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PubMed1991

Inhibition of the Clostridium perfringens phospholipase C hydrolysis of a thiophosphate analog of lysophosphatidylcholine by micelle-bound ammonium and sulfonium cations.

Cetyltrimethylammonium and n-octadecyldimethylsulfonium bromides inhibit the Clostridium perfringens phospholipase C-catalyzed hydrolysis of 1-S-phosphocholine-2-O-hexadecanoyl-1-mercapto-2-ethanol (1) at pH 7.5, 37 degrees C, mu = 0.15 with KCl. Mixed micelles containing 1 and either inhibitor are substrates for the enzyme and the fraction of activity remaining is a monotonic, but non-linear function of the mole fraction of inhibitor. Simple saturation kinetics are observed as the concentration of 1 is increased in mixed micelles containing a constant mole fraction of inhibitor. Inhibition constants for cetyltrimethylammonium and n-octadecyldimethylsulfonium bromides are 0.66 +/- 0.04 and 0.25 +/- 0.02 mM, respectively. The data suggest that the significant inhibition previously observed for soluble alkyldisulfonium salts (K50 for dodecamethylene-bis(dimethylsulfonium) bromide, 27 microM) is dependent upon bifunctional cationic interactions rather than hydrophobic binding.

Cations↗
PubMed1985

An essential tryptophan residue for rabbit muscle creatine kinase.

The tryptophan residues in rabbit muscle creatine kinase (ATP:creatine N-phosphotransferase, EC 2.7.3.2) have been modified by dimethyl(2-hydroxy-5-nitrobenzyl) sulfonium bromide after reversible protection of the reactive SH groups. The modification of two tryptophan residues as measured by spectrophotometric titration leads to complete loss of enzymatic activity. Control experiments show that reversible protection of the reactive SH groups as S-sulfonates followed by reduction results in nearly quantitative recovery of enzyme activity. The presence of a 410 nm absorption maximum and the decrease in fluorescence of the modified enzyme indicate the modification of tryptophan residues. At the same time, SH determinations after reduction of the modified enzyme show that the reagent has not affected the protected SH groups. Quantitative treatment of the data (Tsou, C.-L. (1962) Sci. Sin. 11, 1535 1558) shows that among the tryptophan residues modified, one is essential for its catalytic activity. The presence of substrates partially protects the modification of tryptophan residues as well as the inactivation, suggesting that the essential tryptophan residue is situated at the active site of this enzyme.

Animals↗
PubMed1989

Effect of ionic charge on detergent-induced hemolysis.

7.0 microM Sodium dodecyl sulfate induces lysis on A Rh(+) red blood cells 1.6 times faster than the cationic analog dodecyl thiouronium chloride at 37 degrees C and pH = 7.30. Hemolysis isotherms show identical values for the Hill cooperativity parameters of the organic surfactants, but different dissociation parameters. The anionic detergent destabilizes red cell membranes more efficiently than the cationic analog, probably due to the predominance of negative charges on the erythrocyte membranes at physiological pH.

Animals↗
PubMed1987

Effect of permanently charged and uncharged dopaminergic agonists on the potassium-induced release of [3H]acetylcholine from striatal slices.

