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At least 379 records · Page 21Linked to original sources
PubMed1998

Holmium:YAG lithotripsy: photothermal mechanism converts uric acid calculi to cyanide.

PURPOSE: Holmium:YAG lithotripsy fragments stones through a photothermal mechanism. Uric acid when heated is known to be converted into cyanide. We test the hypothesis that holmium: YAG lithotripsy of uric acid calculi produces cyanide. MATERIALS AND METHODS: Human calculi of known uric acid composition were irradiated with holmium:YAG energy in water. Stones received a total holmium:YAG energy of 0 (control), 0.1, 0.25, 0.5, 0.75, 1.0 or 1.25 kJ. The water in which lithotripsy was performed was analyzed for cyanide concentration. A graph was constructed to relate holmium:YAG energy to cyanide production. RESULTS: Holmium:YAG lithotripsy of uric acid calculi in vitro produced cyanide consistently. Cyanide production correlated with total holmium:YAG energy (p <0.001). CONCLUSIONS: Holmium:YAG lithotripsy of uric acid calculi risks production of cyanide. This study raises significant safety issues.

Aluminum Silicates↗
PubMed2003

Changes in zooxanthellae density, morphology, and mitotic index in hermatypic corals and anemones exposed to cyanide.

Sodium cyanide (NaCN) is widely used for the capture of reef fish throughout Southeast Asia and causes extensive fish mortality, but the effect of NaCN on reef corals remains debated. To document the impact of cyanide exposure on corals, the species Acropora millepora, Goniopora sp., Favites abdita, Trachyphyllia geoffrio, Plerogyra sp., Heliofungia actinformis, Euphyllia divisa, and Scarophyton sp., and the sea anemone Aiptasia pallida were exposed to varying concentrations of cyanide for varying time periods. Corals were exposed to 50, 100, 300, and 600 mg/l of cyanide ion (CN(-)) for 1-2 min (in seawater, the CN(-) forms hydrocyanic acid). These concentrations are much lower than those reportedly used by fish collectors. Exposed corals and anemones immediately retracted their tentacles and mesenterial filaments, and discharged copious amounts of mucus containing zooxanthellae. Gel electrophoreses techniques found changes in protein expression in both zooxanthellae and host tissue. Corals and anemones exposed to cyanide showed an immediate increase in mitotic cell division of their zooxenthellae, and a decrease in zooxanthellae density. In contrast, zooxanthellae cell division and density remained constant in controls. Histopathological changes included gastrodermal disruption, mesogleal degradation, and increased mucus in coral tissues. Zooxanthellae showed pigment loss, swelling, and deformation. Mortality occurred at all exposure levels. Exposed specimens experienced an increase in the ratio of gram-negative to gram-positive bacteria on the coral surface. The results demonstrate that exposure cyanide causes mortality to corals and anemones, even when applied at lower levels than that used by fish collectors. Even brief exposure to cyanide caused slow-acting and long-term damage to corals and their zooxanthellae.

Animals↗
PubMedDate not supplied

Cyanide in human disease: a review of clinical and laboratory evidence.

Experimental cyanide exposure in animals causes demyelination and circumstantial clinical and laboratory evidence suggest that there are human parallels. In Leber's hereditary optic atrophy there appears to be a defect in the conversion of cyanide to thiocyanate because of deficient rhodanese activity. For transmitters of the disease smoking carries the risk of blindness and in the most severely affected patients, there is diffuse neurological disease. It is possible that other hereditary optic atrophies (dominant and recessive) may also reflect inborn errors of cyanide metabolism. In the retrobulbar neuritis and optic atrophy of vitamin B12 deficiency there may be a conditional abnormality of cyanide metabolism in smokers, and likewise in so-called tobacco-alcohol amblyopia in which there are more complex nutritional deficiencies. Epidemiological evidence (differing sex ratios, excess of smokers) indicates that defective cyanide metabolism may contribute to the development of sub-acute combined degeneration of the cord in vitamin B12 deficiency. In protein-malnourished populations consuming large amounts of cyanide or cyanogens, viz. in tropical Africa where the staple diet includes cassava containing large amounts of linamarin, similar maladies occur as acquired disorders. There may be a similar explanation for lathyrism. The known pathways of human cyanide metabolism are reviewed and evidence supporting the clinical data is presented.

Adolescent↗
PubMed2000

Differential effects of chronic cyanide intoxication on heart, lung and pancreatic tissues.

