Disulfides mixed

Almost all cells contain a high concentration (3-9 mM) of the thiol-containing tripeptide glutathione (G-SH, Box 11-B). In its disulfide form it participates in forming disulfide bridges in secreted extracellular proteins (Eq. 10-9) via intermediate mixed disulfides. Mixed disulfides with glutathione as well as with other thiols can also be formed within cells by oxidative... 

These facts were successfully used to produce Mo—W alloys directly from the corresponding disulfide mixed crystals ... 

Halphen Reaction. The halphen test is a very sensitive and reliable method for detecting the presence of cottonseed oil in another oil. A reaction with sulfur in carbon disulfide mixed with equal amounts of amyl alcohol gives a cherry red color when cyclopropenoid fatty acids unique to the Malvacae family, which includes cottonseed and okra, are present. This test is capable of detecting 0.25% or less cottonseed oil in an oil blend. The oil is no longer responsive to the halphen test after hydrogenation, which decreases the iodine value 2-5 units. 

The calculations for the improved formula potassium nitrate 35% is a disulfide mix 35 / 67 = 0.5223. Sulfur — x 18 = 4.0 charcoal — x 10 = 2.2. Total charcoal required is 8.5%. The 9% in the formula is ideal as it allows for ash and water content. Total sulfur requirement is 14.9%, since the formula only has 9 and some of the sulfur in the antimony sulfide must be used to satisfy this. 5.9% x 3.53 = 20%. The formula is short of total disulfide character by 7% antimony or about 2% sulfur, and that is close enough Remember, the formula was arrived at empirically. Dropping the dextrin to 5% and adding 2% sulfur does improve the formula very slightly. 

Alkali Treatment. Caustic washing is the treatment of materials, usually products from petroleum refining, with solutions of caustic soda. The process consists of mixing a water solution of lye (sodium hydroxide or caustic soda) with a petroleum fraction. The treatment is carried out as soon as possible after the petroleum fraction is distilled, since contact with air forms free sulfur, which is corrosive and difficult to remove. The lye reacts either with any hydrogen sulfide present to form sodium sulfide, which is soluble in water, or with mercaptans, foUowed by oxidation, to form the less nocuous disulfides. 

When DMSO is mixed with concentrated hydrochloric acid, protonated DMSO is in equiUbtium with the chlorodimethylsiilfonium ion. Pummerer reactions and subsequent reaction of the initial products give a complex mixture of products including formaldehyde, bis(methylthio)methane, methanethiol, dimethyl disulfide, dimethyl sulfide, and others. 

Titanium trisulfide [12423-80-2], TiS, a black crystalline soHd having a monoclinic stmcture and a theoretical density of 3230 kg/m, can be prepared by reaction between titanium tetrachloride vapor and H2S at 480—540°C. The reaction product is then mixed with sulfur and heated to 600°C ia a sealed tube to remove residual chlorine. Sublimatioa may be used to separate the trisulfide (390°C) from the disulfide (500°C). Titanium trisulfide, iasoluble ia hydrochloric acid but soluble ia both hot and cold sulfuric acid, reacts with concentrated nitric acid to form titanium dioxide. 

The thiol form (12) is susceptible to oxidation (see Fig. 2). Iodine treatment regenerates thiamine in good yield. Heating an aqueous solution at pH 8 in air gives rise to thiamine disulfide [67-16-3] (21), thiochrome (14), and other products (22). The disulfide is readily reduced to thiamine in vivo and is as biologically active. Other mixed disulfides, of interest as fat-soluble forms, are formed from thiamine, possibly via oxidative coupling to the thiol form (12). 

Sulfides orthio derivatives Metallic derivatives of thio ethers and disulfides, usually mixed with organic phosphite esters long-chain alkyl thienyl ketones Lubricating oils boiler water... 

In a 2-1. round-bottomed flask are placed 120 g. (1.83 moles) of 92% ethylenediamine (Note 1), 300 ml. of 95% ethanol, and 300 ml. of water. The flask is attached to an efficient reflux condenser, and 121 ml. of carbon disulfide is placed in a separatory funnel attached to the top of the condenser by means of a notched cork. About 15 to 20 ml. of the carbon disulfide is added, and the flask is shaken to mix the contents. A vigorous reaction takes place (Note 2), and it may be necessary to cool the flask. After the reaction has started, a water bath at 60° is placed under the flask and the balance of the carbon disulfide is added at such a rate that the vapors reflux about one-third the way up the condenser. About 2 hours are required for the addition of the carbon disulfide. At this time the bath temperature is raised to about 100°, and the mixture is allowed to reflux for 1 hour. Then 15 ml. of concentrated hydrochloric acid is added, and the mixture is refluxed under a good hood (bath at 100°) for 9 to 10 hours. The mixture is cooled in an ice bath, and the product is filtered by suction on a Buchner funnel and washed with 200-300 ml. of cold acetone (Note 3). A yield of 156-167 g. (83-89%) of white crystals is obtained melting at 197-198° (Note 4). 

The C-terminal domain of phosducin is a five-stranded mixed p sheet with a helices on both sides, similar to the thioredoxin fold of disulfide iso-merase DsbA described in Chapter 6. Despite significant sequence homology to thioredoxin, the phosducin domain, unlike other members of this family. 

II. Thiol oxidants cystaminc (mixed disulfide formation), diamide, t-BHP, menadione, diquat... 

In addition to classification based on layer structure, proteins can be grouped according to the type and arrangement of secondary structure. There are four such broad groups antiparallel a-helix, parallel or mixed /3-sheet, antiparallel /3-sheet, and the small metal- and disulfide-rich proteins. 

