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PubMed2001

An oxidation resistant radioligand for corticotropin-releasing factor receptors.

The methionine residues in Tyr-corticotropin-releasing factor (CRF) and Tyr-sauvagine radioligands are subject to oxidation, which renders them biologically inactive. Therefore [Tyr(0,) Gln(1,) Leu(17)]sauvagine (YQLS), in which the methionine was replaced with leucine was synthesized and labeled with (125)Iodine using chloramine-T. Mass spectroscopy revealed that chloramine-T-treatment did not oxidize YQLS. (125)I-YQLS bound with high affinity to cells expressing the murine CRF receptor 1 (CRFR1), CRF receptor 2 (CRFR2), and the mouse brain regions known to express both CRF receptors. (125)I-YQLS chemically cross-linked to CRFR1. In conclusion, (125)I-YQLS is oxidation-resistant, high affinity radioligand that can be chemically cross-linked to the CRF receptors.

Amino Acid Sequence↗
PubMed2001

Hypochlorous acid damages erythrocyte membrane proteins and alters lipid bilayer structure and fluidity.

Treatment of human erythrocyte membranes with active forms of chlorine (hypochlorous acid and chloramine T) resulted in a concentration-dependent inhibition of the membrane Na(+), K(+)- and Mg(2+)-ATPases. Membrane protein thiol group oxidation was consistent with inactivation of enzymes and preceded oxidation of tryptophan residues and chloramine formation. Erythrocyte exposure to hypochlorous acid led to complex changes of cell membrane rigidity and cell morphological transformations: cell swelling, echinocyte formation, and haemolysis. The inhibition of ion pump ATPases of human erythrocyte membranes may be due to direct oxidation of essential residues of enzyme (thiol groups) and structural rearrangement of the membrane.

Adenosine Triphosphatases↗
PubMed1982

Comparison of surface iodination methods by electron microscopic autoradiography applied in vitro to different life-stages of Dipetalonema viteae (Filarioidea).

Different states of Dipetalonema viteae (males, females, microfilariae, and 3rd-stage larvae) have been iodinated in vitro under physiological conditions by chloroglycoluril, lactoperoxidase or chloramine T. The concentrations of the catalysts were correlated with the viability of the worms. Localization of the label with the different iodination methods had been visualized by electro microscopical autoradiography. Chloroglycoluril-mediated iodination is predominantly localized on the filarial cuticle. Lactoperoxidase-catalysed iodination is less specific and chloramine T catalyses iodination in a gradient decreasing from the cuticle to inner structures. It is necessary to visualize the labelling by electron microscopical autoradiography prior to biochemical and immunological experiments to avoid the extraction of structures iodinated by leakage of the catalyst into sub-cuticular regions.

Animals↗
PubMed2001

Hypochlorous acid produced by the myeloperoxidase system of human phagocytes induces covalent cross-links between DNA and protein.

Phagocytic oxidants have been implicated in tissue injury and oncogenesis, and their pathophysiological role in modifying nucleobases and amino acids has been widely explored. Their ability to cross-link proteins and DNA, however, has not been considered, even though reversible DNA-protein interactions are key to gene expression and to DNA replication and repair. In the current studies, we show that hypochlorous acid (HOCl), generated by the myeloperoxidase-hydrogen peroxide-chloride system of phagocytes, cross-links single-stranded DNA-binding protein (SSB) to single-stranded oligonucleotides. Exposure of SSB and a homopolymer of radiolabeled thymidine (dT(40)) to HOCl resulted in the formation of a radiolabeled band with slower mobility than the free oligonucleotide, as determined by denaturing polyacrylamide gel electrophoresis. This radiolabeled band did not appear if the reaction mixture was treated with protease or nuclease, indicating that it represents a covalent complex of DNA and protein. Oligonucleotides of adenosine and cytidine behaved similarly to the thymidine oligonucleotide, demonstrating that they are also capable of participating in the cross-linking reaction. The covalent complex of radiolabeled dT(40) and SSB was also generated by chloramines and the complete myeloperoxidase-hydrogen peroxide-chloride system. The enzymatic reaction required each component of the system and was inhibited by heme poisons and chloride-free conditions, implicating myeloperoxidase and HOCl. DNA-protein cross-links were generated in Escherichia coli exposed to HOCl, suggesting that double-stranded DNA is also a target for the reaction. These results indicate that long-lived chloramines and HOCl generated by myeloperoxidase can generate covalent DNA-protein cross-links that may contribute to the mutagenic and cytotoxic effects of phagocytes on microbial pathogens and host tissue.

