Trichloromethyl Radical Research Articles

Heme peptide as a model substance for halogenomethane activation and heme modification

Octa-heme peptide (CHP) obtained from Candida krusei cytochrome c was tested for suicidal activation of halogenomethanes. Under anerobic conditions, CHP was kept in the reduced state in the presence of NADPH and NADPH-cytochrome P-450 reductase. Addition of CBrCl 3 to the reduced CHP caused spectral changes such as rapid disappearance of α and β bands and gradual decrease in the γ-peak height, accompanied by oxidation of NADPH. Heme content of the reaction mixture, determined as pyridine hemochrome, also decreased NADPH dependently. CCl 4 was less effective than CBrCl 3, while CHCl 3 had almost no effect. N-tert-butyl-α-phenylnitrone (PBN) suppressed the CBrCl 3-induced heme damage, and resulted in the formation of radical adduct ·PBN-CCl 3 as evidenced by ESR spectroscopy. Radical formation was also observed with CCl 4. The CHP damage induced by CBrCl 4 was also accompanied by the release of Br − about 11–12-times molar excess of CHP, whereas the release of CHCl 3 was about 20% that of Br −. FD-MS assay of the product of CHP reaction suggested that 10 trichloromethyl radicals bonded with CHP. Thus, CBrCl 3 undergoes single-electron reduction in the presence of reduced CHP to trichloromethyl radicals, which covalently bind to CHP molecules. Heme peptide may be a useful tool in the study of mechanisms involved in the destruction of cytochrome P-450 by halogenomethanes.

Kinetics of the reaction trichloromethyl + bromine and thermochemistry of trichloromethyl radical and cation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTKinetics of the reaction trichloromethyl + bromine and thermochemistry of trichloromethyl radical and cationJeffrey W. Hudgens, Russell D. Johnson III, R. S. Timonen, J. A. Seetula, and D. GutmanCite this: J. Phys. Chem. 1991, 95, 11, 4400–4405Publication Date (Print):May 1, 1991Publication History Published online1 May 2002Published inissue 1 May 1991https://doi.org/10.1021/j100164a043RIGHTS & PERMISSIONSArticle Views129Altmetric-Citations55LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (667 KB) Get e-Alerts

Interaction of trichloromethyl radicals with phenylalanine

Chemically or enzymatically generated trichloromethyl free radicals interact with liposoluble derivatives of phenylalanine. In vitro, in a chemical system to produce .CCl3 (benzoyl peroxide catalysis), this radical attacked N-acetyl-d,l-phenylalanine methyl ester (PheMeAc) to give a monochlorinated derivative (I) and an unsaturated imine type derivative of PheMeAc (II). Using a liver microsomal system to produce .CCl3 (microsomes + NADPH + CCl4 under nitrogen), the attack of PheMeAc did not result in I or II formation, but in production of benzene. The phenylalanine content in liver microsomal proteins from rats treated with CCl4 6 h before, was not significantly decreased. The results suggest that phenylalanine is a potential target of .CCl3.

Production and photodissociation of trichloromethyl radicals in a molecular beam

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTProduction and photodissociation of trichloromethyl radicals in a molecular beamEric J. Hintsa, Xinsheng Zhao, William M. Jackson, Walter B. Miller, Alec M. Wodtke, and Yuan T. LeeCite this: J. Phys. Chem. 1991, 95, 7, 2799–2802Publication Date (Print):April 1, 1991Publication History Published online1 May 2002Published inissue 1 April 1991https://doi.org/10.1021/j100160a031RIGHTS & PERMISSIONSArticle Views110Altmetric-Citations18LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (550 KB) Get e-Alerts

Protective effect of chromium(III) on acute lethal toxicity of carbon tetrachloride in rats and mice

