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PubMed1978

Biological availability to the rat of intrinsic and extrinsic iron with soybean protein isolates.

Evaluations were conducted to assess the biological availability of iron in three food grade isolated soybean proteins and to evanuate the influence of these proteins on iron added to the diet from a source of known high biological availability. Ferrous sulfate was used as the standard iron source in all experiments. The biological availability was measured by a 14-day hemoglobin repletion after a 4 week depletion period using multiple dose response and comparing the test samples and standard iron source by the slope ratio assay procedure. The relative iron bioavailability for three isolated soybean proteins was A = 60%; B = 64% and C = 59% with a mean value of 61%. Autoclaving isolated soybean protein B at 108.4 degrees improved iron bioavailability over the unheated samples while isolated soybean protein A was unaffected by this treatment. Iron added to the diets containing isolated soybean protein had bioavailabilities similar to that of iron present in the soybean which supports the common dietary iron pool hypothesis. The high iron content (0.18 mg/g protein) coupled with the bioavailability data make the isolated soybean proteins a good dietary iron source.

Animals↗

PubMed2001

Experimental evidence suggesting that nitric oxide diffuses from tissue into blood but not from blood into tissue.

The aim of this study was to evaluate in vivo whether nitric oxide (NO) is able to diffuse from blood into tissues and vice versa from tissues into blood. We used an in vivo model of intestinal ischemia (superior mesenteric artery occlusion) selectively increasing NO levels in intestinal tissue and an infusion of L-arginine selectively increasing NO levels in blood. In this model we followed formation of nitrosyl complexes of hemoglobin (Hb-NO) in blood and nitrosyl-diethyldithiocarbamate-iron complexes (DETC--Fe--NO) in ischemic intestine and normoxic tissues by means of electron paramagnetic resonance spectroscopy. NO trapping by DETC--Fe in the tissues resulted in a reduction of Hb--NO levels in blood accompanied by the formation of water-insoluble DETC--Fe-NO complexes in ischemic intestine and normoxic tissues both during ischemia and during reperfusion. Administration of L-arginine increased NO levels in blood but neither in ischemic intestine nor in normoxic tissue. Our data suggest that NO released in blood from endothelial cells does not diffuse into tissue. In contrast, NO formed in tissue diffuses into blood. The latter indicates that NO formed in tissues may exert its biological activities systematically.

Animals↗

PubMed1992

Purification and characterization of liposomes encapsulating hemoglobin as potential blood substitutes.

In view of the desirability to increase the survival time of the liposome-based artificial red blood cells in vivo, the variables influencing optimum hemoglobin capture and preservation for the bovine hemoglobin-loaded liposomes (LEHb) are investigated. In order to predict the in vivo response, the necessary experiments for the in vitro system characterization have been carried out. The liposomes are prepared by the Reverse Phase Evaporation technique and then purified using a Sepharose 4B column. The purified LEHbs display a unimodal size distribution in the submicron range with a volume average diameter of 0.115 microns and a particle count of 1.25* 10(15) per ml of suspension. Analysis of the lipi/Hb content of the liposomes reveals that the variations in the ratio of Hb encapsulated to lipid entrapped (Hb/L)f as a function of the initial Hb concentration ([Hb]o) is insignificant compared to the net augmentation of (Hb/L)f as a function of the increasing initial lipid to Hb loading ([L]o). Meanwhile high [Hb]o s are necessary for the preservation of oxyhemoglobin.

Animals↗

PubMed2006

NO* release from MbFe(II)NO and HbFe(II)NO after oxidation by peroxynitrite.

In this work, we showed that the reaction of peroxynitrite with MbFe(II)NO, in analogy to the corresponding reaction with HbFe(II)NO (Herold, S. Inorg. Chem. 2004, 43, 3783-3785), proceeds in two steps via the formation of MbFe(III)NO, from which NO* dissociates to produce iron(III)myoglobin (Mb = myoglobin; Hb = hemoglobin). The second-order rate constants for the first steps are on the order of 10(4) and 10(3) M(-1) s(-1), for the reaction of peroxynitrite with MbFe(II)NO and HbFe(II)NO, respectively. For both proteins, we found that the values of the second-order rate constants increase with decreasing pH, an observation that suggests that HOONO is the species responsible for oxidation of the iron center. Nevertheless, it cannot be excluded that the pH-dependence arises from different conformations taken up by the proteins at different pH values. In the presence of 1.2 mM CO2, the values of the second-order rate constants are larger, on the order of 10(5) and 10(4) M(-1) s(-1), for the reaction of peroxynitrite with MbFe(II)NO and HbFe(II)NO, respectively. The pH-dependence of the values for the reaction with MbFe(II)NO suggests that ONOOCO2- or the radicals produced from its decay (CO3*-/NO2*) are responsible for the oxidation of MbFe(II)NO to MbFe(III)NO. In the presence of large amounts of nitrite (in the tens and hundreds of millimoles range), we observed a slight acceleration of the rate of oxidation of HbFe(II)NO by peroxynitrite. A catalytic rate constant of 40 +/- 2 M(-1) s(-1) was determined at pH 7.0. Preliminary studies of the reaction between nitrite and HbFe(II)NO showed that this compound also can oxidize the iron center, albeit at a significantly slower rate. At pH 7.0, we obtained an approximate second-order rate constant of 3 x 10(-3) M(-1) s(-1).