Chloramines↗
PubMed1975

Selective oxidation of methionine residues in proteins.

Methionine residues in peptides and proteins were oxidized to methionine sulfoxides by mild oxidizing reagents such as chloramine-T and N-chlorosuccinimide at neutral and slightly alkaline pH. With chloramine-T cysteine was also oxidized to cystine but no other amino acid was modified; with N-chlorosuccinimide tryptophans were oxidized as well. In peptides and denaturated proteins all methionine residues were quantitatively oxidized, while in native proteins only exposed methionine residues could be modified. Extent of oxidation of methionine residues was determined by quantitative modification of the unoxidized methionine residues with cyanogen bromide (while methionine sulfoxide residues remained intact), followed by acid hydrolysis and amino acid analysis. Methionine was determined as homoserine and methionine sulfoxide was reduced back to methionine. Sites of oxidation were identified in a similar way by cleaving the unoxidized methionyl peptide bonds with cyanogen bromide, followed by quantitative end-group analysis of the new amino-terminal amino acids (by an automatic sequencer).

Amino Acid Sequence↗
PubMed2004

Investigations of the reactions of monochloramine and dichloramine with selected phenols: examination of humic acid models and water contaminants.

Our paper reports on the reactivities and orientations of two common phenols, phenol (2) and m-cresol (3), and some of their chlorinated intermediates with aqueous monochloramine, NH2Cl, and dichloramine, NHCl2. We also examined the further reactivity of 2,4,6-trichlorophenol (4) with the chloramines. The phenols are an important area of investigation because they are substituents in the humic acids and are common contaminants in water. m-Cresol (3) was found to be more reactive than phenol (2)with both chlorinating agents. Both NH2Cl and NHCl2were sufficiently reactive to chlorinate all positions ortho and para to the hydroxyl groups. Mono- and dichloramine showed the same orientation with 2 but different orientations in their reactions with the substituent phenols. Indophenol (as its salt) was formed to a minor extent at high pH but not at pH 9. Both NH2Cl and NHCl2 rapidly replaced the parachlorine in 2,4,6-trichlorophenol (4) to give a mixture of 2,6-dichloro-1,4-benzoquinone-4-(N-chloro) imine (5) and 2,6-dichloro-1,4-benzoquinone (18). Similar reactions occurwith 2,4,6-trichloro-m-cresol (17) and 2,4,6-trichloro-3-methoxyphenol (29). The products for 17 were confirmed by mass spectrometry (El and Cl), 1H NMR, 13C NMR, and IR; the products for 29 were confirmed by mass spectrometry (El and Cl) and IR. An ion radical mechanism is suggested to account for the chlorine replacement by the chloramines. [No side chain oxidation of the methyl group in 17 in H20 or ether occurred, with or without ultraviolet radiation.] Both 5 and 18 underwent further chlorination with NH2Cl or NHCl2. Imine 5 did not function as a chlorinated agent.

Chloramines↗
PubMed2004

Chemical and biological characterization of newly discovered iodoacid drinking water disinfection byproducts.