The effects of chemical analogs of dopamine, which are permanently charged or which lack a net positive charge, on the potassium-evoked release of [3H]acetylcholine from mouse striatal slices were studied in order to determine whether a positive charge on the dopamine agonist molecule is required to activate dopaminergic receptors. The striatal slices were first preincubated with [3H]choline, transferred to a superfusion chamber, and then superfused in physiological medium. [3H]Acetylcholine release was evoked by exposure of the slices to a high potassium medium and potential dopamine agonist drugs were added to the medium 10 min before superfusing with high potassium. A permanently charged quaternary ammonium analog and dimethylselenonium analog of dopamine inhibited the potassium-evoked release of [3H]acetylcholine, and this inhibition was antagonized by sulpiride, a dopamine receptor antagonist. However, this inhibition was not antagonized by reserpine and alpha-methyl-p-tyrosine, which was shown to completely antagonize the inhibitory effect of amphetamine, an indirectly acting amine. This suggests that the charged dopamine analogs are acting directly on dopaminergic receptors. In contrast to the permanently charged dopamine analogs, analogs of dopamine with no net positive charge produced no inhibition of the potassium-evoked [3H]acetylcholine release. These in vitro observations are in agreement with a behavioral model in which a permanently uncharged monomethylsulfide analog of dopamine was ineffective in eliciting circling behavior after its unilateral injection into the striatum of rats in which dopamine neurons were previously lesioned by the injection of 6-hydroxydopamine into the medial forebrain bundle. In contrast, under these same conditions, the intrastriatal injection of the charged quaternary ammonium or dimethylsulfonium analog of dopamine elicited intense contralateral circling. These results suggest that the charged form of a dopamine agonist molecule is required to bind to and activate the dopamine receptor regulating [3H]acetylcholine release and circling behavior.

Acetylcholine↗
PubMed1976

Effects of triphenylsulphonium ions on mitochondria. Inhibition of adenosine triphosphatase activity.

Triphenylsulphonium ions inhibit mitochondrial oxidative phosphorylation and adenosine triphosphatase activity. The site of action is on the soluble F1 adenosine triphosphatase component. Triphenylsylphonium ions also inhibit electron transfer in the NAD-cytochrome b region of the respiratory chain. In both types of inhibition, triphenylsulphonium ions are effective at low concentrations, half-maximal inhibition being produced by a concentration of about 20-30 muM. These effects resemble the effects of alkylguanidines on mitochondria and are discussed in relation to the effects of alkylguanidines and other lipophilic cations such as ethidium and dibenzyldimethylammonium ions. A modification of the purification procedure for the soluble mitochondrial adenosine triphosphatase [Beechey, Hubbard, Linnett, Mitchell & Munn (1975) Biochem. J. 148, 533-537] IS DESCRIBED, WHICH YIELDS A PREPARATION WITH A HIGHER SPECIFIC ACTIVITY AND SHOWING FEWER BANDS IN GEL ELECTROPHORESIS.

Adenosine Triphosphatases↗
PubMed2003

Study of organic sulphur compounds (DMS, DMSP and CS2) in lagoon ecosystems: the case of the Venice lagoon.

This study of the origin and fate of dimethyl sulphide (DMS) in a particular and complex lagoon ecosystem such as that of the Venice lagoon focuses on the temporal evolutions of DMS concentrations in surface water together with those of dimethylsulphoniopropionate (DMSP), carbon disulphide (CS2), nutrients (nitrate, nitrite, ammonium, phosphate, silicate), sulphate, chlorophyll a, chlorinity, water temperature and phytoplankton (composition and density). Measurements were made from 3 March 1997 to 23 July 1998 at three stations in the central part of the Venice lagoon. The temporal trends of DMS concentration showed an absolute maximum concentration in winter (65 nmol S/l, 19/2/1998, Stn. 1; 119 nmol S/l, 19/2/1998, Stn. 2; 29 nmol S/l, 17/2/1998, Stn. 3) and two relative maxima in the spring-summer period. The spring-summer secondary maxima of DMS concentration were related to the maxima of DMSP and chlorophyll a concentrations and consequently to phytoplanktonic abundance while the winter DMS maximum showed no relation to DMSP or to chlorophyll a suggesting that the production and the fate of DMS could be different for the two periods. According to previous studies the CS2 concentration increased in the spring, achieved its maximum in summer, decreased in autumn and fell to its minimum in winter.

Carbon Disulfide↗
PubMedDate not supplied

[Atranes: their ulcerostatic effect and its possible mechanisms].