Trivalent chromium (Cr(III)) preadministered intraperitoneally (5 mg Cr/kg body weight) to rats and mice protected these animals from acute lethal toxicity of carbon tetrachloride (CCl 4). Some other metals, Cr(VI), Cu(II), and Zn(II), had no effect on CCl 4 lethal toxicity. DL-α-tocopherol, one of the antioxidative agents, showed similar protective effects to Cr(III). Activities of serum GOT and GPT in mice were increased sharply by the administration of CCl 4, but these elevations were depressed by Cr(III) preadministration. Serum glucose levels of mice increased transiently after CCl 4 administration and then in the control group fell to hypoglycemic levels after 6 hr, whereas the Cr(III)-pretreated group kept to homeostatic levels. Lipid peroxidation of microsomes in mice 24 hr after Cr(III) administration was lower than that of the control. These results suggest that Cr(III) preadministered to mice might act as a radical scavenger to CCl 4 to form trichloromethyl radicals which are a major initial product of CCl 4 in liver cells.

ZnTPP-sensitized photoreaction of α-methylstyrene in the presence of Et 3N and CCl 4

The photolysis (greater than 400 nm) of α-methylstyrene ( 1), sensitized by zinc 5,10,15,20-tetraphenylporphine (ZnTPP) in the presence of Et 3N and CCl 4, was studied. The main products were the two stereoisomers of 3,4-dimethyl-3,4-diphenyl-1,1,1,6,6,6-hexachlorohexane ( 2 and 3), which probably resulted from the addition of a trichloromethyl radical to 1, followed by radical coupling. Yields of approximately 11 000% were obtained on the basis of ZnTPP. 2-Phenyl-4,4,4-trichloro-1-butene ( 4), one of the previously reported main products from the reaction of 1 and CCl 3 was only obtained in very low yields. In addition to the trichloromethylation of 1, chloroform was produced in very high yields (up to 130 000% on the basis of ZnTPP).

Detection of spin adducts in blood after administration of carbon tetrachloride to rats

Rats were treated with CCl 4 and the spin trapping agent α-phenyl- N-t-butyl nitrone (PBN), followed by ESR investigations on samples of heparinized blood. The major signal detected was the ascorbate semidione radical, but smaller concentrations of the carbon dioxide radical anion spin adduct of PBN could also be detected. The ESR signals were more intense when experiments were conducted with plasma, rather than blood. The spin adducts detected were not associated with the red blood cells, and their apparent concentrations increased when the cells were removed by centrifugation. The addition of ascorbate oxidase to the samples markedly diminished the intensity of the ascorbate semidione radical. When plasma samples from CCl 4-treated rats were extracted into toluene, the ESR spectrum of the trichloromethyl adduct of PBN was observed in the extract. Because the spectrum of this adduct was not observed in direct ESR studies of plasma, it is possible that immobilization occurred in the presence of plasma proteins. Evidence to support this hypothesis was developed by adding bovine serum albumin (BSA) to an aqueous solution of the trichloromethyl radical adduct of PBN. As the BSA concentration was increased, the intensity of the ESR spectrum was markedly diminished, and displayed features of an immobilized adduct.

Experimental and ab initio studies of electronic structures of the trichloromethyl radical and cation

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTExperimental and ab initio studies of electronic structures of the trichloromethyl radical and cationJeffrey W. Hudgens, Russell D. Johnson III, Bilin P. Tsai, and Sherif A. KafafiCite this: J. Am. Chem. Soc. 1990, 112, 15, 5763–5772Publication Date (Print):July 1, 1990Publication History Published online1 May 2002Published inissue 1 July 1990https://doi.org/10.1021/ja00171a015RIGHTS & PERMISSIONSArticle Views107Altmetric-Citations41LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (1 MB) Get e-Alerts Get e-Alerts

Metabolism-based covalent bonding of the heme prosthetic group to its apoprotein during the reductive debromination of BrCCl3 by myoglobin.