Iodoacid drinking water disinfection byproducts (DBPs) were recently uncovered in drinking water samples from source water with a high bromide/iodide concentration that was disinfected with chloramines. The purpose of this paper is to report the analytical chemical identification of iodoacetic acid (IA) and other iodoacids in drinking water samples, to address the cytotoxicity and genotoxicity of IA in Salmonella typhimurium and mammalian cells, and to report a structure-function analysis of IA with its chlorinated and brominated monohalogenated analogues. The iodoacid DBPs were identified as iodoacetic acid, bromoiodoacetic acid, (Z)- and (E)-3-bromo-3-iodopropenoic acid, and (E)-2-iodo-3-methylbutenedioic acid. IA represents a new class (iodoacid DBPs) of highly toxic drinking water contaminants. The cytotoxicity of IA in S. typhimurium was 2.9x and 53.5x higher than bromoacetic acid (BA) and chloroacetic acid (CA), respectively. A similar trend was found with cytotoxicity in Chinese hamster ovary (CHO) cells; IA was 3.2x and 287.5x more potent than BA and CA, respectively. This rank order was also expressed in its genotoxicity with IA being 2.6x and 523.3x more mutagenic in S. typhimurium strain TA100 than BA and CA, respectively. IA was 2.0x more genotoxic than BA and 47.2x more genotoxic than CA in CHO cells. The rank order of the toxicity of these monohalogenated acetic acids is correlated with the electrophilic reactivity of the DBPs. IA is the most toxic and genotoxic DBP in mammalian cells reported in the literature. These data suggest that chloraminated drinking waters that have high bromide and iodide source waters may contain these iodoacids and most likely other iodo-DBPs. Ultimately, it will be important to know the levels at which these iodoacids occur in drinking water in order to assess the potential for adverse environmental and human health risks.

Acetates↗
PubMed2005

Interactions of fluoroquinolone antibacterial agents with aqueous chlorine: reaction kinetics, mechanisms, and transformation pathways.

Kinetics, products, and mechanistic aspects of reactions between free available chlorine (HOCl/OCl-), ciprofloxacin (CF), and enrofloxacin (EF) were extensively investigated to elucidate the behavior of fluoroquinolone antibacterial agents during water chlorination processes. Although the molecular structures of these two substrates differ only with respect to degree of N(4) amine alkylation, CF and EF exhibit markedly different HOCl reaction kinetics and transformation pathways. HOCI reacts very rapidly at CF's secondary N(4) amine, forming a chloramine intermediate that spontaneously decays in aqueous solution by concerted piperazine fragmentation. In contrast, HOCl reacts relatively slowly at EF's tertiary N(4) amine, apparently forming a highly reactive chlorammonium intermediate (R3N-(4)Cl+) that can catalytically halogenate EF or other substrates present in solution. Flumequine, a fluoroquinolone that lacks the characteristic piperazine ring, exhibits no apparent reactivity toward HOCI but appears to undergo facile halodecarboxylation in the presence of R3N(4)-Cl+ species derived from EF. Measured reaction kinetics were validated in real water matrixes by modeling CF and EF losses in the presence of free chlorine residuals. Combined chlorine (CC) kinetics were determined under selected conditions to evaluate the potential significance of reactions with chloramines. CF's rapid kinetics in direct reactions with HOCl, and relatively high reactivity toward CC, indicate that secondary amine-containing fluoroquinolones should be readily transformed during chlorination of real waters, whether applied chlorine doses are present as free or combined residuals. However, EF's slower HOCl reaction kinetics, recalcitrance toward CC, and participation in the catalytic halogenation cycle described herein suggest that tertiary amine-containing fluoroquinolones will be comparatively stable during most full-scale water chlorination processes.

Amines↗
PubMed1999

Tert-butylsulfonamide. A new nitrogen source for catalytic aminohydroxylation and aziridination of olefins.

[reaction: see text] The N-chloramine salt of tert-butylsulfonamide has been shown to be an efficient nitrogen source and the terminal oxidant for catalytic aminohydroxylation and aziridination of olefins, resembling closely Chloramine-T by its behavior in these catalytic reactions. The sulfonyl-nitrogen bond in the product or its derivatives is easily cleaved under mild acidic conditions, allowing for facile liberation of the amino group.

Alkenes↗
PubMed2002

Antithrombotic activity of N,N-dichlorotaurine on mouse model of thrombosis in vivo.

