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PubMed2005

Allotopic expression of a mitochondrial alternative oxidase confers cyanide resistance to human cell respiration.

Human mitochondrial respiration is distinct from that of most plants, microorganisms and even some metazoans in that it reduces molecular oxygen only through the highly cyanide-sensitive enzyme cytochrome c oxidase. Here we show that expression of the cyanide-insensitive alternative oxidase (AOX), recently identified in the ascidian Ciona intestinalis, is well tolerated by cultured human cells and confers spectacular cyanide resistance to mitochondrial substrate oxidation. The expressed AOX seems to be confined to mitochondria. AOX involvement in electron flow is triggered by a highly reduced redox status of the respiratory chain (RC) and enhanced by pyruvate; otherwise, the enzyme remains essentially inactive. AOX expression promises to be a valuable tool to limit the deleterious consequences of RC deficiency in human cells and whole animals.

Animals↗

PubMed1998

Determination of cyanide by a flow injection analysis-atomic absorption spectrometric method.

A new flow injection analysis (FIA) procedure is proposed for the indirect atomic absorption spectrometric determination of cyanide. The FIA manifold is based on the insertion of the sample into a distilled water carrier, then the sample flows through a solid-phase reactor filled with silver iodide entrapped in polymeric resin beads. The calibration graph is linear over the range 0.2-6.0 mg l-1 of cyanide (correlation coefficient 0.9974), the detection limit is 0.1 mg l-1, the sample throughput is 193 h-1 and the RSD is 0.8%. The method is simple, quick and more selective than other published FIA procedures. The reproducibility obtained by using different solid-phase reactors and solutions is in the range 2.2-3.1% (RSD). The method was applied to the determination of cyanide in commercial samples such as pharmaceutical formulations and industrial electrolytic baths.

Cyanides↗

PubMed2004

Bi- and poly-metallic cyanide-bridged complexes of the redox-active cyanomanganese nitrosyl unit [Mn(CN)(PR3)(NO)(eta-C5H4Me)].

Cationic nitrile complexes and neutral halide and cyanide complexes, with the general formula [MnL1L2(NO)(eta-C5H4Me)]z, undergo one-electron oxidation at a Pt electrode in CH2Cl2. Linear plots of oxidation potential, Eo', vs. nu(NO) or the Lever parameters, EL, for L1 and L2, allow Eo' to be estimated for unknown analogues. In the presence of TlPF6, [MnIL'(NO)(eta-C5H4Me)] reacts with [Mn(CN)L(NO)(eta-C5H4Me)] to give [(eta5-C5H4Me)(ON)LMn(mu-CN)MnL'(NO)(eta5-C5H4Me)][PF6] which undergoes two reversible one-electron oxidations; DeltaE, the difference between the potentials for the two processes, differs significantly for stable cyanide-bridged linkage isomers. Novel pentametallic complexes such as [Mn[(mu-NC)Mn(CNBut)(NO)(eta5-C5H4Me)]4(OEt2)][PF6]2 and [Mn[(mu-NC)Mn(CNXyl)(NO)(eta5-C5H4Me)]4(NO3-O,O')][PF6], containing a trigonal bipyramidal and a distorted octahedral Mn(II) centre, respectively, result either from slow decomposition of the binuclear cyanide-bridged species or from the reaction of anhydrous MnI2 with four equivalents of [Mn(CN)L(NO)(eta5-C5H4Me)] in the presence of TlPF6.

Bridged-Ring Compounds↗

PubMed1974

Electron-paramagnetic-resonance studies on cobalt(II) carbonic anhydrase. Low-spin cyanide complexes.