The reductive metabolism of BrCCl3 by ferrous myoglobin leads to the alteration of the prosthetic heme to form products that can be dissociated from the protein and to those that are irreversibly bound to the protein. The major dissociable or soluble heme metabolites have recently been characterized. In this study, the irreversibly bound heme product was characterized by Edman degradation, amino acid analysis, and electronic absorption and mass spectrometry of peptides derived from the altered protein. It was found that the prosthetic heme was modified by a CCl2 moiety derived from BrCCl3 and was covalently bound to histidine residue 93, the normal proximal ligand to the heme-iron. The data are consistent with a mechanism by which the trichloromethyl radical reacts with the heme to form an intermediate that either can alkylate the proximal histidine residue or form soluble metabolites. The covalent bonding of the heme prosthetic moiety to the apoprotein likely leads to a change in the tertiary structure of the protein that may be responsible for its altered catalytic activity as well as its enhanced susceptibility to proteolysis. Similar processes may account, at least in part, for the covalent alteration of the heme prosthetic group of other hemoproteins caused by xenobiotics and endogenous substrates.

Ab initio calculation of the inversion barrier in the trichloromethyl radical

The inversion barrier in the CCl 3 radical has been calculated by means of the UHF and UMP2 models in conjunction with basis sets of split-valence (6–31G), polarized split-valence (6–31G *), double-zeta plus polarization or triple-zeta plus double polarization quality. For this low-barrier system, the UMP2 correlation corrections appeared to be important in calculating the barrier height. At the UMP2/6–31G, UMP2/6–31G * and UMP2/DZP levels, electron correlation was found to increase the CCl 3 barrier, in contrast to the case of the CF 3 radical as described recently by Curtiss and Pople.

Biochemical mechanism of metallothionein-carbon tetrachloride interaction in vitro

To elucidate the mechanism underlying the protective effect of metallothionein (MT) against carbon tetrachloride (CCl 4) toxicity, in vitro experiments were carried out to study the interaction of metallothionein and CCl 4. Results from this study showed that incubation of Cd,Zn-MT with (CCl 4)in the presence of hepatic microsomes and NADPH resulted in a time-dependent depletion of MT thiols with a concurrent reduction in the metal-binding sites of the protein. Moreover, this reaction also released Zn and Cd from MT. Results from experiments conducted to determine whether or not the CCl 4-induced decrease in MT-thiol content was due to the scavenging of (CCl 4)metabolite(s) showed that the trichloromethyl radical, chloroform and phosgene as well as the products of (CCl 4)-induced microsomal lipid peroxidation were not directly involved. Although covalent binding of 14(CCl 4)to MT was detected following incubation in the presence of a microsomal bioactivation system, it did not account for the CCl 4-induced loss of MT thiol groups for the following reasons: (i) prior oxidation of sulfhydryl groups of MT by hydrogen peroxide did not alter the binding; and (ii) anaerobiosis did not alter the extent of covalent binding but obliterated the inhibitory effect of (CCl 4)on MT thiol content. Measurement of the thiol content of CCl 4-treated MT after treatment with 1,4-dithiothreitol revealed that all the thiol groups that were lost subsequent to CCl 4treatment could be regenerated. These data suggest that CCl 4-linked oxidation of MT, rather than the covalent binding of 14CCl 4metabolite(s), may be responsible for the CCl 4-induced loss of metal binding sites of MT with the concurrent release of Zn and Cd. However, the precise role of the metal released during the oxidation of MT in CCl 4 toxicity remains to be defined.

Photoinduced electron transfer from dialkyl nitroxides to halogenated solvents

Laser flash photolysis (LFP) at wavelengths within the charge-transfer absorption present in CCl{sub 4} solutions of 2,2,6,6-tetramethylpiperidine-N-oxyl (TEMPO) yields the oxoammonium chloride of TEMPO, 1 ({lambda}{sub max} = 460 nm), and the trichloromethyl radical in an essentially instantaneous ({le}18 ps) process. The primary photochemical event is an electron transfer from TEMPO to CCl{sub 4}, and this is followed by immediate decomposition of the CCl{sub 4}{sup {sm bullet}{minus}} radical anion to Cl{sup {minus}} and Cl{sub 3}C{sup {sm bullet}}. An independent synthesis of 1 confirmed that the absorption attributed to this species has been correctly assigned. The formation of Cl{sub 3}C{sup {sm bullet}} was inferred by its trapping by molecular oxygen. LFP of TEMPO in other halogenated solvents and of other nitroxides in halogenated solvents has confirmed the generality of these photoreactions.