Intravenous injection of chloramine derivatives of amino acids and taurine reduced the mortality rate in mice with thrombosis induced by intravenous injection of ADP or collagen-epinephrine mixture. Intravenous injection of N,N-dichlorotaurine caused 50% inhibition of platelet aggregation induced by ADP and measured in the platelet-enriched plasma in vitro. The antithrombotic effect of chloramine derivatives of amino acids and taurine is related to their ability to suppress functional activity of platelets.

Adenosine Diphosphate↗
PubMed1967

A study of some factors that influence the iodination of ox insulin.

1. The influence of carrier iodide, iodine monochloride and pH on the labelling of ox insulin with (131)I by the iodine monochloride method have been studied. 2. The quantitative effect of the iodide in the radioactive iodine preparation was that predicted from a calculation of its specific activity. No other interfering factors were detected in the [(131)I]iodide solutions used. 3. Increasing the molar ratio of iodine monochloride to insulin resulted in an increase followed progressively by a decrease in the proportion of (131)I bound, while the total iodine bound increased to an amount characteristic of pH and thereafter remained constant. 4. The influence of pH on the iodination of insulin with iodine monochloride was complex and the pH curve showed two maxima, at pH2.8 and 6.4. At pH2.8 it was not possible to exceed 8 atoms of iodine bound per molecule by increasing the molar ratio of iodine monochloride. Similarly, at pH6.4 the substitution value of 11.5 atoms of iodine per molecule could not be exceeded. 5. Iodinated insulins containing an average of 1.96, 2.74, 6.0 and 7.0 atoms of iodine per molecule fully retained the ability to bind guinea-pig anti-(ox insulin) serum, and the ability to compete with unlabelled insulin for antibody sites only became significantly changed in the most highly substituted preparations and in the presence of large concentrations of unlabelled insulin. 6. The method for the iodination of insulin with 98% incorporation of (131)I by using chloramine-t is described. 7. (131)I-iodinated insulin prepared with graded quantities of chloramine-t in excess of that required for efficient labelling was less efficiently bound by guinea-pig anti-(ox insulin) serum than insulin labelled by the iodine monochloride method.

Animals↗
PubMed1973

Binding of parathyroid hormone to bovine kidney-cortex plasma membranes.

1. Plasma membranes were purified from bovine kidney cortex, with a fourfold increase in specific activity of parathyroid hormone-sensitive adenylate cyclase over that in the crude homogenate. The membranes were characterized by enzyme studies. 2. Parathyroid hormone was labelled with (125)I by an enzymic method and the labelled hormone shown to bind to the plasma membranes and to be specifically displaced by unlabelled hormone. Parathyroid hormone labelled by the chloramine-t procedure showed no specific binding. (75)Se-labelled human parathyroid hormone, prepared in cell culture, also bound to the membranes. 3. Parathyroid hormone was shown to retain biological activity after iodination by the enzymic method, but no detectable activity remained after chloramine-t treatment. 4. High concentration of pig insulin inhibited binding of labelled parathyroid hormone to plasma membranes and partially inhibited the hormone-sensitive adenylate cyclase activity in a crude kidney-cortex preparation. 5. EDTA enhanced and Ca(2+) inhibited binding of labelled parathyroid hormone to plasma membranes. 6. Whereas rat kidney homogenates were capable of degrading labelled parathyroid hormone to trichloroacetic acid-soluble fragments, neither crude homogenates nor purified membranes from bovine kidney showed this property. 7. Binding of parathyroid hormone is discussed in relation to metabolism and initial events in hormone action.

Adenylyl Cyclases↗
PubMed2005

Oxidation of heparan sulphate by hypochlorite: role of N-chloro derivatives and dichloramine-dependent fragmentation.

