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PubMed2006

Flow-injection enhanced chemiluminescence method for determination of ciprofloxacin in pharmaceutical preparations and biological fluids.

A novel rapid and sensitive analytical method, enhanced chemiluminescence with flow-injection sampling, is described for determination of ciprofloxacin. The method is based on the chemiluminescence reaction of the potassium permanganate-sodium thiosulfate-ciprofloxacin system. An enhanced chemiluminescence reaction was developed, and optimum conditions for CL emission were investigated. The chemiluminescence intensity was linearly dependent on ciprofloxacin concentration in the range 1.0 x 10(-8)-1.0 x 10(-5) g mL(-1). The detection limit was 4 x 10(-9) g mL(-1). The relative standard deviation was 1.8% for eleven measurements of 2.0 x 10(-7) g mL(-1) ciprofloxacin standard solution. The new method enables simple, sensitive, and rapid determination of ciprofloxacin and has been successfully used for determination of ciprofloxacin in biological fluids and in ciprofloxacin hydrochloride tablet and injection.

Antioxidants↗

PubMed2003

Enrichment and properties of an anaerobic mixed culture that reductively deiodinates 5-amino-2,4,6-triiodoisophthalic acid, an X-ray contrast agent precursor.

5-Amino-2,4,6-triiodoisophthalic acid (ATIA), both a precursor and a degradative intermediate of triiodinated contrast media, was anaerobically converted by sludge from a wastewater treatment plant. ATIA conversion took place only when an electron donor such as ethanol was added. A stable mixed culture was established by transfer to a defined synthetic mineral medium with ATIA and ethanol. It could be maintained for 1 year when the sulfate concentration was kept below 30 microM. Transient appearance of 5-amino-2,4-diiodoisophthalic acid, iodide release (2.7 mol iodide/mol ATIA) and accumulation of 5-aminoisophthalic acid indicated that ATIA was reductively dehalogenated. The enriched mixed culture also dehalogenated ATIA derivatives but deiodination remained incomplete. ATIA was the sole terminal electron acceptor used by the mixed culture during deiodination. The ratio of electrons transferred to ATIA, 0.83, was consistent with a respiratory metabolism. Formate, acetate, lactate, butyrate and hydrogen were also used as electron donors. Deiodination was inhibited by a headspace of air or by addition of nitrate, sulfite or thiosulfate. The reaction was 2.6 times slower with sulfate than without.

Acetates↗

PubMed2003

Expression of foreign proteins in Escherichia coli by fusing with an archaeal FK506 binding protein.

Improper protein-folding often results in inclusion-body formation in a protein expression system using Escherichia coli. To express such proteins in the soluble fraction of E. coli cytoplasm, we developed an expression system by fusing the target protein with an archaeal FK506 binding protein (FKBP). It has been reported that an archaeal FKBP from a hyperthermophilic archaeon, Thermococcus sp. KS-1 (TcFKBP18), possesses not only peptidyl-prolyl cis-trans isomerase activity, but also chaperone-like activity to enhance the refolding yield of an unfolded protein by suppressing irreversible protein aggregation. To study the effect of this fusion strategy with FKBP on the expression of foreign protein in E. coli, a putative rhodanese (thiosulfate sulfurtransferase) from a hyperthermophilic archaeon and two mouse antibody fragments were used as model target proteins. When they were expressed alone in E. coli, they formed insoluble aggregates. Their genes were designed to be expressed as a fusion protein by connecting them to the C-terminal end of TcFKBP18 with an oligopeptide containing a thrombin cleavage site. By fusing TcFKBP18, the expression of the target protein in the soluble fraction was significantly increased. The percentage of the soluble form in the expressed protein reached 10-28% of the host soluble proteins. After purification and protease digestion of the expressed antibody fragment-TcFKBP18 fusion protein, the cleaved antibody fragment (single-chain Fv) showed specific binding to the antigen in ELISA. This indicated that the expressed antibody fragment properly folded to the active form.

Archaeal Proteins↗

PubMed1997

Nutritional aspects of dissimilatory sulfate reduction in the human large intestine.