The low-spin cyanide complexes of three Co(II) carbonic anhydrases were investigated by electron paramagnetic resonance (e.p.r.) at 9 and 35GHz. Well-defined and closely axial spectra were obtained only in the absence of oxygen. Several mole equivalents of cyanide were required for complete formation of the complexes in frozen solution, although large excesses caused abstraction of the cobalt. Experiments with [(13)C]cyanide showed that the low-spin complexes contained two CN(-) groups in an environment similar to that of the in-plane ligands in [Co(CN)(5)](3-). A combined e.p.r. and spectrophotometric titration confirmed the presence of two CN(-) ligands. A 5-co-ordinate square pyramidal structure involving three protein ligands was proposed. The dicyanide complex could be oxygenated reversibly, producing a characteristic new e.p.r. spectrum. The O(2) molecule was thought to occupy the remaining octahedral metal site in a formally Co(III) species. The optical spectrum of the dicyanide lacked the prominent d-d bands of the high-spin monocyanide. Both e.p.r. and optical data indicated that the low-spin complex was formed much more fully in frozen solution than at room temperature. Differences in behaviour between the high- and low-activity enzymes suggested some variation in conformational flexibility at the metal binding site.

Anaerobiosis↗

PubMed1978

Cyanide-insensitive oxidation of ascorbate + NNN'N'-tetramethyl-p-phenylenediamine mixture by mung-bean (Phaseolus aureus) mitochondria. An energy-linked function.

Freshly prepared washed or purified mung-bean (Phaseolus aureus) mitochondria utilize oxygen with ascorbate/tetramethyl-p-phenylenediamine mixture as electron donor in the presence of KCN. ATP control of the oxygen uptake can be observed with very fresh mitochondria. The electron flow, which is inhibited by antimycin A, salicylhydroxamic acid or octylguanidine, takes place by reversed electron transport through phosphorylation site II and thence to oxygen through the cyanide-insensitive pathway. Oligomycin and low concentrations of uncoupler partially inhibit the oxygen uptake in a manner similar to that observed for other energy-linked functions of plant mitochondria. An antimycin A-insensitive oxygen uptake occurs if high concentrations of uncoupler are used, indicating that the pathway of electron flow has been altered. The process of cyanide-insensitive ascorbate oxidation is self-starting, and, since it occurs in the presence of oligomycin, it is concluded that the reaction can be energized by a single energy-conservation site associated with the cyanide-insensitive oxidase pathway.

Ascorbic Acid↗

PubMed1984

Cyanide inhibition of cytochrome c oxidase. A rapid-freeze e.p.r. investigation.

The inhibition of cytochrome c oxidase by cyanide, starting either with the resting or the pulsed enzyme, was studied by rapid-freeze quenching followed by quantitative e.p.r. It is found that a partial reduction of cytochrome oxidase by transfer of 2 electron equivalents from ferrocytochrome c to cytochrome a and CuA will induce a transition from a closed to an open enzyme conformation, rendering the cytochrome a3-CuB site accessible for cyanide binding, possibly as a bridging ligand. A heterogeneity in the enzyme is observed in that an e.p.r. signal from the cytochrome a3 3+-HCN complex is only found in 20% of the molecules, whereas the remaining cyanide-bound a3-CuB sites are e.p.r.-silent.

Binding Sites↗

PubMed1994

Electron-paramagnetic-resonance and magnetic-circular-dichroism studies of the binding of cyanide and thiols to the thiols to the iron-molybdenum cofactor from Klebsiella pneumoniae nitrogenase.

FeMoco, a low-M(r) metal cluster of probable composition Fe7MoS9 complexed with homocitrate, has been extracted with N-methylformamide from the MoFe protein of the nitrogenase enzyme from Klebsiella pneumoniae. The binding of cyanide and thiols to the FeMoco cluster in its paramagnetic S = 3/2 oxidation level has been studied by low-temperature e.p.r. and magnetic-circular-dichroism (m.c.d.) spectroscopies. Cyanide binds to isolated FeMoco at more than one site, and causes changes in the g values form g = 4.6, 3.2, 2.0 to g = 4.29, 3.82, 2.02 E.p.r. competition studies indicate that one cyanide can be displaced by thiolate from one type of site. The form of the low-temperature m.c.d. spectrum is little changed by ligand binding, thus the basic cluster structure remains intact. However, when benzenethiol is bound, a new intense band (lambda 387 nm) is observed, indicating the generation of an increased ligand-to-cluster charge-transfer interaction.