Activated phagocytes release the haem enzyme MPO (myeloperoxidase) and produce superoxide radicals and H2O2 via an oxidative burst. MPO uses H2O2 and Cl- to form HOCl, the physiological mixture of hypochlorous acid and its anion present at pH 7.4. As MPO binds to glycosaminoglycans, oxidation of extracellular matrix and cell surfaces by HOCl may be localized to these materials. However, the reactions of HOCl with glycosaminoglycans are poorly characterized. The GlcNAc (N-acetylglucosamine), GlcNSO3 (glucosamine-N-sulphate) and GlcNH2 [(N-unsubstituted) glucosamine] residues of heparan sulphate are potential targets for HOCl. It is shown here that HOCl reacts with each of these residues to generate N-chloro derivatives, and the absolute rate constants for these reactions have been determined. Reaction at GlcNH2 residues yields chloramines and, subsequently, dichloramines with markedly slower rates, k2 approximately 3.1x10(5) and 9 M(-1) x s(-1) (at 37 degrees C) respectively. Reaction at GlcNSO3 and GlcNAc residues yields N-chlorosulphonamides and chloramides with k2 approximately 0.05 and 0.01 M(-1) x s(-1) (at 37 degrees C) respectively. The corresponding monosaccharides display a similar pattern of reactivity. Decay of the polymer-derived chloramines, N-chlorosulphonamides and chloramides is slow at 37 degrees C and does not result in major structural changes. In contrast, dichloramine decay is rapid at 37 degrees C and results in fragmentation of the polymer backbone. Computational modelling of the reaction of HOCl with heparan sulphate proteoglycans (glypican-1 and perlecan) predicts that the GlcNH2 residues of heparan sulphate are major sites of attack. These results suggest that HOCl may be an important mediator of damage to glycosaminoglycans and proteoglycans at inflammatory foci.

Animals↗
PubMed1998

Hypochlorite-induced damage to proteins: formation of nitrogen-centred radicals from lysine residues and their role in protein fragmentation.

Stimulated monocytes and neutrophils generate hypochlorite (HOCl) via the release of the enzyme myeloperoxidase and hydrogen peroxide. HOCl damages proteins by reaction with amino acid side-chains or backbone cleavage. Little information is available about the mechanisms and intermediates involved in these reactions. EPR spin trapping has been employed to identify radicals on proteins, peptides and amino acids after treatment with HOCl. Reaction with HOCl gives both high- and low-molecular-mass nitrogen-centred, protein-derived radicals; the yield of the latter increases with both higher HOCl:protein ratios and enzymic digestion. These radicals, which arise from lysine side-chain amino groups, react with ascorbate, glutathione and Trolox. Reaction of HOCl-treated proteins with excess methionine eliminates radical formation, which is consistent with lysine-derived chloramines (via homolysis of N-Cl bonds) being the radical source. Incubation of HOCl-treated proteins, after removal of excess oxidant, gives rise to both nitrogen-centred radicals, over a period of hours, and time-dependent fragmentation of the protein. Treatment with excess methionine or antioxidants (Trolox, ascorbate, glutathione) protects against fragmentation; urate and bilirubin do not. Chloramine formation and nitrogen-centred radicals are therefore key species in HOCl-induced protein fragmentation.

Amino Acids↗
PubMed2004

Acute columnaris infection in channel catfish, Ictalurus punctatus (Rafinesque): efficacy of practical treatments for warmwater aquaculture ponds.

Columnaris disease was induced in channel catfish, Ictalurus punctatus (Rafinesque), by bath exposure to four highly virulent isolates of Flavobacterium columnare. In untreated controls, mortality began 20 h after exposure and reached 100% by 48 h. Mortality in channel catfish given antibiotic treatments with oxytetracycline or a combination of sulphadimethoxine and ormetoprim in feed prior to bacterial challenge was zero with all four strains of F. columnare. Diquat (Zeneca Agricultural Products, Wilmington, DE, USA) was the most effective bath treatment; mortality with all four strains was zero. With potassium permanganate, chloramine-T, hydrogen peroxide and copper sulphate, bath treatment efficacy varied significantly among strains (P = 0.0346) and among treatments (P = 0.0033). Bath treatments with chloramine-T and potassium permanganate significantly reduced (P < 0.05) mortality from 100 to 75 and 69%, respectively, but copper sulphate and hydrogen peroxide treatments were not effective. Based on our results, oral antibiotics prevented columnaris disease but, of the bath treatments, only Diquat produced a dramatic reduction in the mortality of acutely infected fish. Diquat is labelled for aquatic use as an herbicide in the USA but in large ponds it is prohibitively expensive.