In contrast to other anaerobic ecosystems, such as marine and estuarine sediments, there is a lack of information on the nutritional requirements of human gut sulfate-reducing bacteria (SRB). Various substrates stimulated sulfate reduction in mixed culture, including short-chain fatty acids and other organic acids, alcohols, and amino acids (but not sugars or aromatic compounds). However, the use of sodium molybdate as a specific inhibitor of sulfate reduction caused an accumulation of ethanol and malonate only, and reduced the rate of utilization of lactate. This indicates the importance of these electron donors for sulfate reduction. Since ethanol and lactate are primarily utilized by members of the Desulfovibrio genus, the results suggest a physiologically important role for this group. Experiments with two strains of Desulfovibrio desulfuricans isolated from human feces demonstrated that both were able to reduce sulfite, thiosulfate or nitrate in the absence of sulfate. In addition, one strain (DsvUC1) was able to grow by fermentative metabolism, although the second strain (DsvFD1) showed more restricted fermentative growth. The data indicate that desulfovibrios are ecologically the most significant group of SRB in the human colon, and that colonic isolates belonging to this genus are versatile, in terms of both the electron acceptors and donors that they are able to utilize.

Acetates↗

PubMed2002

Efficient soybean transformation using hygromycin B selection in the cotyledonary-node method.

The efficiency of soybean [Glycine max (L.) Merrill] transformation was significantly increased from an average of 0.7% to 16.4% by combining strategies to enhance Agrobacterium tumefaciens-mediated T-DNA delivery into cotyledonary-node cells with the development of a rapid, efficient selection protocol based on hygromycin B. Wounded cotyledonary-node explants were inoculated with A. tumefaciens carrying either a standard-binary or super-binary plasmid and co-cultivated in the presence of mixtures of the thiol compounds, L-cysteine, dithiothreitol, and sodium thiosulfate. Transformed shoots began elongating only 8 weeks after co-cultivation. Southern analysis confirmed integration of the T-DNA into genomic DNA and revealed no correlation between the complexity of the integration pattern and thiol treatment applied at co-cultivation. All T(0) plants were fertile and the majority of the lines transmitted the beta-glucuronidase (GUS) phenotype in 3:1 or 15:1 ratios to their progenies.

Agrobacterium tumefaciens↗

PubMed1988

Silver staining for carboxymethylated metallothioneins in polyacrylamide gels.

A sensitive method for detecting metallothioneins (MTs) by use of silver staining after sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) of carboxymethylated MTs was developed. Carboxymethylation of metallothioneins is indispensable because it prevents their aggregation, thereby allowing each of them to be detected as a single band by SDS-PAGE. However, when the gel was subjected to the silver-staining method of C. R. Merril, D. Goldman, S. A. Sedman, and M. H. Ebert [(1981) Science 211, 1437-1438], the image of carboxymethylated purified MTs was totally negative. Pretreatment of the gel with 1% sodium thiosulfate just prior to the silver-staining procedure successfully reversed the negative image of carboxymethylated MTs. Further, they could be detected with a limit of nanogram levels per lane. This method can be applied to MTs in cell extracts from cultured cell lines treated with cadmium or to those from liver of cadmium-intoxicated mice.

Animals↗

PubMed1975

Effect of enzymic assay conditions on sulfite reduction catalysed by desulfoviridin from Desulfovibrio gigas.

The type and the amount of end products resulting from sulfite reduction catalysed by a single partially purified desulfoviridin preparation from Desulfovibrio gigas were shown to depend upon the enzymic assay conditions employed. Both manometric and spectrophotometric assays were used, with reduced methyl viologen serving as the electron donor in each system. Trithionate, thiosulfate, tetrathionate and sulfide were identified as possible end products. In the manometric assays, sulfide production was favoured by high reduced methyl viologen concentrations, low sulfite concentrations and a pH value of 7.0 as opposed to 6.0. In the spectrophotometric assays, results approaching the stoichiometric conversion of sulfite to sulfide were obtained only at high initial reduced methyl viologen concentrations.

Desulfovibrio↗

PubMed1976

Denaturation-induced disulfide formation in the enzyme rhodanese.