The histotoxic effects of chronic cyanide insult on heart, lung and pancreatic tissues, and some corroborative enzyme and metabolite changes were studied in New Zealand White rabbits using colorimetric, enzymatic and histochemical methods. Two groups of rabbits were fed for 10 months on either pure growers mash or grower mash +702 ppm inorganic cyanide. There were no significant differences in time-course profiles of serum amylase and fasting blood glucose between the cyanide-fed group and control. Pancreatic islet and heart histologies showed no pathological changes, and there were no significant differences in both serum and heart aspartate transaminase activities between the two groups. However, there were significant decreases (P<0.01) in alkaline phosphatase activity in the lungs of the cyanide-fed group, with corresponding significant (P<0.05) increases in the serum activity of the enzyme. Histological examination of lung tissue of the cyanide-treated rabbits revealed focal areas of pulmonary oedema and necrosis. These results suggest the existence of variabilities in tissue susceptibilities to the toxic effect of chronic cyanide exposure. It would appear that chronic cyanide exposure may not predispose to diabetes in the presence of adequate protein intake.

Alkaline Phosphatase↗
PubMed2002

Melatonin attenuates brain mitochondria DNA damage induced by potassium cyanide in vivo and in vitro.

The effect of potassium cyanide on mitochondria DNA (mtDNA) in mouse brain was investigated in vivo and in vitro. When potassium cyanide (0, 0.1, 1.0 or 2.0 mM) was incubated with a crude mitochondria fraction prepared from mouse brain at 37 degrees C for 60 min, the damage of mtDNA was observed in a concentration-dependent manner. However, the mtDNA damage was prevented by a co-treatment with melatonin (1.5 mM), a scavenger of hydroxyl radicals (*OH). Furthermore, a subcutaneous injection of potassium cyanide (7mg/kg) caused both brain mtDNA damage and severe seizures in mouse. The damage of mtDNA and seizures induced by potassium cyanide were abolished by the pre-injection of melatonin (20 mg/kg). Hydrogen peroxide (1.5 mM) inflicted damage to brain mtDNA in the presence of Fe(2+) (3.0 microM). The damage was abolished by the co-treatment with melatonin. Furthermore, when cyanide (0, 0.1 or 1.0 mM) was incubated with the crude mitochondria fraction prepared from mouse brain, the lipid peroxidation was significantly increased in a concentration-dependent manner. The increased lipid peroxidation was completely inhibited by the co-treatment with melatonin (1.0 mM). These results suggest that reactive oxygen species including the *OH may play a cardinal role for mtDNA damage induced by potassium cyanide. Hence, the present study concluded that melatonin protects against DNA damage induced by the *OH produced by cyanide or hydrogen peroxide.

Animals↗
PubMed2003

The cyanide hydratase enzyme of Fusarium lateritium also has nitrilase activity.

The filamentous fungus Fusarium lateritium produces cyanide hydratase when grown in the presence of cyanide. The cyanide hydratase protein produced at a high level in Escherichia coli shows a low but significant nitrilase activity with acetonitrile, propionitrile and benzonitrile. The nitrilase activity is sufficient for growth of the recombinant strain on acetonitrile, propionitrile or benzonitrile as the sole source of nitrogen. The recombinant enzyme shows highest nitrilase activity with benzonitrile. Site-directed mutagenesis of the F. lateritium cyanide hydratase gene indicates that mutations leading to a loss of cyanide hydratase activity also lead to a loss of nitrilase activity. This suggests that the active site for cyanide hydratase and nitrilase activity in the protein is the same. This is the first evidence of cyanide hydratase having nitrilase activity.

Amino Acid Sequence↗
PubMed1998

Effect of piperonyl butoxide or allopurinol on cyanide-induced lipid peroxidation in mouse brain.

The effect of piperonyl butoxide or allopurinol on cyanide-induced lipid peroxidation was investigated using homogenates from whole brain of mice. The brain homogenate exposed to a low concentration of potassium cyanide (10, 50, or 100 microM) was significantly increased in their concentration of malondialdehyde (MDA) + 4-hydroxyalkenals (4-MDA) as compared to control samples, in a concentration-dependent manner. The increased lipid peroxidation induced by cyanide was inhibited by piperonyl butoxide (1 mM), an inhibitor of mixed function oxidase, but not by allopurinol (0.1 mM), an inhibitor of xanthine oxidase. Furthermore, when a brain homogenate heated at 86 degrees C for 1 min was incubated with or without cyanide at 37 degrees C for 20 min, MDA + 4-MDA levels in the homogenate were not changed between cyanide treatment and untreated. An intraperitoneal injection of piperonyl butoxide (1 g/kg) significantly inhibited cyanide-induced seizures in mice. These results suggest that cyanide-induced seizures may be partly involved in the lipid peroxidation produced by the heat unstable and piperonyl butoxide dependent factors in brain.