Circular Dichroism↗

PubMed1994

Thermodynamics of hydrogen cyanide and hydrogen fluoride binding to cytochrome c peroxidase and its Asn-82-->Asp mutant.

The thermodynamics of binding of fluoride and cyanide to cytochrome c peroxidase (CCP) and its Asn-82-->Asp mutant (D82CCP) in phosphate and acetate buffer at an ionic strength of 0.15 mol.kg-1 from pH 5.0 to 7.1 were investigated by titration calorimetry at 289 and 297 K. The binding reactions are enthalpically driven. The fluoride-binding constants determined from the titration calorimetry results were in agreement with those determined from difference-spectroscopy measurements. For cyanide binding to CCP at 297.9 K, the binding constant decreased from 8.95 (+/- 0.83) x 10(5) M-1 at pH 7.0 to 4.04(+/- 0.23) x 10(5) M-1 at pH 5.0, and the binding enthalpy increased from -57.2 +/- 1.4 kJ.mol-1 at pH 7.0 to -48.6 +/- 1.8 kJ.mol-1 at pH 5.0. For fluoride binding to CCP, the binding constant increased from 8.41(+/- 0.54) x 10(3) M-1 at pH 7.0 to 3.11(+/- 0.09) x 10(5) M-1 at pH 5.0 and the binding enthalpy increased from -71.9 +/- 1.1 kJ.mol-1 at pH 7.0 to -67.0 +/- 1.9 kJ.mol-1 at pH 5.0. The binding enthalpies for D82CCP were about the same as those for CCP. However, the binding constants for cyanide and fluoride to D82CCP were respectively a factor of two less and at least an order of magnitude less than the corresponding binding constants of CCP. Decreased ligand-binding strength in the D82CCP mutant is thus entirely due to entropic effects.

Asparagine↗

PubMed1999

The structures of the horseradish peroxidase C-ferulic acid complex and the ternary complex with cyanide suggest how peroxidases oxidize small phenolic substrates.

We have solved the x-ray structures of the binary horseradish peroxidase C-ferulic acid complex and the ternary horseradish peroxidase C-cyanide-ferulic acid complex to 2.0 and 1.45 A, respectively. Ferulic acid is a naturally occurring phenolic compound found in the plant cell wall and is an in vivo substrate for plant peroxidases. The x-ray structures demonstrate the flexibility and dynamic character of the aromatic donor binding site in horseradish peroxidase and emphasize the role of the distal arginine (Arg(38)) in both substrate oxidation and ligand binding. Arg(38) hydrogen bonds to bound cyanide, thereby contributing to the stabilization of the horseradish peroxidase-cyanide complex and suggesting that the distal arginine will be able to contribute with a similar interaction during stabilization of a bound peroxy transition state and subsequent O-O bond cleavage. The catalytic arginine is additionally engaged in an extensive hydrogen bonding network, which also includes the catalytic distal histidine, a water molecule and Pro(139), a proline residue conserved within the plant peroxidase superfamily. Based on the observed hydrogen bonding network and previous spectroscopic and kinetic work, a general mechanism of peroxidase substrate oxidation is proposed.

Binding Sites↗

PubMed1975

Solvent extraction of cadmium from alkaline cyanide solutions with quaternary amines.

Quaternary amines are unique in their ability to extract metal cyanides from highly alkaline solutions. Cadmium cyanide extracts essentially quantitatively at both the subnanogram and macro levels. Regeneration of the amine solvent is achieved by stripping the cadmium with sodium hydroxide, sodium hypochlorite, or alkaline or acidic formaldehyde solutions. Because they readily extract free cyanide as well as anionic metab cyano complexes, the high-molecular-weight quaternary amines show considerable promise for industrial pollution abatement applications.