The effect of denaturants on the quantitation of free sulfhydryl groups in the enzyme rhodanese (thiosulfate sulfurtransferase, EC 2.8.1.1) has been reinvestigated in some detail. The sulfhydryl assay with the colorimetric reagent 5, 5'-dithio-bis (2-nitrobenzoic acid) Nbs2 shows four sulfhydryl groups per enzyme molecule (mol. wt. 32 300) when the colorimetric reagent is added to the assay mixture before the denaturant, sodium dodecyl sulfate. On the other hand, only two sulfhydryl groups per molecule are observed when Nbs2 is added after denaturation has been initiated. The time dependence observed in this latter procedure indicates that the loss of the two groups is rapid and permanent. The results depend on the denaturant used: urea acts like sodium dodecyl sulfate while guanidine reveals four sulfhydryl groups independent of reagent order. The assay also gives four sulfhydryl groups independent of reagent order. The assay also gives four sulfhydryl groups independent of reagent order with urea or sodium dodecyl sulfate under conditions which are expected to limit metal ion-catalyzed oxidation of sulfhydryl groups (e.g. oxygen exclusion or metal ion chelation). Recent studies have shown that rhodanese has a molecular weight of 32 600, no disulfides and four sulfhydryl groups per molecule. These results together with the observations reported here are taken to indicate that a disulfide can be formed during denaturation of rhodanese and that the pathway of denaturation determines the result obtained.

Binding Sites↗

PubMed1976

A reexamination of the postulated charge transfer interactions at the active site of the enzyme rhodanese.

Spectral and kinetic studies of the interaction of N-methylnicotinamide chloride and nicotinamide with the enzyme thiosulphate sulphurtransferase (thiosulphate: cyanide sulfurtransferase, EC 2.8.1.1) (also known as rhodanese) have been performed and compared with previous inhibition data obtained with N-1-(4-pyridyl)pyridinium chloride (NPP). Like NPP both N-methylnicotinamide chloride and nicotinamide are competitive inhibitors of rhodanese with respect to the substrate thiosulfate. Rhodanese binding of N-methylnicotinamide chloride gives rise to no charge transfer absorbtion band. In addition, the free energy of interaction (deltaG0) of NPP with rhodanese is approximately equal to the sum of the individual deltaG0 values of MNA and NA. These compounds are analogous to the two halves of the NPP structure. We conclude that NPP and N-methylnicotinamide chloride are not bound via a charge transfer mechanism. The major stabilizing influence appears to be an ionic interaction with an anionic enzyme site with accessory apolar stabilization. It is postulated that the ionized active site sulfhydryl group in rhodanese could provide the ionic site.

Animals↗

PubMed1976

Spectral studies of the tryptophan exposure in the enzyme rhodanese.

Tryptophan exposure in the enzyme rhodanese (thiosulfate:cyanide sulfur-transferase, EC 2.8.1.1.) has been studied by the methods of solvent perturbation difference spectroscopy, fluorescence spectroscopy and fluorescence quenching. The data from all these techniques are consistent with two classes of tryptophan:surface and buried. The surface residues appear to be relatively shielded and in an anionic environment. The buried residues have spectral characteristics suggesting they are in a very apolar environment and have less than the expected contact with the peptide backbone. The solvent perturbation difference spectra indicate further that additional tyrosine as well as tryptophan residues are buried as rhodanese is converted from the free enzyme to the sulfur-substituted enzyme: forms which are obligatory intermediates in the catalytic cycle.

Animals↗

PubMed1980

Cyanylation of rhodanese by 2-nitro-5-thiocyanobenzoic acid.

Cyanylation of rhodanese (thiosulfate:cyanide sulfurtransferase, EC 2.8.1.1) with a nearly stoichiometric amount of 2-nitro-5-thiocyanobenzoic acid produces a modification of the essential sulfhydryl group. Different S-cyano derivatives are obtained with the enzyme intermediate bearing transferable sulfur bound as a persulfide group (sulfur-rhodanese: E-S-SH) and with the sulfur-free rhodanese (E-SH). The interaction of a neighboring sulfhydryl group splits thiocyanate from the sulfur-rhodanese derivative and cyanide from the sulfur-free rhodanese derivative. In both cases an intramolecular disulfide bond is formed. Iodoacetate is effective on the modified enzyme only after cyanide addition which splits the disulfide so that the essential sulfhydryl group can be alkylated.

Animals↗

PubMed1990

Nucleophilic selectivity and reaction kinetics of chloroethylene oxide assessed by the 4-(p-nitrobenzyl)pyridine assay and proton nuclear magnetic resonance spectroscopy.