Animals↗
PubMed2003

Antimicrobial activity of a new intact skin antisepsis formulation.

UNLABELLED: Different antiseptic formulations have shown limitations when applied to disinfecting intact skin, notably short-term tolerability and/or efficacy. The purpose of this study was optimizing a new antiseptic formulation specifically targeted at intact skin disinfection and evaluating its in vitro microbicidal activity and in vivo efficacy. METHODS: The biocidal properties of the antiseptic solution containing 0.5% chloramine-T diluted in 50% isopropyl alcohol (Cloral; Eurospital SpA Trieste, Italy) were measured in vitro versus gram-positive-, gram-negative-, and acid-alcohol-resistant germs and fungi with standard suspension tests in the presence of fetal bovine serum. Virus-inhibiting activity was evaluated in vitro against human cytomegalovirus, herpes simplex virus, poliovirus, hepatitis B virus, and hepatitis C virus. Tests used different methods for the different biologic and in vitro replication capacity of these human viruses. Lastly, Cloral tolerability and skin colonization retardation efficacy after disinfection were studied in vivo. RESULTS: The antiseptic under review showed fast and sustained antimicrobial activity. The efficacy of Cloral against clinically important bacterial and viral pathogens and fungi was highlighted under the experimental conditions described in this article. Finally, microbial regrowth lag and no side effects were documented in vivo after disinfection of 11 volunteers. CONCLUSIONS: A stable chloramine-T solution in isopropyl alcohol may be suggested for intact skin antisepsis.

2-Propanol↗
PubMed2005

Differential effects of cysteine and methionine residues in the antioxidant activity of human serum albumin.

Antioxidant properties of human serum albumin (HSA) may explain part of its beneficial role in various diseases related to free radical attack. In the present study, the antioxidant role of Cys and Met was studied by copper-mediated oxidation of human low density lipoproteins and by free radical-induced blood hemolysis which essentially assessed metal-chelating and free radical scavenging activities, respectively. Mild conditions were set up to specifically modify Cys and Met residues by N-ethylmaleimide (NEM) and chloramine T treatments, respectively. We found that Met and Cys accounted for 40-80% of total antioxidant activity of HSA. Copper binding to HSA was decreased by about 50% with chloramine T treatment of Met whereas no change was observed after NEM treatment of Cys. Although other amino acid residues are likely to be involved in anti-/prooxidant properties of HSA, from our data, we propose that Cys chiefly works as a free radical scavenger whereas Met mainly acts as a metal chelator.

Antioxidants↗
PubMed1999

Neopterin derivatives modulate toxicity of reactive species on Escherichia coli.

Neopterin and 7,8-dihydroneopterin are released by human monocytes/macrophages upon stimulation with interferon-gamma. In parallel, a panel of highly reactive species is produced by macrophages as part of their cytotoxic armature, which is directed against microbial and viral challenge and against malignant growth. Recently, neopterin and 7,8-dihydroneopterin were shown to modulate the action of reactive species in vitro. In this study we investigated the impact of neopterin and 7,8-dihydroneopterin on the toxicity of reactive species, namely chloramine-T, H2O2, hypochlorite, nitrite, and formaldehyde, respectively. We studied the growth inhibition of Escherichia Coli (E. coli) by these toxic agents and its modulation by neopterin and 7,8-dihydroneopterin. Bacterial growth was monitored by optical density of suspension cultures at 600 nm. Compared to control experiments, neopterin enhanced toxicity of all reactive species tested except formaldehyde, while 7,8-dihydroneopterin reduced activity of hypochlorite and chloramine-T. No significant impact of the pteridines could be established for H2O2-mediated and formaldehyde-mediated growth inhibition. The data support the concept that neopterin and 7,8-dihydroneopterin produced during immune response in humans could be important to modulate the action of reactive species released in parallel.

Anti-Bacterial Agents↗