Allopurinol↗
PubMed2003

Destruction of cyanide waste solutions using chlorine dioxide, ozone and titania sol.

Increasingly, there are severe environmental controls in the mining industry. Because of lack of technological advances, waste management practices are severely limited. Most of the wastes in the milling industrial effluents are known to contain cyanides and it is recognized that after extraction and recovery of precious metals, substantial amounts of cyanide are delivered to tailings ponds. The toxicity of cyanide creates serious environmental problems. In this paper we describe several methods for the treatment of cyanide solutions. These include: (1) cyanide destruction by oxidation with chlorine dioxide (ClO(2)) in a Gas-Sparged Hydrocyclone (GSH) reactor; (2) destruction of cyanide by ozone (O(3)) using a stirred batch reactor, and finally, (3) the photolysis of cyanide with UV light in presence of titania sol. In all cases excellent performance were observed as measured by the extent and of the destruction.

Chlorine Compounds↗
PubMed1998

Determination of cyanide in whole blood by capillary gas chromatography with cryogenic oven trapping.

Cyanide, one of the most important toxic substances, has been found measurable with high sensitivity by capillary gas chromatography (GC) with cryogenic oven trapping upon injection of headspace (HS) vapor samples. The entire amount of cyanide in the HS sample could be cryogenically trapped prior to on-line GC analysis. A 0.5-mL volume of blood in the presence or absence of cyanide and propionitrile (internal standard, IS) was added to a vial containing 0.25 mL of distilled water, 0.3 g of Na2-SO4, 0.2 mL of 50% H3PO4, and 0.1 g of ascorbic acid (when needed), and the mixture was heated at 70 degrees C for 15 min. A 5-mL volume of the HS vapor was introduced into a GC capillary column in the splitless mode at -30 degrees C oven temperature that was programmed up to 160 degrees C for GC analysis with nitrogen-phosphorus detection. A sharp peak was obtained for cyanide under the present conditions, and backgrounds were very clean. The extraction efficiencies of cyanide and IS were 2.89-3.22 (100 or 500 ng/mL) and 2.42%, respectively. The calibration curve showed good linearity in the range of 25-1000 ng/mL and the detection limit was approximately 2 ng/mL. The coefficients of intraday and interday variations were 2.9 and 11.8%, respectively. The mean blood cyanide level measured for actual fire victims was 687 +/- 597 ng/mL (mean +/- SD, n = 9). Endogenous blood cyanide concentration for healthy subjects was 8.41 +/- 3.09 ng/mL (mean +/- SD, n = 6).

Chromatography, Gas↗
PubMed2003

Cyanide binding to cytochrome c peroxidase (H52L).

Cyanide binding to a cytochrome c peroxidase (CcP) variant in which the distal histidine has been replaced by a leucine residue, CcP(H52L), has been investigated as a function of pH using spectroscopic, equilibrium, and kinetic methods. Between pH 4 and 8, the apparent equilibrium dissociation constant for the CcP(H52L)/cyanide complex varies by a factor of 60, from 135 microM at pH 4.7 to 2.2 microM at pH 8.0. The binding kinetics are biphasic, involving bimolecular association of the two reactants, followed by an isomerization of the enzyme/cyanide complex. The association rate constant could be determined up to pH 8.9 using pH-jump techniques. The association rate constant increases by almost 4 orders of magnitude over the pH range investigated, from 1.8 x 10(2) M(-1) s(-1) at pH 4 to 9.2 x 10(5) M(-1) s(-1) at pH 8.6. In contrast to wild-type CcP, where the binding of HCN is the dominant binding pathway, CcP(H52L) preferentially binds the cyanide anion. Above pH 8, cyanide binding to CcP(H52L) is faster than cyanide binding to wild-type CcP. Cyanide dissociates 4 times slower from the mutant protein although the pH dependence of the dissociation rate constant is essentially identical for CcP(H52L) and CcP. Isomerization of the CcP(H52L)/cyanide complex is observed between pH 4 and 8 and stabilizes the complex. The isomerization rate constant has a similar magnitude and pH dependence as the cyanide dissociation rate constant, and the two reactions are coupled at low cyanide concentrations. This isomerization has no counterpart in the wild-type CcP/cyanide complex.