Alkalies↗

PubMed2004

Combination of cassava flour cyanide and urinary thiocyanate measurements of school children in Mozambique.

The maximum daily cassava flour intake of children may be calculated from determination of the total cyanide content of cassava flour and urinary thiocyanate levels of school children in samples collected at the same time and place. Four sites, two with and two without recent konzo cases, were chosen for study. In two sites with recent konzo cases, 84% and 93% of school children consumed cassava the previous day, and the calculated maximum daily consumption of cassava was over 700 g. In two sites without recent konzo cases, about 50% of school children consumed cassava the previous day and the calculated daily consumption of cassava flour was less than 150 g. By measurements of cyanide in flour and urinary thiocyanate we are therefore able to distinguish between communities whose diet is almost totally reliant on cassava, and who are therefore susceptible to konzo, and those who have a broader diet and are free from konzo. In another calculation it is shown that 4-23% of the essential S-containing amino acids in the cassava flour consumed by children is used up to detoxify and flour cyanide to thiocyanate. This depletion of methionine and cystine may leads to protein deficiency and may contribute to onset of konzo.

Child↗

PubMed2001

Cyanide-resistant alternative respiration is strictly correlated to intracellular peroxide levels in Acremonium chrysogenum.

A strict correlation between the intensity of the cyanide-resistant alternative respiratory pathway and the intracellular peroxide levels in the cephalosporin C producer filamentous fungus Acremonium chrysogenum was demonstrated. Intracellular peroxide levels increased in a dose-dependent manner after addition of H2O2 to the culture media. A similar phenomenon was observed due to the specific inhibition of catalase by salicylic acid. In both cases, cyanide-resistant respiration was markedly stimulated. On the other hand, both cyanide-resistant respiration and intracellular peroxide levels were effectively suppressed by the lipid peroxyl radical scavenger DL-alpha-tocopherol, which breaks lipid peroxidation chains effectively. Our findings firmly supported the assumption that there is a connection between the intracellular peroxide levels and the intensity of the alternative respiratory pathway in fungi.

Acremonium↗

PubMed2002

Acute cyanide intoxication treated with a combination of hydroxycobalamin, sodium nitrite, and sodium thiosulfate.

An 80-year-old diabetic patient was admitted to the hospital because of sudden unconsciousness and severe metabolic acidosis. His son reported the possibility of cyanide poisoning. Clinical data and the detection of cyanide in blood and gastric material confirmed this possibility. Supportive therapy and the following antidotes--sodium nitrite two doses 300 mg i.v., sodium thiosulfate 3 g i.v., and hydroxocobalamin 4 g in 24 hours--were administered immediately and the patient completely recovered in 48 hours. Our observations suggest that timely and appropriate use of antidotes for cyanide intoxication may prevent death, even in aged diabetic patients.

Acidosis↗

PubMed1952

The intracellular growth of bacteriophages. I. Liberation of intracellular bacteriophage T4 by premature lysis with another phage or with cyanide.

A method is described for liberating and estimating intracellular bacteriophage at any stage during the latent period by arresting phage growth and inducing premature lysis of the infected cells. This is brought about by placing the infected bacteria into the growth medium supplemented with 0.01 M cyanide and with a high titer T6 lysate. It was found in some of the later experiments that the T6 lysate is essential only during the first half of the latent period. Cyanide alone will induce lysis during the latter part of the latent period. Using this method on T4-infected bacteria it is found that during the first half of the latent period no phage particles, not even those originally infecting the bacteria, are recovered. This result is in agreement with the gradually emerging concept that a profound alteration of the infecting phage particle takes place before reproduction ensues. During the second half of the latent period mature phage is found to accumulate within the bacteria at a rate which is parallel to the approximately linear increase of intracellular DNA in this system. However, the phage production lags several minutes behind DNA production. When 5-methyltryptophan replaced cyanide as the metabolic inhibitor, similar results were obtained. The curves were, however, displaced several minutes to the left on the time axis. The results are compared with Latarjet's (16) data on x-radiation of infected bacteria and with Foster's data (18) concerning the effect of proflavine on infected bacteria. Essential agreement with both is apparent.