The special properties of lipoic acid arise from the ring strain experienced by oxidized lipoic acid. The closed ring form is approximately 20 kj higher in energy than the open-chain form, and this results in a strong negative reduction potential of about —0.30 V. The oxidized form readily oxidizes cyanides to isothiocyanates and sulfhydryl groups to mixed disulfides. 

Figure 12.12 Coupled SEC-RPLC separation of Plioflex rubber stock (a) SEC (b) RPLC ti ace of fraction 1, Wingstay 100 (Eive-peak pattern is representative of diarylphenylenedi-amine isomers) (c) RPLC ti ace of fraction 2, mixed disulfide and MBTS (2,2 -thiobis (ben-zothiazole)). Obtained under the same conditions as given for Eigure 12.11. Reprinted from Journal of Chromatography, 149, E. L. Johnson et al, Coupled column chromatography employing exclusion and a reversed phase. A potential general approach to sequential analysis , pp. 571-585, copyright 1978, with permission from Elsevier Science.

Methane reacts with sulfur (an active nonmetal element of group 6A) at high temperatures to produce carbon disulfide. The reaction is endothermic, and an activation energy of approximately 160 KJ is required. Activated alumina or clay is used as the catalyst at approximately 675°C and 2 atmospheres. The process starts by vaporizing pure sulfur, mixing it with methane, and passing the mixture over the alumina catalyst. The reaction could be represented as ... 

The sweetening process utilizes a caustic solution, catalyst, and aii. Mercaptans are converted to disulfides in a mixing vessel or fiber film contactor. The reactions take place according to the following equations... 

The mixture of caustic and disulfides is transferred to a settler. From the settler, the treated gasoline flows to a coalescer, sand filter, or wash water tower, before going to storage. The caustic solution is recirculated to the mixing vessel/fiber film contactor. 

N204 also forms expl mixts with incompletely halogenated hydrocarbons, NGu, carbon disulfide, etc (Ref 33). The effect of spontaneous decompn by oxidation-reduction reactions when N204 is mixed with a number of fuels (hydrazine, gasoline, liq paraffin, etc) has resulted in its extensive use in liq propint rocket engines (Refs 12, 22, 27 35)... 

Nordenfelt and Meurling Powder. A propint, patented in Engl in 1884, prepd as follows Cotton or other cellulosic material, was transformed into a material resembling hydrocellulose thru treatment with hydrochloric acid. It was then dried, pulverized, and mixed with S disd in carbon disulfide. After evapn of the CS2, the material was treated with a coned soln of K nitrate, granulated and dried Ref Daniel (1902), 583... 

The yellow disulfide radical anion and the briUiant blue trisulfide radical anion often occur together for what reason some authors of the older Hterature (prior to 1975) got mixed up with their identification. Today, both species are well known by their E8R, infrared, resonance Raman, UV-Vis, and photoelectron spectra, some of which have been recorded both in solutions and in solid matrices. In solution these radical species are formed by the ho-molytic dissociation of polysulfide dianions according to Eqs. (7) and (8). 8ince these dissociation reactions are of course endothermic the radical formation is promoted by heating as well as by dilution. Furthermore, solvents of lower polarity than that of water also favor the homolytic dissociation. However, in solutions at 20 °C the equilibria at Eqs. (7) and (8) are usually on the left side (excepting extremely dilute systems) and only the very high sensitivity of E8R, UV-Vis and resonance Raman spectroscopy made it possible to detect the radical anions in liquid and solid solutions see above. 

RSS 2 was mixed with N-234 carbon black without additive or in the presence of quinonedihne, or with a peptizer (dibenzamidodiphenyl disulfide, activated with a metal chelate). In the case of the peptizer, rubber and carbon black were mixed for 30 s before the addition of carbon black. In the case of the quinone diimine, carbon black and QDI were added 15 s after addition of rubber to the mixer. 

The change in Mooney viscosity is plotted as a function of turns of the mixer (i.e., rpm X cummulative minutes of mixing). The results are presented in Figures 16.2 and 16.3. Under the LTM conditions httle discrimination is observed between triplicate batches of the control (no additive) and the batches containing disulfidic peptizer. However, even under the LTM condition. 

FIGURE 16.12 Mooney viscosity at 175°C of butadiene elastomer mill mixed with 50 phr of N-234 10 phr of naphthenic oil with the labeled loading of a commercial peptizer (diphenyl dibenzamido-disulfide). 

There are numerous abnormalities of cysteine metabolism. Cystine, lysine, arginine, and ornithine are excreted in cystine-lysinuria (cystinuria), a defect in renal reabsorption. Apart from cystine calculi, cystinuria is benign. The mixed disulfide of L-cysteine and L-homocysteine (Figure 30-9) excreted by cystinuric patients is more soluble than cystine and reduces formation of cystine calculi. Several metabolic defects result in vitamin Bg-responsive or -unresponsive ho-mocystinurias. Defective carrier-mediated transport of cystine results in cystinosis (cystine storage disease) with deposition of cystine crystals in tissues and early mortality from acute renal failure. Despite... 

Kamura T Tsuda H., Yae Y., et al. An abnormal fibrinogen Fukuoka II (Gly-B(315- CY5) characterized by defective fibrin lateral association and mixed disulfide formation. J Biol Chem 1995 270,29392-9. 

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