Amino Acid Substitution↗
PubMed1996

Unusual affinity of cyanide for ferrous and ferric Scapharca inaequivalvis homodimeric hemoglobin. Equilibria and kinetics of the reaction.

The homodimeric hemoglobin from the mollusk Scapharca inaequivalvis (HbI) yields very stable ferrous and ferric cyanide adducts. The stability of the ferrous complex is particularly unusual such that it enabled determination of the spectroscopic properties of the complex and the characterization of the cyanide binding reaction to deoxygenated HbI at equilibrium and kinetically. The absorption spectrum of the ferrous cyanide complex is typical of a low-spin derivative; in the near-infrared region, it displays two bands at 695 and 840 nm attributable to charge transfer transitions. At pH 9.2, cyanide binds to deoxy HbI with no cooperativity and an apparent affinity constant of 17 M-1, which is about 10-fold higher than that for deoxy horse heart myoglobin. The rate of cyanide dissociation from both the ferrous and the ferric HbI adducts is slow relative to those of the other hemoproteins investigated to date and provides the major contribution to the unusual affinity for the ligand. The rate of cyanide binding to the ferric protein, in which the pentacoordinate derivative is the dominant species, is about 100-fold faster relative to that of the ferrous protein. In structural terms, the high affinity for cyanide of Scapharca hemoglobin has been ascribed to the decreased overall polarity of the heme pocket which is related to the localization of the heme groups at the subunit interface.

Animals↗
PubMed2002

Depletion of host-derived cyanide in the gut of the eastern tent caterpillar, Malacosoma americanum.

Using a colorimetric procedure, we assessed the HCN-p of black cherry leaves (Prunus serotina) ingested by the eastern tent caterpillar, Malacosoma americanum, and the cyanide content of the bolus as it passed thorough the caterpillar's digestive tract and into the detritus pool. The mean HCN-p of leaves in our study area was 1902 +/- 174 (SE) ppm. Young leaves found at the tips of growing branches, which the caterpillars preferred, had a significantly higher HCN-p (3032 +/- 258 ppm) than older leaves found at the middle (1542 +/- 243 ppm) or base of the shoot (1131 +/- 159 ppm). Following a bout of overnight feeding on young leaves, the cyanide content of the foregut and midgut boluses of early sixth-instar caterpillars averaged 631 +/- 161 ppm, and 14 +/- 3 ppm, respectively, indicating that host-derived cyanide is rapidly depleted as the bolus transits the gut. Some cyanide, however, remains. In three studies, the mean cyanide content of fresh fecal pellets ranged from approximately 20 to 38 ppm, while the dried, compacted pellets ranged from 63 to 85 ppm. Food in the foreguts of mature caterpillars dispersing over the ground in search of pupation sites had 417 +/- 99 ppm cyanide. The potential impact of this egested and caterpillar-transported cyanide on the consumer and detritivore communities is discussed.

Animals↗
PubMed2004

Calcineurin-mediated Bad translocation regulates cyanide-induced neuronal apoptosis.

