Chloramines reactions with amino acids

The other amino acid reacting with HOC1 is tyrosine. At pH ranging from 3.5 to 6.0, HOC1 reacts with A-acetyltyrosine to produce S -chloro derivative (Fig. 8). If the HOCl/N-acetyltyrosine molar ratio exceeds 10, 3/5/-dichlorotyrosine formation is observed. The chlorotyrosine formation is slow compared to chloramine formation or tryptophan oxidation reaction rate. The optimal conditions for tyrosine... 

Free amino acids readily form chloramines in reactions with HOC1. However, the reaction can be postponed by the presence of amino acids whose side groups have reducing properties (as is the case with cysteine, methionine, and tryptophan). Amino acid chloramines located at the a-carbon are unstable, decomposing by deamination and decarboxylation. The final stable products are ammonia, chloride, and the aldehyde respective to the amino acid carbon backbone (H12, Z4) ... 

If a peptide contains Tyr, it is possible to iodinate this amino acid residue with 125I in the ortho position relative to the hydroxy group. This is effected by reaction of the peptide with Na125I in the presence of chloramine-T. If a known amount of the labelled peptide (P ) is allowed to compete with a measured volume of a solution containing an unknown concentration of unlabelled peptide (P) for a known limited amount of antibody (Ab) raised to the unlabelled peptide there will be a competition for the antibody binding sites ... 

SuperchlorinationShock Treatment. Superchlorination or shock treatment of pool water is necessary since accumulation of organic matter, nitrogen compounds, and algae consumes free available chlorine and impedes disinfection. Reaction of chlorine with constituents of urine or perspiration (primarily NH" 4, amino acids, creatinine, uric acid, etc) produces chloramines (N—Cl compounds) which are poor disinfectants because they do not hydrolyze significantly to HOCl (19). For example, monochloramine (NH2CI) is only 1/280 as effective as HOCl against E. coli (20). 

Amino-Hydroxylation. A related reaction to asymmetric dihydroxylation is the asymmetric amino-hydroxylation of olefins, forming v/c-ami noalcohols. The vic-hydroxyamino group is found in many biologically important molecules, such as the (3-amino acid 3.10 (the side-chain of taxol). In the mid-1970s, Sharpless76 reported that the trihydrate of N-chloro-p-toluenesulfonamide sodium salt (chloramine-T) reacts with olefins in the presence of a catalytic amount of osmium tetroxide to produce vicinal hydroxyl p-toluenesulfonamides (Eq. 3.16). Aminohydroxylation was also promoted by palladium.77... 

The exceptions are chloramines of valine, leucine, and isoleucine, which form semistable chloramines that remain in the reaction medium for several hours (Z4). The mechanism of aldehyde formation from the intermediary amino acid a-chloramines produced either by HOC1 treatment or by the MP0-H202-C1- system was recently verified with use of NMR spectra. The study made possible the identification of short-lived products of the reaction, and confirmed the role of the unstable monochloramine of the a-amino group as the intermediate (H12). 

Amino-substituted (quasi-phosphonium) derivatives are produced in reaction (6.373) and by reaction of tertiary phosphines with chloramine or hydrazoic acid (6.104,6.105), or by the reaction of phosphonous diamides with chloramine or alkali metal halides (7.196). 

Breakpoint chlorination. Breakpoint chlorination is a historical concept where combined chlorine is reoxidized to hypochlorous acid by the addition of an excess concentration of hypochlorous acid. These are collectively referred to as combined chlorine or combined available (CAC) under the assumption that the chlorine can be re-liberated. The model used for nearly all literature cites the interaction between hypochlorous acid and ammonia. In recreational water the amount of hypochlorous acid used for a breakpoint treatment is normally ten times the concentration of the combined chlorine. However, the reaction between hypochlorous acid and more complex nitrogen compounds is not fully reversible. White (1986) showed that breakpoint water containing a mixture of combined chlorine from organic and simple ammonia failed to display the elassic dip of the breakpoint reaction. These waters displayed a plateau concentration below which no further reduction in combined chlorine occurred. The nitrogen compounds in recreational water are introduced in bather waste and from the environment and contain mostly amino acids, peptides, and proteins with little free ammonia. Practical experience has shown that this method will reduce, but not eliminate, the combined chlorine. If repeated breakpoint treatments fail to reduce the combined chlorine to the target level (0.02 to 0.05 ppm CAC) alternate treatments such as oxidation with a potassium monopersulfate or partial water replacement to dilute the chloramines must be used. 

To prepare the diborane in tetrahydrofuran, add 0.3 M NaBH4 (or LiBH4) and 0.4 M BF3 in total 200 ml tetrahydrofuran and keep dry in refrigerator, or generate the diborane in the reaction flask as follows To a well-stirred suspension of 3.4 g NaBH4 in 150 ml tetrahydrofuran and 0.3M of the styrene or propenylbenzene, add over one hour at room temperature, 15.1 ml BF3 in ether in 20 ml tetrahydrofuran (keep temperature at room temperature) let stand one hour at room temperature and decompose the excess hydride with water then add the NaOH and chloramine (or hydroxyl-amino-O-sulfonic acid) and proceed as above to get the amine. 

Sulfonamides in mixtures have been determined by titration with 0.02 M chloramine-T after bromination. The ortho dibromination is prevented by acetylation of the aromatic amino group but the reaction of side-chain substituents remains unaffected. The relative standard deviations are about 1%. Interferences even in small amounts, from barbituric acid, isoniazid, ascorbic acid, methionine, thymol and penicillins are observed (33). 

If the antibody is immobilised on Sepharose , the supernatant containing the free, radioactive peptide can be separated easily and assayed in a gamma counter. With a standard curve drawn for known amounts of peptide subjected to assay under exactly the same conditions, unknown amounts of peptide can be determined by interpolation on the standard curve. There are two potential problems with this type of radioimmunoassay. First, the peptide to be assayed perhaps does not contain Tyr. If it contains His, however, this may suffice since His can be iodinated, especially by an enzymic procedure described below. Alternatively, the peptide is allowed to react with the Bolton and Hunter reagent (Bolton and Hunter, 1973), prepared by iodina-tion of the ester of 3-(4 -hydroxyphenyl)propionic acid and /V-hydroxysuccinimide. Any free amino group can be acylated by this reagent. Secondly, reaction of a peptide with Nal and chloramine-T can cause oxidation of Met, Cys and even Tyr residues, which can interfere with complexation of the iodinated peptide with antibodies raised to the un-iodinated peptide. An alternative method (Holohan et al., 1973) of iodination uses lactoperoxidase in the presence of H202. As pointed out above, this procedure is applicable to the iodination of His residues. This method avoids modification of the side-chains of Met, Cys and Tyr. 

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