The ulcerostatic activity of methylethyl (sylathrane-1-ilmethyl) sulfoiodide, 1-(chlormethyl) sylatrane, and 1-(isopropoxy)hermatrane has been revealed at experimental acetate ulcer in rats. The effect of atranes was equal to that of oxyferriscorbone and exceeded that of methyluracil. All the compounds studied inhibited peroxide oxidation of lipids in blood and stomach tissues from ulcer and in model experiments in egg yolk liposomes. The processes of ulcer development and photodynamic effects of lipid peroxidation in biological objects have been summarized. The data obtained allow to conclude that the ulcerostatic mechanism of action effect of atranes and the comparable drugs is based on their antioxidative effect.

Acetates↗
PubMed1985

Structure-nephrotoxicity relationships of S-(2-chloroethyl)-DL-cysteine and analogs: role for an episulfonium ion.

1,2-Dichloroethane produces kidney damage, but the mechanism is unclear. Cysteine conjugates, which could arise from S-(2-chloroethyl)glutathione or S-(2-chloroethyl)cysteine have been identified. In this study, rats given S-(2-chloroethyl)-DL-cysteine (100 mg/kg i.p.) showed significant increases in blood urea nitrogen and urine glucose concentrations. Histopathological examination of kidneys, 36 hr after treatment showed acute proximal tubular nephrosis and punctuate glomerular necrosis. No hepatic lesions were seen and serum glutamate-pyruvate transaminase activities were only elevated slightly. The extent of S-(2-chloroethyl)-DL-cysteine renal toxicity was dose- and time-dependent. Equimolar doses of analogs of S-(2-chloroethyl)-DL-cysteine, S-ethyl-L-cysteine, S-(2-hydroxyethyl)-N-acetyl-DL-cysteine, S-(2-hydroxyethyl)-DL-cysteine, or S-(3-chloropropyl)-DL-cysteine, failed to produce nephrotoxicity; rats given L-cysteine (100 mg/kg i.p.), S-ethyl-L-cysteine (100 mg/kg i.p.) or probenecid (60 mg/kg i.p.) 30 min before receiving S-(2-chloroethyl)-DL-cysteine had significant reductions of the S-(2-chloroethyl)-DL-cysteine-induced blood urea nitrogen and urine glucose elevations. These results show that S-(2-chloroethyl)-DL-cysteine is a potent, selective nephrotoxin that may be responsible for the renal damage associated with 1,2-dichloroethane. The formation of an episulfonium ion plays an important role in S-(2-chloroethyl)-DL-cysteine-induced nephrotoxicity. The protection against renal damage provided by S-ethyl-L-cysteine or probenecid may involve competition with S-(2-chloroethyl)-DL-cysteine for cellular or transport binding sites.

Acute Kidney Injury↗
PubMed1998

Modification of the reductive pathway in gamma-irradiated DNA by electron scavengers: targeting the sugar-phosphate backbone.

Several electron scavengers that irreversibly form potential hydrogen-abstracting species upon one-electron reduction have been tested as agents for conversion of reductive damage to DNA bases into damage to the sugar-phosphate backbone. Electron spin resonance spectroscopy is employed to follow the production of radicals and transformations after irradiation. The scavengers tested included neutral (acrylamide, iodoacetamide) and cationic [triphenylsulfonium (Ph3S+), o,o'-diphenylenebromonium (DPB) and o,o'-diphenyleneiodonium (DPI)] compounds. Modification of reductive radiation damage in DNA is found to occur by scavenging of initial mobile electrons at low temperatures as well as thermally activated electron transfer from DNA electron-gain centers upon annealing. Electron transfer from the bases to hydrogen-bonded acrylamide has the smallest activation energy among other scavengers but produces a secondary alkyl radical incapable of abstracting hydrogen from the sugar-phosphate backbone. A primary alkyl radical generated from iodoacetamide has been shown to abstract preferentially from the thymine methyl group but not from deoxyribose moieties. Aryl radicals generated from aromatic onium salts such as Ph3S+, and especially DPI and DPB, are found to be the agents which best abstract hydrogen atoms from the deoxyribose portion of DNA. The use of DPB and DPI as radiation modifiers allows the elimination of undesirable side reactions of aryl radicals and through hydrogen abstraction results in high yields of a species identified as the DNA C1'. sugar radical. The second reaction pathway found for DPI and DPB in DNA is addition of an aryl radical to the thymine 5,6 double bond. Cysteamine is shown to preferentially eliminate sugar radicals upon annealing and to have little impact on the thermal stability of the thymine adduct radical.

