Sulfur and Halogenated Compounds

Incubation of liver microsomes with [ S]parathion results in radiolabeling of the protein but no radiolabeling occurs when the parathion ethyl groups are labeled with - . Ninety percent of the S-label, bound covalently to the microsomal proteins is immunoprecipitated 

CYP2C9 site that is modified by tienilic acid has not been identified, but HPLC/electrospray mass spectrometric (ESI-MS) analysis of the tienilic acid-modified and native proteins reveals the presence of mono- tmd diadducted CYP2C9 species with molecular masses of 55,923 1.1 and 56,273 4.4 Da, respectively, which corresponds to mass shifts of 344.4 1.1 and 694 4.2 Da. Diadduct formation is abolished by the inclusion of GSH (10 mM), suggesting that the diadduct may result from modification of a second residue outside the active site. The mass shift in the CYP2C9 monoadduct is consistent with the binding of a monohydroxylated tienilic acid obtained either by thiophene ring oxidation or formation of a sulfoxide that resists dehydration.  

CYP2C19 inactivation suggests that it occurs within the active site of the enzyme. The inactivation follows classical mechanism-based inactivation criteria with the following kinetic parameters i/2max = 3-4 min, = 3.2 X lO s , K, = 97 p-M, = 37 L mol s, and partition 

Other noteworthy sulfur-containing mechanism-based inactivators include thiocyanates such as phenethyl isothiocyanate benzylisothio-cyanate , tert-butylisothiocyanatediallyl sulfide, and diallylsulfone derivatives 1,2-dithiole-3-thione , oltipraz, and its deriva-tives , sulforaphane , and thiosteroids.  

Chloramphenicol was among the first chlorinated mechanism-based P450 inactivators shown 

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His scheme of nomenclature for nitrogen compounds, and the names thio-, chloro-, etc, did become widespread, especially for sulfur and halogen compounds. 

Reduced pressure helium MIP-MS has also been used as a GC detector for the separation of phosphorus, sulfur, and halogenated compounds [106-108]. This plasma is particularly well suited to these applications as air entrainment and subsequent high background signals are minimized. Again, heated stainless steel transfer lines are commonly used to connect the GC column to the ICP torch. 

Nearly 1000 compounds have so far been identified in the volatile constituents of meat from beef, chicken, mutton and pork (6). The largest number of volatiles has been determined in beef and these were representative of most classes of organic compounds. Hydrocarbons, alcohols, aldehydes, ketones, carboxylic acids, esters, lactones, ethers, sulfur and halogenated compounds as well as different classes of heterocyclic substances (Figure 1) namely furans, pyrldlnes, pyrazines, pyrroles, oxazol(in)es, thiazol(in)es, thiophenes were present in cooked meat flavor volatiles as shown in Table I. Many of these compounds are unimportant to the flavor of meat and some may have been artifacts (16). 

The malodorous Biflustra perfragllls which occurs in Bass Strait, the body of water which separates Tasmania from mainland Australia, has been found to give rise to a series of volatile sulfur and halogen compounds,56-61, [26] as well as alkaloids (see Section 2.3.4). Local fishermen are familiar with this bryozoan and its smell since they occasionally encounter it when dredging for scallops. The region where... 

Higher starting material purities are being achieved by the use of guard catalysts that remove catalyst poisons such as sulfur and halogen compounds, metals, and organic impurities. Here the zeolites have advantages over conventional adsorbents such as activated carbons [8]. 

Fig. 1 Optimized ground slate geometries (B3LYP/6-311 + G(d)) of some selected sulfur and halogen compounds (Reprinted with permission from [350]. Copyright 2011 IGI Global)...

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