazifop acid produced from the metabolism or base hydrolysis of fluazifop-butyl in soybeans and soybean oil. These foods were spiked with fluazifopbutyl at 0.05, 0.10, and 0.50 ppm and hydrolyzed with 0.2N NaOH in methanol. The hydrolysate (adjusted to pH less than or equal to 1) is extracted with dichloromethane and the extract is washed with 1.0% NaHCO3. The NaHCO3 is acidified to pH less than or equal to 1 and extracted with dichloromethane; the partitioning is repeated 2 more times. The dichloromethane is removed, mobile phase solvent is added, and aliquots are injected onto a PRP-1 liquid chromatographic column; fluazifop acid is separated from coextracted compounds and detected at an applied potential of + 1.25 V, using an amperometric electrochemical detector in the oxidation mode. Recoveries ranged from 69 +/- 6.5 to 101 +/- 18% and from 72 +/- 7.5 to 88 +/- 11% for soybeans and soybean oil, respectively. Accuracy of these recoveries was confirmed by use of 14C-radiolabeled fluazifop-butyl and by liquid scintillation spectrometry of the 14C-fluazifop acid released.
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PMID:Determination of fluazifop-butyl and fluazifop acid in soybeans and soybean oil using liquid chromatography with oxidative amperometric detection. 270 88

The crystalline formate dehydrogenase from Candida methanolica, which showed the highest specific activity (7.52 U/mg) so far reported, was characterized in detail. The enzyme is a dimer composed of identical subunits, each containing one SH group related to the catalytic activity. The molecular mass of the enzyme is about 82-86 kDa. The Km values were found to be 3.0 mM for formate and 0.11 mM for NAD+. Even if the enzyme was incubated at pH 6.5-9.5 or at 55 degrees C, the activity remained at 100%. Hg2+, Ni2+, NaCN, NaN3 and p-chloromercuribenzoate strongly inhibited the enzyme activity, while the enzyme showed relatively high resistance to various chelating agents. The amino acid composition and some other physicochemical properties of the enzyme were studied. Immunological studies revealed that formate dehydrogenases of methanol-utilizing yeasts immunologically more or less resemble each other, but differ from those of methanol-utilizing bacteria. Furthermore, yeast formate dehydrogenases can be immunologically classified into three types: (a) the Candida type, (b) the Torulopis/Hansenula/Pichia type and (c) the formaldehyde-resistant yeast type. For simple and large-scale preparation of the enzyme for practical use, treatment of cells of C. methanolica with the commercial cationic detergent, 'Benzalkonium' cation, is useful: the total and specific activities of the enzyme are 1.17-fold and 3.10-fold higher than those of the crude cell-free extract, respectively.
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PMID:Characterization of crystalline formate dehydrogenase from Candida methanolica. 273 6

Formaldehyde resistance of methylotrophic and non-methylotrophic Acetobacter strains was investigated. A facultatively methylotrophic Acetobacter methanolicus (MB58) gets rid of free formaldehyde by assimilating it. Heterotrophically growing cells tolerate 12 mM free formaldehyde. Non-methylotrophic but methanol oxidizing Acetobacter pasteurianus strains possess the same level of formaldehyde resistance. Formaldehyde resistance can be drastically lowered down to 4 mM by blocking the formate dehydrogenase by means of hypophosphite. Acetobacter spp. Martin 1 and LMG 76.10 are not able to oxidize methanol or formaldehyde via formate to CO2 and possess a significantly lower formaldehyde resistance (4 mM). Hence high formaldehyde resistance of the Acetobacter spp. investigated is based above all on a properly operating linear dissimilatory sequence. The dissimilatory RuMP cycle can hardly help detoxify formaldehyde.
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PMID:Detoxification of formaldehyde by acetic acid bacteria. 277 25

A new method is described for the determination of submicromolar concentrations of 5-bromodeoxyuridine in human plasma. Sample pretreatment involves cold methanol deproteinization, freezing-thawing and lyophilization. The sample is then analysed by reversed-phase high-performance liquid chromatography. This method is very reproducible and has a detection limit of 0.1 microgram/ml (0.32.10(-6) M). Comparison with other procedures indicates that the method is advantageous as regards sensitivity and specificity and can be readily applied in clinical pharmacological investigations.
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PMID:High-performance liquid chromatographic determination of 5-bromodeoxyuridine in human plasma. 279 67

In the present communication, synthesis and DNA binding activities of three analogs of the antibiotic netropsin are reported. Each analog contains two N-propylpyrrolecarboxamide units linked covalently to either Dns-Gly-Val-Val-Val-Gly-Gly- (I), Val-Val-Val-Gly-Gly (II) or Gly-Gly (III). It is shown that analogs I and II can self-associate in aqueous solution and methanol as revealed from the fact that UV absorbance and circular dichroism spectra obtained for these analogs are concentration-dependent. By contrast, analogs III exists as a monomer, even at concentration levels of the order of 1.10(-3) M. Determination of the apparent sizes of intramolecular aggregates by gel-filtration shows that analog I in aqueous solution at concentration levels of the order of 1.10(-3) M forms a series of aggregates containing from 2 to 12 monomers. Analog II exhibits a lower tendency to form intermolecular aggregates as compared with that of analog I. Dimerization constants are determined for analogs I and II in aqueous solution and methanol. The binding of N-propylpyrrolecarboxamide units and peptide fragments of analog I to DNA can be independently monitored by circular dichroism and fluorescence methods. If self-associated species of analog I (or II) are present in solution, the ligand exhibits a markedly different order of base pair sequence preferencies as compared with that of analog III. The results obtained are consistent with the inference that analogs I and II in a beta-associated form recognizes base pair sequences containing two runs of 3 AT pairs separated by two GC pairs.
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PMID:[Attachment of trivaline changes the specificity of binding of netropsin analogs with DNA]. 283 19


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