Thiols effect

Chong, S., Fung, H-L., Biochemical and pharmacological interactions between nitroglycerin and thiols. Effects of thiol structure on nitric oxide generation and tolerance reversal. Biochem. Pharmacol. 42 (1993), p. 1433-1439... 

Reduction of RX to RH.1 In the presence of di-r-butylhyponitrite (initiator) and a thiol,2 triethylsilane reduces alkyl chlorides, bromides, or iodides to alkanes in >91% yield by a chain reaction in which the thiol effects transfer of H from the silane to an alkyl radical. This reduction is generally effected with a R3SnH, which is toxic and more difficult to remove from the products. 

Metal ions of higher oxidation states, such as Fe , Ce, Co and oxidize thiols effectively... 

Venkatraman A, Landar A, Davis AJ, Ulasova E, Page G, Murphy MP, Darley-Usmar V, Bailey SM. Oxidative modification of hepatic mitochondria protein thiols Effect of chronic alcohol consumption. Am J Physiol Gastrointest Liver Physiol 2004 286(4) G521-7. 

Kondo T, Murao M, Taniguchi N (1982) Glutathione S-conjugate transport using inside-out vesicles from human erythrocytes. Eur J Biochem 125 551 Lu SC, Kuhlenkamp J, Ge JL, Sun WM, Kaplowitz N (1994) Specificity and directionality of thiol effects on sinusoidal glutathione transport in rat liver. Mol Pharmacol 46 578-85... 

Apart from domain boimdaries, some of the defects in alkanethiol monolayers (pitholes) are created by the thiol itself 159] by etching processes. It was found that the solvent used for preparation also has some effect on the resulting defect density. 

Steric effects of the substituents in positions 4 and 5 cannot shift the protomeric equilibrium sufficiently to permit spectroscopic observation of the thiol form (43b) ultraviolet spectra of 4-terr-butyl-5-methyl-A-4-thia2oline-2-thione (49a) in neutral solvents do not reveal any trace of the thiol protomer (49bi (Scheme 21) (70). 

The molecular weight of a polymer can be controlled through the use of a chain-transfer agent, as well as by initiator concentration and type, monomer concentration, and solvent type and temperature. Chlorinated aUphatic compounds and thiols are particularly effective chain-transfer agents used for regulating the molecular weight of acryUc polymers (94). Chain-transfer constants (C at 60°C) for some typical agents for poly(methyl acrylate) are as follows (87) ... 

Meta.1 Complexes. The importance of Ni complexes is based on their effectiveness as quenchers for singlet oxygen. Of disadvantage is their low colorfastness and their lower ir-reflectance compared to cyanine dyes (qv) therefore they are used in combination with suitable dyes. Numerous complexes are described in the Hterature, primarily tetrathiolate complexes of Pt or Ni, eg, dithiolatonickel complexes (3). Well known is the practical use of a combination of ben2othia2ole dyes with nickel thiol complexes in WORM disks (Ricoh, TDK) (17). 

Because thiols are easily oxidized, a host of organic and inorganic oxidants may be used. Mild oxidants such as oximes, nitro compounds, or air can be effective. Various oxidants have been used in special appHcations, but only a few are used in large-scale appHcations. 

Diisocyanates or Polyisocyanates. The thiol end groups of the hquid polysulfides are quite reactive with isocyanates (eq. 3). Typical chisocyanates, such as 1,3-toluene chisocyanate (m-TDl) and diphenylmethane-4,4 -diisocyanate (MDl), ate effective in curing hquid polysulfides. Using hquid polysulfides in-... 

The outcome of rapid radiation chemical processes in mammalian cells is to cause a variety of longer-Hved physical alterations in the DNA. Of these, double-strand breaks (DSBs) appear to be most frequently involved in cell killing if not correctly repaired. In general, thiols protect against DSB induction in proportion to their effect on cell killing (7), although there are exceptions (8). 

Modulation of the Killing of Mammalian Cells by Thiols. Important aspects of the effects of exogenous thiols on clonogenic cell survival following exposure to low linear energy transfer (LET) radiations include the following. 

Phosphorothioates generally protect normal tissues more than tumors. Tumor protection reported in some animal studies can pardy be explained by physiological effects of the particular dmgs, which are specific to rodents (4). WR-2721 does not appear to protect human and most animal tumors, apparentiy because of the low availabiUty of the dmg to tumor cells (4). Many tumors appear to have a reduced capillary density (44), which may mean that these tumors have altered levels of alkaline phosphatase, the enzyme that converts WR-2721 to WR-1065. A reduced abiUty of thiols to protect the hypoxic cells characteristic of many tumors may also contribute to their selectivity for normal tissues. The observation that WR-1065 protects cultured normal human fibroblasts, but not fibrosarcoma tumor cells, suggests that additional factors may contribute to the selectivity of radioprotection by WR-2721 m vivo (18). 

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