The nucleophilic selectivity (Swain-Scott's constant s) of chloroethylene oxide (CEO), an ultimate carcinogenic metabolite of vinyl chloride, was determined to be 0.71 using the 4-(p-nitrobenzyl)pyridine (NBP) assay (Spears method). The molar extinction coefficient of the adduct formed between NBP and CEO was measured; and the second-order rate constants for the reactions of CEO with NBP and with thiosulfate were estimated at three temperatures. The disappearance of CEO and the formation of chloroacetaldehyde (CAA) and glycolaldehyde (GCA) were followed in D2O or a mixture of D2O/hexadeuterated acetone (acetone-d6), using Fourier transform proton nuclear magnetic resonance spectroscopy (1H-FTNMR). Evidence was obtained that CEO reacts with chloride ions to yield CAA at a rate constant of about 17 M-1 h-1 in D2O/acetone-d6 (1 : 1, v/v) at 280 K. Under the same conditions, the first-order rate constant kr for the thermal rearrangement of CEO into CAA was estimated to be approximately 0.41 h-1. These data suggest that the isomerization of CEO may be a minor reaction in physiological saline. These chemical properties of CEO are discussed in relation to the mechanism of vinyl chloride-induced carcinogenesis.

Acetaldehyde↗

PubMed1987

Application of a hepatocyte-erythrocyte coincubation system to studies of cyanide antidotal mechanisms.

A coincubation system composed of hepatocytes in primary monolayer culture and erythrocytes suspended in the culture medium was developed and used as a model for investigations of mechanisms of cyanide antidote action at the cellular level. Hepatocyte ATP was used as the cytotoxicity indicator. Treatment of rat hepatocytes in the coincubation system with KCN (1.0 mM) for 10 min at 37 degrees C selectively reduced hepatocyte ATP levels to 33 +/- 15% of control (no KCN added) levels. 4-dimethylaminophenol (DMAP), cobalt(II) chloride, sodium nitrite, sodium thiosulfate, or a combination of the last two antidotes added to the KCN-containing medium significantly reversed ATP depression and the response was concentration dependent. The relative effectiveness, on a molar basis, was estimated to be DMAP greater than CoCl2 much greater than NaNO2 congruent to Na2S2O3. NaNO2 and DMAP induced methemoglobin formation in the absence of cyanide and cyanmethemoglobin formation in its presence; erythrocytes were required in the medium for effectiveness. CoCl2 produced neither cyanmethemoglobin nor thiocyanate in appreciable quantities nor required erythrocytes for antagonism. Na2S2O3 converted cyanide to thiocyanate and reversed ATP depression without erythrocytes in the medium. The addition of erythrocytes increased these rates significantly and to a greater extent than albumin. The overall results are consistent with previously proposed modes of action for these antidotes. However, the enhancement in cyanide metabolism and ATP recovery with Na2S2O3 and erythrocytes in the system was unexpected and raises the possibility that erythrocytes may contribute to cyanide disposition and antagonism in vivo when this antidote is administered.

Adenosine Triphosphate↗

PubMed1989

Cyanide metabolism in the isolated, perfused, bloodless hindlimbs or liver of the rat.

Female CD1 rats weighing 250-300 g were anesthetized with ip pentobarbital, 50 mg/kg, and either the liver or the hindlimbs were surgically isolated and perfused in situ with a Krebs-Henseleit buffer, pH 7.4, at 38 degrees C, containing 40 g/liter dextran and 30 mg/liter papaverine. Perfusion pressure was continuously monitored, and in most experiments, flow was maintained at the physiological rate of 8.5 ml/min. In-line Clark-type electrodes allowed the continuous measurement of oxygen extraction. Potassium cyanide to 0.15 mM was usually added to the perfusate just prior to the start of a run. After a period of equilibration, samples of the perfusate were taken periodically for cyanide (CN) and thiocyanate (SCN) analyses. The results were used to determine CN extraction ratios or clearance and rates of SCN formation. When it was apparent that a steady state had been reached with respect to the above, sodium thiosulfate (TS) was added to the perfusate (to 0.1, 1.0, or 2.0 mM), and periodic samples were again collected after an equilibration period. In the absence of albumin, TS rapidly and significantly increased the rate of conversion of CN to SCN in both the liver and the hindlimbs. The rate of CN clearance in milliliters per minute per kilogram perfused tissue was 20-fold greater in the liver than in the hindlimbs. However, when the results from hindlimbs were extrapolated to the total body skeletal muscle mass, the rate of CN clearance by the total liver mass was only 1.5-fold greater than in total muscle mass. In the absence of TS, total muscle mass cleared CN at a rate that was 2.6-fold greater than the total liver mass, but the rates in both tissues were very much less than in the presence of TS. The extraction ratio for CN in the liver was 0.8 and the clearance was dependent on the flow rate. The extraction ratio for CN in the hindlimbs was 0.2, and the clearance was independent of the flow rate. Thus, CN clearance by the liver probably increases (within limits) with increasing portal blood flow. Evidence was obtained for the existence of a significant CN "sink," particularly in the liver, which presumably represents reversible binding to unknown tissue constituents.