Reactivity of substituted styrenes in the catalytic addition reaction with the trichloromethyl radical

Relative reactivities have been investigated in the catalytic addition of tetrachloromethane to substituted styrenes by the competitive method. The polar effects of substituents on benzene ring were correlated with Hammett equation for a copper and ruthenium catalyst, giving ρ values equal to -0.39 and -0.18 respectively. The results indicate that in contrast to classical additions the catalytic addition of tetrachloromethane is not a free radical chain process but that the trichloromethyl radical, presumably coordinated, reacts with the carbon-carbon double bond via innersphere pathways.

Direct Observation of Spin-Trapped Carbon Dioxide Radicals in Hepatocytes Exposed to Carbon Tetrachloride

Carbon dioxide radical adducts of the spin trapping agent, alpha-phenyl N-t-butyl nitrone (PBN), have been observed to occur in the urine and bile of rats exposed to carbon tetrachloride as well as in perfusates of liver in which the perfusion medium contained carbon tetrachloride (Connor et al., J. Biol. Chem., 261, 4542, (1986]. The carbon dioxide adduct was proven to be derived from CCl4 by use of 13-C-labelled compound. These adducts were not observed in the liver itself suggesting that they might be rapidly secreted from the liver. However, using isolated hepatocytes, we have demonstrated that the carbon dioxide radical adduct can be observed directly in the liver cells as it is formed. Since this water-soluble adduct cannot be extracted by non-aqueous solvents such as chloroform or toluene, its formation in liver in vivo or in perfused livers was not detected. Lowering the oxygen tension in the system diminished the intensity of production of the carbon dioxide adduct, consistent with the adduct being produced as a result of .OOCCl3 generation. It is not clear the extent to which this adduct is formed as a result of the .CO2 radical or is produced by metabolic oxidation of the trichloromethyl radical adduct of PBN per se to the carbon dioxide radical adduct. The intensity of the signal of the carbon dioxide radical adduct suggests that adduct conversion may be the route of formation since it seems unlikely that a sufficient amount of the halocarbon could be metabolized to .COCl or .CO2 radicals to generate a signal of the magnitude involved.(ABSTRACT TRUNCATED AT 250 WORDS)

Mass Spectroscopy and Chromatography of the Trichloromethyl Radical Adduct of PhenylTer T-Butyl Nitrone

Positive structural identification of the PBN-trichloromethyl spin adduct in vitro was accomplished with the use of high pressure liquid chromatography and/or gas chromatography coupled with mass spectrometry. Both thin layer and liquid chromatography were used to separate a complex mixture of compounds from rat liver extracts treated with CCl4 in vitro and in vivo. Deuterated PBN's (PBN-d9; tert-butyl deuteration, or PBN-d14; both phenyl and tert-butyl deuteration) were also used to aid in the mass spectral analysis of spin adducts from liver extracts of CCl4 exposed rat livers, since the tert-butyl group fragment ion. C4D9+ (m/z = 66) is always present for PBN and PBN spin adducts. In addition, the masses of the ion peaks increase by the amount of deuteration, i.e. an increase of 9 for PBN-d9 or PBN-d14 in comparison to normally synthesized PBN.

Promethazine inhibits the formation of aldehydic products of lipid peroxidation but not covalent binding resulting from the exposure of rat liver fractions to CCl4.

Promethazine is known to have protective activity in relation to CCl4-induced liver necrosis. This hepatoprotective property has been investigated with regard to the free radical scavenging and antioxidant properties of promethazine using isolated hepatocytes and microsomal suspensions. CCl4 is activated in both systems to free radical metabolites that bind covalently to lipid and protein, and initiate lipid peroxidation. A large number of carbonyl products is produced during CCl4-induced lipid peroxidation; promethazine strongly inhibits the production of all classes of carbonyl compounds in both microsomal suspensions and isolated hepatocytes. In contrast, promethazine is a very weak inhibitor of the covalent binding of metabolites of CCl4. We conclude that promethazine acts by scavenging the trichloromethylperoxyl radical and lipid peroxyl radicals, and is a weak scavenger of the trichloromethyl radical. These data, when considered together with the hepatoprotective effects of promethazine, suggest that lipid peroxidation is of relatively more importance than covalent binding in the pathogenesis of CCl4-induced liver necrosis.