In cyanide-induced apoptosis, an increase in cytosolic free Ca2+ and generation of reactive oxygen species are initiation stimuli for apoptotic cell death. Previous studies have shown that cyanide-stimulated translocation of Bax (Bcl-associated X protein) to mitochondria is linked with release of cytochrome c and subsequent activation of a caspase cascade [Shou, Li, Prabhakaran, Borowitz and Isom (2003) Toxicol. Sci. 75, 99-107]. In the present study, the relationship of the cyanide-induced increase in cytosolic free Ca2+ to activation of Bad ( Bcl-2/Bcl-X(L)- antagonist, causing cell death) was determined in cortical cells. Bad is a Ca2+-sensitive pro-apoptotic Bcl-2 protein, which on activation translocates from cytosol to mitochondria to initiate cytochrome c release. In cultured primary cortical cells, cyanide produced a concentration- and time-dependent translocation of Bad from cytosol to mitochondria. Translocation occurred early in the apoptotic response, since mitochondrial Bad was detected within 1 h of cyanide treatment. Mitochondrial levels of the protein continued to increase up to 12 h post-cyanide exposure. Concurrent with Bad translocation, a Ca2+-sensitive increase in cellular calcineurin activity was observed. Increased cytosolic Ca2+ and calcineurin activation stimulated Bad translocation since BAPTA [bis-(o-aminophenoxy)ethane-N, N, N', N'-tetra-acetic acid], an intracellular Ca2+ chelator, and cyclosporin A, a calcineurin inhibitor, significantly reduced translocation. BAPTA also blocked release of cytochrome c from mitochondria as well as apoptosis. Furthermore, treatment of cells with the calcineurin inhibitors cyclosporin A or FK506 blocked the apoptotic response, linking calcineurin activation and the subsequent translocation of Bad to cell death. These observations show that by inducing a rapid increase in cytosolic free Ca2+, cyanide can partially initiate the apoptotic cascade through a calcineurin-mediated translocation of Bad to mitochondria.

Animals↗
PubMed2005

Alkaline cyanide biodegradation by Pseudomonas pseudoalcaligenes CECT5344.

Pseudomonas pseudoalcaligenes CECT5344 uses cyanide, cyanate, beta-cyanoalanine, and other cyanoderivatives as nitrogen sources under alkaline conditions, which prevents volatile HCN (pK(a) 9.2) formation. The cyanide consumed by this strain is stoichiometrically converted into ammonium. In addition, this bacterium grows with the heavy metal, cyanide-containing waste water generated by the jewellery industry, and is also a cyanide-resistant strain which induces an alternative oxidase and a siderophore-based mechanism for iron acquisition in the presence of cyanide. The detection of cyanase and beta-cyanoalanine nitrilase activities in cyanide-induced cells suggests their implication in the cyanide degradation pathway.

Biodegradation, Environmental↗
PubMed1997

Geographical and seasonal association between linamarin and cyanide exposure from cassava and the upper motor neurone disease konzo in former Zaire.

High cyanide intake from consumption of insufficiently processed cassava has been advanced as a possible aetiology of the upper motor neurone disease konzo. However, similar neurodamage has not been associated with cyanide exposure from any other source. With an ecological study design, we compared 22 cases of konzo, 57 unaffected household members and 116 members from unaffected households, a total of 195 subjects, in konzo-affected savanna villages with 103 subjects in adjacent non-affected forest villages in the Paykongila area in the Bandundu Region, Zaire. In the dry season, the mean value (+/- SEM) of urinary thiocyanate, the main cyanide metabolite, was higher in the three groups in konzo-affected villages (563 +/- 105, 587 +/- 44 and 629 +/- 47 micromol/l) than in unaffected villages (241 +/- 17 micromol/l). In affected villages in the dry season when konzo incidence was high, mean urinary thiocyanate was also higher than the levels found in the wet season when incidence was low. The wet season values (mean +/- SEM) were 344 +/- 60, 381 +/- 35 and 351 +/- 27 micromol/l. Urinary levels of inorganic sulphate were low in all groups, indicating low intake of the sulphur amino-acids which provide a substrate for cyanide detoxification. These findings support an aetiological role for cyanide in konzo. However, urinary linamarin, the cyanogenic glucoside and source of cyanide in cassava, was more closely associated with the occurrence of konzo. The mean value (+/- SEM) of urinary linamarin in the konzo cases was 632 +/- 105 micromol/l and in their household members 657 +/- 52 micromol/l, which was significantly higher than in members of control households in the same village (351 +/- 28 micromol/l) and in unaffected villages (147 +/- 18 micromol/l). This suggests that a specific neurotoxic effect of linamarin, rather than the associated general cyanide exposure resulting from glucoside breakdown in the gut, may be the cause of konzo.

Adolescent↗
PubMed1995

Crystal structures of cyanide- and triiodide-bound forms of Arthromyces ramosus peroxidase at different pH values. Perturbations of active site residues and their implication in enzyme catalysis.