Acrylamide↗
PubMed1996

Suicide inactivation of thioether S-methyltransferase by ethyl sulfide.

Thioether S-methyltransferase is an important enzyme in the metabolism of sulfur and selenium-containing compounds in animals. Ethyl vinyl sulfide was previously shown to be a substrate for this enzyme yielding methyl ethyl vinyl sulfonium ion (MEVS+) upon reaction with S-adenosylmethionine. Since vinyl sulfonium ions are reactive toward nucleophiles, the inactivation of thioether S-methyltransferase as a result of its methylation of ethyl vinyl sulfide was investigated. Ethyl vinyl sulfide was found to inactivate thioether S-methyltransferase in a time-dependent, pseudo-first-order process with k(inact) and KI values of 0.05 min(-1) and 0.275 mM, respectively. Calculation of the partition ratio revealed one inactivation event for every 100 turnovers. Dimethyl sulfide, an alternate substrate for thioether S-methyltransferase which yields the nonreactive product trimethyl sulfonium ion, protected the enzyme from inactivation by ethyl vinyl sulfide. The inactivation is a result of covalent reaction of methyl ethyl vinyl sulfonium ion with the enzyme as shown by comigration of radioactivity with the enzyme during denaturing gel filtration of reaction mixtures containing thioether S-methyltransferase, ethyl vinyl sulfide, and S-adenosyl[methyl-3H]methionine. Using this method the stoichiometry of inactivation was determined to be 1 mol of [3H]-methyl group/mol of thioether S-methyltransferase inactivated. Both the alternate substrate, dimethyl sulfide, and the competitive product inhibitor, S-adenosylhomocysteine, inhibited such covalent labeling of the enzyme by ethyl vinyl sulfide and S-adenosyl[methyl-3H]methionine. Chemically synthesized MEVS+ inactivated thioether S-methyltransferase, and [methyl-14C]MEVS+ covalently labeled the enzyme with 14C. These results reveal a previously unrecognized mechanism for biochemical activation of vinyl thioethers by methylation to form reactive vinyl sulfonium ions.

Animals↗
PubMed2004

Dimethylsulphoniopropionate (DMSP) and related compounds in higher plants.

Dimethylsulphoniopropionate (DMSP) is produced in high concentrations in many marine algae, but in higher plants only in a few salt marsh grasses of the genus Spartina, in sugar canes (Saccharum spp.), and in the Pacific strand plant Wollastonia biflora (L.) DC. The high concentrations found in higher plants (up to 250 micromol g(-1) dry weight) suggest an important role, but though many functions have been suggested (including methylating agent, detoxification of excess sulphur, salt tolerance, and herbivore deterrent), its actual functions remain unclear. The fact that the ability to produce DMSP in high concentrations is found in species that have no taxonomic or ecological relationship suggests that the compound evolved independently and serves different functions in different plants. This is supported by observations that DMSP in W. biflora behaves differently from that in Spartina species. While DMSP concentrations in W. biflora have been found to increase with increasing salinity, suggesting a role in osmotic control, such a relationship has not been found for DMSP in Spartina species. Recent observations on tissue culture showed that, while undifferentiated tissue of W. biflora produced DMSP, such material of Spartina alterniflora Loisel. did not. Ongoing studies with tissue culture of both species have opened up new avenues of research on DMSP in higher plants, ultimately to elucidate the functions of this enigmatic compound.

Models, Chemical↗
PubMed2004

Asymmetric synthesis of cyclic alpha-amino phosphonates using masked oxo sulfinimines (N-sulfinyl imines).