Animals↗

PubMed1992

Intraperitoneal cisplatin chemotherapy in ovarian carcinoma patients who are clinically in complete remission.

Three courses of intraperitoneal cisplatin chemotherapy with systemic thiosulfate protection were administered to 31 stage II-IV ovarian carcinoma patients who were clinically in complete remission after completion of postoperative cisplatin-based combination chemotherapy. The 5-year survival rate was 60.4% and the median progression-free interval 35 months. Among 25 patients who underwent second-look laparotomy, the survival and the duration of the progression-free interval were significantly better in those with a pathologically confirmed complete response. Short-term intraperitoneal cisplatin chemotherapy should be considered for consolidation of treatment in ovarian carcinoma patients who are clinically in complete remission.

Adult↗

PubMed1983

The inhibition of rhodanese by lipoate and iron-sulfur proteins.

A study was made on the effects of DL-dihydrolipoate, lipoate and iron-sulfur proteins on the activity of rhodanese (EC 2.8.1.1) with dihydrolipoate or cyanide as acceptors. DL-Dihydrolipoate inactivates rhodanese, lipoate does not, and the opposite occurs with the sulfur-free form of the transferase. The observed effects vary with the sulfane sulfur acceptor from rhodanese (i.e., dihydrolipoate or cyanide) and depend on intramolecular oxidation of the catalytic sulfhydryl or on formation of a mixed disulfide with dihydrolipoate. Thiosulfate protects against inactivation by reloading the active-site cysteine with persulfide sulfur. The inhibition of sulfur transfer by iron-sulfur proteins appears related to the amount of native iron-sulfur structure interacting with rhodanese. The implications of the results for a possible biological role of rhodanese are considered.

Animals↗

PubMed1990

A physical characterization of sulfane sulfurtransferase.

The bacterial enzyme sulfane sulfurtransferase has been studied using spectroscopic techniques. The enzyme was characterized in terms of its near-UV absorption spectrum, molar ellipticity, intrinsic fluorescence spectra and the effects of general and ionic quenching reagents upon its fluorescence. Fluorescence model studies are consistent with sulfane sulfurtransferase having only a single tryptophan residue, which accounts for its low UV absorption coefficient and suggested that this residue is at least partially exposed to solvent. Second derivative absorption spectroscopy studies revealed that most of the bacterial enzyme's tyrosine residues are exposed to solvent. Unlike the better known sulfurtransferase, bovine liver rhodanese, sulfane sulfurtransferase does not undergo a detectable increase in quantum yield when shifting from the sulfur-containing covalent enzyme intermediate to the free enzyme form (which lacks sulfur) during catalysis. CD studies suggest that sulfane sulfurtransferase has a significantly higher proportion of alpha-helix than rhodanese. The renaturation of sulfane sulfurtransferase denatured in 6 M guanidine was shown to be rapid and complete provided that the enzyme had not been oxidized while in the denatured state. Sulfane sulfurtransferase, like rhodanese, catalyzes the transfer of sulfur from thiosulfate to cyanide via a persulfide intermediate, and displays remarkably similar kinetics in this process (Aird, B.A., Heinrikson, R.L. and Westley, J. (1987) J. Biol. Chem 262, 17327-17335). In light of this, the results of the structural studies with sulfane sulfurtransferase are compared and contrasted to data from similar experiments with rhodanese in hopes that they would provide insight about which phenomena observed with rhodanese are intrinsic to the process of transferring sulfur atoms.

Acinetobacter↗

PubMed1988

Sulfur isotope effects associated with oxidation of sulfide by O2 in aqueous solution.

Normal sulfur isotope effects averaging epsilon = -5.2 +/- 1.4% (s.d.) were consistently observed for the oxidation of sulfide in aqueous solution. Reaction products were sulfate, thiosulfate and sulfite at pH 10.8-11 in distilled water; S0 was formed in two experiments with synthetic seawater at pH 8-9.5. Because the -5.2% normal isotope effect differs significantly from the previously measured +2% inverse effect associated with anaerobic oxidation of sulfide by photosynthetic bacteria, stable sulfur isotopic measurements are potentially useful for distinguishing aerobic vs. anaerobic sulfide oxidation in marine and freshwater sulfureta.

Bacteria, Anaerobic↗