Sulfhydryl acetic acid

Modifiers in the flotation of sulphide minerals mainly include depressants and activators. A depressant is defined as a reagent which inhibits the adsorption of a collector on a given mineral or adsorbed on the mineral to make the siuface hydrophilic, and includes inorganic depressants such as lime, sodium cyanide, sulphin dioxide, zinc sulphate, sodium sulphide etc., and organic depressants such as sulfhydryl acetic acid, polyacrylamide polymers containing various functional groups etc. In this chapter, roles of depressants in the flotation sulphide minerals will be discussed and some new organic depressants will be introduced. 

Because of the results found with p-(chloromercuri)benzoate and because /3-galactosidase is believed to be a sulfhydryl enzyme, it seemed advisable to investigate the effects of other sulfhydryl reagents. Virtually no inhibition of /3-galactosidase was found in the presence of iodoacetam-ide (9 X 10 M) over a period of 7 hours. A -Phenylmaleimide, at concentrations as high as 8.7 X 10 M, produced less than 10 % inhibition over a 20-hour period. However, when the concentration of V-phenyl-maleimide was raised to 9.1 X 10 M, assay of the incubation mixture revealed that 50% inhibition of /3-galactosidase occurred within a 2-hour period when the experiment was performed in 2-amino-2-(hydroxymethyl)-1,3-propanediol— acetic acid buffer, pH 8.0. Virtually no activity was lost when the latter experiment was repeated in phosphate buffer (Na salts) at the same pH. 

Acetyl chloride [75-36-5], C H OCl, mol wt 78.50, is a colodess, corrosive, irritating liquid that fumes in air. It has a stifling odor and reacts very rapidly with water, readily hydrolyzing to acetic acid and hydrochloric acid. As little as 0.5 parts per million activate the flow of tears, and often provoke a burning sensation in the eyes, nose, and throat. Acetyl chloride is toxic. Its high reactivity with hydroxyl, sulfhydryl, and amine groups leads to modifications that block the action of many important enzymes needed by living tissue. 

Actual compound formation also occurs between the dehydroascorhic acid and GSH reactants, though little attention has been paid to this condensation. Complexes of dehydroascorhic acid with one molecule of either GSH or thioglycolic acid were formed by Drake et al. (D19) in acetic acid solutions. Disappearance of iodine-titrable -SH groups and appearance of a new levorotatory material indicated the complex formation. This continued until an equilibrium was reached in about one hour at 0°C. At equilibrium more than half the dehydroascorhic acid was complexed. Remarkably little reduction of dehydroascorhic by the sulfhydryl compound occurred, since this reaction becomes significant only at neutral pH s. The complex is probably a thiosemiacetal, similar to... 

The sulfhydryl group of coenzyme A plays an important role in the biosynthesis of fatty acids from units of acetic acid. The key steps are suggested to be carboxylation with carbon dioxide of acetyl coenzyme A (which is a thioester 0 II... 

Acetic acid itself (acetate ion) cannot enter the citric acid cycle. It was discovered in 1950 by the American biochemist Fritz Lipmann (born 1899) that the form in which it does enter the cycle is as a compound with a complex substance called coenzyme A, abbreviated as CoASH (it contains the sulfhydryl group SH). The compound is acetyl-... 

Balasimha D, Ram G, Tewari MN (1977) Cytokinin-coumarin interaction in relation to growth, sulfhydryl, chlorophylls, and peroxidase-activity in Phaseolus radiatus L. seedlings. Biochem Physiol Pllanz 171 49-54 Ball NG, Dyke IJ (1956) The effects of indoie-3-acetic acid and 2 4-dichlorophenoxyacetic acid on the growth rate and endogenous rhythm of intact Avena coleoptiles. J Exp Bot7 25-41... 

The chloroketone reactive sulfhydryl group in the glutamine binding site of carbamyl phosphate synthetase reacts also with cyanate. " However, the inactive cyanate-enzyme complex regains activity upon incubation at alkaline pH. An S-[ C]carbamylcysteine derivative was isolated from the [" C] cyanate-enzyme complex after digestion with Pronase. S-Carbamyl cysteine moves with 22/ = 0.17 in butanol-acetic acid-water (12 3 5, v/v). 

Coenzyme A can form high-energy bonds with acetic acid via its sulfhydryl group to yield acetyl-coenzyme A (acetyl-CoA), also referred to as activated acetate. Through a variety of biochemical sequences, CoA can also be converted to a number of other acyl-CoA derivatives, such as malonyl-CoA, methylmalo-... 

N,0-Bis(dibenzosuberyl)-L-serine hydrochloride allowed to stand 6 hrs. at room temp, in 1 N HCl-dioxane N-dibenzosuberyl-L-serine. Y 79%. - The N-pro-tective group can also be removed under mild conditions, e.g. by refluxing in dil. acetic acid or by catalytic hydrogenation. F. e., also protection of sulfhydryl and carboxyl groups, s. J. Pless, Helv. 59, 499 (1976). 

As already oudined, inhibition is essentially complete when caused by reagents that react with sulfhydryl groups (for example, p-chloro-mercuribenzoate, p-mercuribenzoate, o-iodosobenzoate, L-ascorbic acid silver, cupric, and mercuric ions iodine, and ferricyanide) this inactivation can be reversed to some extent by hydrogen sulfide and by cysteine. Lineweaver—Burk graphs have shown that the action of L-ascorbic acid is noncompetitive, and L-ascorbic acid acting in the presence of cupric ions probably causes formation of an inactive cuprous-enzyme. The action of p-chloromercuribenzoate on barley beta-amylase has been shown to be a competitive inhibition. In contrast, the soya-bean p-chloromercuribenzoate inhibition is noncompetitive, and the extent of inhibition is inversely related to the concentration of acetate ion. The latter exhibits a protective effect, and there... 

The optimum temp for enzyme action is between 35° and 37° at pH 5-6. Lipase contains sulfhydryl groups and is inactivated by substances that inhibit such compels. It is activated by substances that keep SH groups in the reduced state, such as glutathione, cysteine, and ascorbic acid. The addition of acid activates lipase preparations. Castor-oil lipase is activated by sulfuric, oxalic, formic, acetic and butyric acids. Acetic, salicylic and hydrochloric acids increase the action of lipase derived from various Organs of the pig. Caprylic and caproic acids increase the action of lipase derived from certain mold tungi. Almost all organic solvents decrease lipase activity, patr ether being an exception. 

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