Five-, six-, and seven-membered cyclic alpha-amino phosphonates, amino acid surrogates, are prepared in enantiomerically pure form via the highly diastereomeric addition of metal phosphonates to masked oxo sulfinimines. Hydrolysis of the resulting masked oxo alpha-amino phosphonates followed by reduction of the intermediate cyclic imino phosphonates affords the title compounds in good yield.

Amino Acids↗
PubMed2002

Winter evolution of DMS and DMSP in Venice lagoon water and sediment.

The evolution of dimethylsulphide (DMS) and dimethylsulphoniopropionate (DMSP) concentrations in the water and sediment of the Venice lagoon were studied together with the concentration of chlorophyll a, temperature and the composition and density of phytoplankton to understand the role of the sediment as a source of DMS during the winter period. The temporal trend of water DMS concentration in this period showed a maximum concentration in February (75.7 nmol S l-1) related to low DMSP and chlorophyll a concentrations but to high phytoplanktonic abundance. The DMS and DMSP concentrations were greater in the sediment than in the water. The temporal trend of DMS concentration in sediment showed a maximum in February (1155 nmol S l-1) related to the maximum of DMS concentration in surface water. These observations suggested that in the winter period DMS could be produced by the conversion of the DMSP present in the bulk water but principally by that present in the sediment (microbiological degradation of DMSP or other sulphur-containing compounds) that subsequently diffuse in water.

Chlorophyll↗
PubMed1977

Thioacetamide-induced hepatic necrosis. I. Involvement of the mixed-function oxidase enzyme system.

Metabolic activation of thioacetamide (CH3CSNH2) to a toxic metabolite which is responsible for its hepatotoxicity and/or its carcinogenicity has been proposed by a number of investigators. In this investigation thioacetamide and one of its metabolites, thioacetamide sulfine (CH3CSONH2), have been compared for their ability to inhibit hepatic mixed-function oxidase enzymes as well as their ability to induce hepatic necrosis. Thioacetamide sulfine was found to decrease aminopyrine N-demethylation and aniline hydroxylation at a lower dose and at an earlier time after administration than was the case with thioacetamide. In addition, at all doses examined, thioacetamide sulfine produced a more severe centrilobular hepatic necrosis than equivalent doses of thioacetamide. To determine whether the hepatic mixed-function oxidase enzyme system was involved in the biotransformation of thioacetamide and/or thioacetamide sulfine to a hepatotoxic compound(s), the severity of liver damage was examined after the administration of an inducer or inhibitors of hepatic mixed-function oxidase enzyme activity. Phenobarbital pretreatment potentiated the hepatic necrosis produced by both thioacetamide and thioacetamide sulfine. In contrast, pyrazole, SKF 525-A, and cobaltous chloride protected against the hepatic necrosis caused by thioacetamide and thioacetamide sulfine. These data suggest that both thioacetamide and thioacetamide sulfine are activated by hepatic mixed-function oxidase enzymes to a hepatotoxic compound(s). These data also suggest that the hepatotoxicity may be mediated by its metabolism to thioacetamide sulfine which, in turn, is metabolized to an ultimate toxic metabolite.

Acetamides↗
PubMed2004

Direct effects of high concentrations of dimethylsulfoniopropionate, vitamin E and ferulic acid on the senility of aged scenescene-accelerated mouse (SAMP8).

The effects of high concentrations of dimethylsulfoniopropionate (DMSP), vitamin E and ferulic acid solutions on the aging of male and female scenescene-accelerated mouse (SAMP8) at the age of 50 wk were examined by direct supplementation to their stomachs twice a week for 28-30 d. The addition of 1 mL of DMSP, vitamin E and ferulic acid solutions (21% each) to the male and female mice in each group in this order rather elevated their growth and significantly suppressed their total grading score and loss of learning and memory with increasing rearing times for the short experimental period. However, there were no significant differences found between the male and female mice during the experimental period. The antioxidant and hormonal actions for the effects of the test compounds on the aged SAMP8 were possibly considered.

Aging↗