Bacteria↗

PubMedDate not supplied

Cyanide in blood by gas chromatography with NP detector and acetonitrile as internal standard. Application on air accident fire victims.

An improved gas chromatographic method for HCN in blood with acetonitrile as an internal standard has been developed. The necessity to test for cyanide on samples from air accident fire victims is discussed in view of the fact that carbon monoxide measurements usually do not correlate with cyanide findings. Nine cases (out of 67), with blood CO saturation of less than 20% and cyanide concentration over 2 mg/L, are described.

Accidents, Aviation↗

PubMedDate not supplied

Results of a multilaboratory checksample analysis program for carbon monoxide and cyanide.

A blind check sample analysis program, designed to evaluate global performance in the determination of fire-related analytes (carbon monoxide and cyanide), was implemented and processed using 10 field forensic toxicology laboratories. Each participant received, on a quarterly basis, a set of four calibrators and a set of four unknown check samples. Each participant was asked to determine the presence and quantity of carbon monoxide (carboxyhemoglobin in percent saturation of hemoglobin units) and cyanide (in mg/L units), using the calibrators for reference. The results were to be reported in an anonymous manner. Prior to and during the analysis period all batches of calibrators and check samples were validated for analyte stability using gas chromatography, CO- oximetry, and ion chromatography. The performance of the laboratories in the analysis of carboxyhemoglobin was evaluated over a concentration range of 3 to 40% saturation yielding a correlation with validation concentrations of 0.986. In some cases, false negatives and false positives were reported. The performance of laboratories in the analysis of cyanide was evaluated over a concentration range of 0.1 to 2.5 mg/L. Laboratory results yielded a correlation of 0.443 with validated concentrations. False negatives and false positives were also reported. Based upon the correlation estimates, it was concluded that forensic toxicology laboratories are likely to generate reliable carboxyhemoglobin data.

Calibration↗

PubMed2005

Determination of acetonitrile and cyanide in rat blood: application to an experimental study.

Methods were developed for the analysis of acetonitrile and its metabolite cyanide in the blood of rats exposed to acetonitrile. Acetonitrile was analyzed by the headspace technique coupled to gas chromatography with detection by flame ionization, and cyanide was analyzed by high-performance liquid chromatography with fluorescence detection (lambdaex = 418 nm and lambdaem = 460 nm) after derivatization of the ion with naphthalene 2,3-dicarboxyaldehyde and taurine. The quantitation limits of the methods for the analysis of acetonitrile and cyanide were 4.875 microg/mL and 0.025 microg/mL, respectively. The coefficients of variation of 10% or less obtained for intra- and interassay precision indicate the precision of these analytical methods and the systematic errors, all less than 5%, indicate that the methods are quite accurate. The methods were applied to an experimental study after the animals received acetonitrile at the doses of 2 mmol/kg or 5 mmol/kg.

Acetonitriles↗

PubMed1994

Time to discontinue the use of solutions A and B as a cyanide 'antidote'.

Solutions A and B (15.8% ferrous sulfate in 0.3% citric acid and 6% sodium carbonate, respectively) have been available as a first-aid treatment for cyanide ingestion for many decades. Controversy surrounding the efficacy of solutions A and B has existed for much of that time, the main protagonists being in the UK. The current opinion in the UK is that solutions A and B should no longer be used as a first-aid measure in the management of cyanide poisoning. Similarly, oral sodium thiosulfate or activated charcoal should not be used. The recommended first-aid treatment of symptomatic cyanide poisoning is 100% oxygen and amyl nitrite, irrespective of the route of exposure.

Antidotes↗