The structures of the cyanide and triiodide complexes of Arthromyces ramosus peroxidase (ARP) at different pH values were investigated by x-ray crystallography in order to examine the behavior of the invariant residues of arginine (Arg-52) and distal histidine (His-56) during the enzyme reaction as well as to provide the structural basis of the active site of peroxidase. The models of the cyanide complexes at pH 7.5, 5.0, and 4.0, respectively, were refined to the R-factors of 17.8, 17.8, and 18.5% using 7.0-1.6-A resolution data, and those of the triiodide complexes at pH 6.5 and 5.0 refined to 16.9 and 16.8% using 7.0-1.9-A resolution data. The structures of the cyanide complexes at pH 7.5, 5.0, and 4.0 are identical within experimental error. Cyanide ion bound to the heme in the bent conformation rather than in the tilt conformation. Upon cyanide ion binding, the N epsilon atom of His-56 moved toward the ion by rotation of the imidazole ring around the C beta-C gamma bond, but there was little conformational change in the remaining residues. The distance between the N epsilon atom of His-56 and the nitrogen atom of the cyanide suggests the presence of a hydrogen bond between them in the pH range investigated. In the triiodide complexes, one of the two triiodides bound to ARP was located at the distal side of the heme. When triiodide bound to ARP, unlike the rearrangement of the distal arginine of cytochrome c peroxidase that occurs on formation of the fluoride complex or compound I, the side chain of Arg-52 moved little. The conformation of the side chain of His-56, however, changed markedly. Conformational flexibility of His-56 appears to be a requisite for proton translocation from one oxygen atom to the other of HOO- by acid-base catalysis to produce compound I. The iron atom in each cyanide complex (low-spin ferric) is located in the heme plane, whereas in each triiodide complex (high-spin ferric) the iron atom is displaced from the plane about 0.2 A toward the proximal side.

Amino Acid Sequence↗
PubMed1998

Subunit-specific interactions of cyanide with the N-methyl-D-aspartate receptor.

Cyanide can potentiate N-methyl-D-aspartate receptor-mediated physiological responses in neurons. Here we show that this phenomenon may be attributable to a subunit-specific chemical modification of the receptor directly by the toxin. N-Methyl-D-aspartate (30 microM)-induced whole cell responses in mature (22-29 days in vitro) rat cortical neurons were potentiated nearly 2-fold by a 3-5-min treatment with 2 mM potassium cyanide, as did a similar treatment with 4 mM dithiothreitol. A 1-min incubation with the thiol oxidant 5,5'-dithiobis(2-nitrobenzoic acid) (0.5 mM) readily reversed the potentiation induced by either cyanide or dithiothreitol. Cyanide did not increase further currents previously potentiated by dithiothreitol nor was it able to potentiate responses during brief co-application with the agonist. Transient expression studies in Chinese hamster ovary cells with wild-type and mutated recombinant N-methyl-D-aspartate subunits (NR) demonstrated that cyanide selectively potentiated NR1/NR2A receptors, presumably via the chemical reduction of NR2A. In contrast, currents mediated by NR1/NR2B receptors were somewhat diminished by the metabolic inhibitor. Some of the effects of cyanide on NR1/NR2B receptors may be mediated by the formation of a thiocyanate adduct with a cysteine residue located in NR1. Cyanide thus is able to distinguish chemically between two different N-methyl-D-aspartate receptor subtypes and produce diametrically opposing functional effects.

Animals↗
PubMed2000

X-ray crystallographic study of cyanide binding provides insights into the structure-function relationship for cytochrome cd1 nitrite reductase from Paracoccus pantotrophus.

We present a 1.59-A resolution crystal structure of reduced Paracoccus pantotrophus cytochrome cd(1) with cyanide bound to the d(1) heme and His/Met coordination of the c heme. Fe-C-N bond angles are 146 degrees for the A subunit and 164 degrees for the B subunit of the dimer. The nitrogen atom of bound cyanide is within hydrogen bonding distance of His(345) and His(388) and either a water molecule in subunit A or Tyr(25) in subunit B. The ferrous heme-cyanide complex is unusually stable (K(d) approximately 10(-6) m); we propose that this reflects both the design of the specialized d(1) heme ring and a general feature of anion reductases with active site heme. Oxidation of crystals of reduced, cyanide-bound, cytochrome cd(1) results in loss of cyanide and return to the native structure with Tyr(25) as a ligand to the d(1) heme iron and switching to His/His coordination at the c-type heme. No reason for unusually weak binding of cyanide to the ferric state can be identified; rather it is argued that the protein is designed such that a chelate-based effect drives displacement by tyrosine of cyanide or a weaker ligand, like reaction product nitric oxide, from the ferric d(1) heme.

Anions↗