Dimethyldisulfide formation during trichloromethyl radical attack on methionine

Etude de la structure des composes volatils formes quand le radical libre trichloromethyl chimiquement produit interagit avec la methionine. Trichloromethyl produit enzymatiquement mis en presence de methionine ou d'ester ethylique de methionine genere aussi du dimethyl dimethyl (disulfure)

The photochemical behaviour of 3-( N, N-dimethylamino)-2 H-1-benzopyran-2-one in tetrachloromethane: the influence of chloromethanes on quenching of fluorescence

3-( N, N-dimethylamino)-2 H-benzopyran-2-one (DMAC) sensitizes the decomposition of CCl 4 during the photolysis in the near UV region (λ > 290 nm). The products of the photolysis are 3-( N-methylamino)-2 H-1-benzopyran-2-one (MAC) as a result of the demethylation of DMAC and the compounds formed by the reaction of DMAC with the trichloromethyl radical 3-( N, N-dimethylamino)-3,4-bis(trichloromethyl)-2 H-3,4-dihydrobenzopyran-2-one and hydrochloride DMAC. Recombination of ·CCl 3 radicals yields hexachloroethane. The ratio of the products depends on the reaction conditions (the concentration of DMAC, the light intensity and the temperature). The primary step in the mechanism of the sensitization of CCl 4 is assumed to be the formation of the excited state, charge transfer (CT) complex of the type DMAC δ+…CCl 4 δ−. Chloromethanes CH x Cl 4− x ( x = 0,1,2) quench the fluorescence of DMAC and MAC. The Stern—Volmer constant for MAC is related to the electron affinity of chloromethanes.

Free radical chain reactions of ate complexes. Electron transfer processes 42

AbstractIodide ion promotes the free radical reaction of isopropylmercury idide with bromotrichloromethane to yield isopropyl bromide with rate enhancement in the order of 104. The reaction involves electron transfer from i‐PrHgI2− to the trichloromethyl radical in a long kinetic chain process. Iodide ion also promotes the free radical chain conjugate addition of tert‐butylmercury chloride to α,β‐unsaturated ketones, esters, phosphonate esters and sulfones. Competitive reactivity studies indicate that lithium di‐tert‐butylcuprates or tri‐tert‐butylzincates react with 2‐cycloalkenones by a mechanism involving attack by tert‐butyl radicals. No evidence for radical attack is observed for the corresponding n‐butyl ate complexes of copper or zinc.

Ethanol feeding stimulates trichloromethyl radical formation from carbon tetrachloride in liver.

1. Female, Sprague-Dawley rats were fed liquid ethanol or control diets, both of which contained fat either at 35% (high fat, HF) or 12% (low fat, LF) of total calories. The rats were given an oral dose of 13CCl4 along with the spin trapping agent, phenyl tert.-butyl-nitrone (PBN). 2. Analysis of the hepatic lipid extracts revealed a signal due to the trichloromethyl radical (CCl3) adduct of PBN. Ethanol feeding in the HF diet increased the signal intensity two-fold over controls, whereas ethanol feeding in the LF diet caused only a 35% increase. 3. In isolated microsomes, ethanol feeding in HF or LF diets increased CCl3 formation by approx. 8-fold and 4-fold, respectively, over control values. These data support the hypothesis that ethanol induces a cytochrome P-450 isozyme that is highly active in the metabolism of CCl4 to the CCl3 radical. 4. Ethanol feeding markedly enhanced the hepatotoxicity of CCl4; however, there were no differences in the loss of hepatic enzymes into blood between the ethanol plus HF or ethanol plus LF groups. Thus, ethanol is likely to increase CCl4 toxicity by some mechanism in addition to increased trichloromethyl radical formation.