Carbon Dioxide↗

PubMed1986

Oxygen equilibrium study and light absorption spectra of Ni(II)-Fe(II) hybrid hemoglobins.

Ni(II)-Fe(II) hybrid hemoglobins, in which hemes in either the alpha or beta subunit are substituted with Ni(II) protoporphyrin IX, have been prepared and characterized. Since Ni(II) protoporphyrin IX binds neither oxygen nor carbon monoxide, the oxygen equilibrium properties of the Fe subunit in these hybrid hemoglobins were specifically determined. K1 values, namely the equilibrium constants for the first oxygen molecule to bind to hemoglobin, agreed well for these hybrid hemoglobins with the K1 value of native hemoglobin A in various conditions. Therefore, Ni(II) protoporphyrin IX in these hybrid hemoglobins behaves like a permanently deoxygenated heme. Both Ne-Fe hybrid hemoglobins bound oxygen non-co-operatively at low pH values. When the pH was raised, alpha 2 (Fe) beta 2 (Ni) showed co-operativity, but the complementary hybrid, alpha 2 (Ni) beta 2 (Fe), did not show co-operativity even at pH 8.5. The light absorption spectra of Ni(II)-Fe(II) hybrid hemoglobins indicated that the coordination states of Ni(II) protoporphyrin IX in the alpha subunits responded to the structure of the hybrid, whereas those in the beta subunits were hardly changed. In a deoxy-like structure (the structure that looks like that observed in deoxyhemoglobin), four-co-ordinated Ni(II) protoporphyrin IX was dominant in the alpha (Ni) subunits, while under the conditions that stabilized an oxy-like structure (the structure that looks like that observed in oxyhemoglobin), five-co-ordinated Ni(II) protoporphyrin IX increased. The small change observed in the absorption spectrum of the beta (Ni) subunits is not related to the change of the co-ordination number of Ni(II) protoporphyrin IX. Non-co-operative binding of oxygen to the beta subunits in alpha 2 (Ni) beta 2 (Fe) accompanied the change of absorption spectrum in the alpha (Ni) subunits. We propose a possible interpretation of this unique feature.

Ferrous Compounds↗

PubMed1989

The effect of iron therapy on malarial infection in Papua New Guinean schoolchildren.

The effect of iron therapy on malarial infection was investigated in Papua New Guinea, where malaria is endemic. Prepubescent schoolchildren with hemoglobin levels of 8-12 g/dl were randomly assigned to receive either 200 mg ferrous sulfate or a placebo twice daily for 16 weeks. Iron status and malarial infection were assessed at baseline, after 6 and 16 weeks of therapy, and 8 weeks after therapy was discontinued. Iron status was significantly improved by the treatment. The treatment did not significantly affect parasite rate, parasite density, or levels of anti-malarial IgG. No changes in spleen size were observed in either group. Furthermore, there was no significant difference between the groups in reported episodes of suspected malaria during the therapy. These results suggest that, in malaria endemic areas, oral treatment for iron deficiency can be carried out in semi-immune or immune schoolchildren without adverse consequences.

Anemia, Hypochromic↗

PubMed1993

A nonlinear dosimetric model for hemoglobin adduct formation by the neurotoxic agent acrylamide and its genotoxic metabolite glycidamide.

Hemoglobin (Hb) adducts, formed by the neurotoxic agent acrylamide (AA) and its genotoxic metabolite glycidamide (GA), were measured in the rat by means of a method for simultaneous determination of the adducts formed to cysteine. A novel, nonlinear dosimetric model was developed to describe Hb adduct formation. This model incorporates the saturable kinetics of the metabolic conversion in vivo of AA to GA. The pharmacokinetic parameters Vmax and Km and the first-order rates of elimination, k1 and k2, for AA and GA from all processes except conversion of AA to GA, were estimated directly from Hb adduct data to 19 M hr-1, 66 microM, 0.21 hr-1, and 0.48 hr-1, respectively. At low concentrations, approximately 60% of AA was metabolized to GA. The nonlinear dosimetric model for adduct formation has potential general applicability in high-to-low-dose extrapolation of genotoxic effects.

Acrylamide↗

PubMed1991

Hemoglobin adducts and urinary mercapturic acids in rats as biological indicators of butadiene exposure.

Binding of 1,2-epoxy-3-butene, the primary metabolite of butadiene, to hemoglobin (Hb) and excretion of its mercapturic acid in urine were studied as potential indicators of butadiene exposure. Four groups of Wistar rats were exposed to butadiene at 0, 250, 500 and 1000 ppm 6 h/day, 5 days/week, during 2 weeks. Blood was collected at the end of exposure and 17 days later for analysis of hemoglobin adducts and adduct stability. Urine was collected each day during exposure (afternoon samples) and in between exposures (morning samples). Adducts of 1,2-epoxy-3-butene to N-terminal valine in Hb were measured using the N-alkyl Edman procedure and GC/MS of the thiohydantoin derivatives. The corresponding mercapturic acid was analysed, after deacetylation, through derivatization with phthaldialdehyde and HPLC with fluorescence detection. The Hb adducts proved to be stable and are therefore useful for dosimetry of long-term exposure to butadiene. The adduct levels increased linearly with exposure dose up to 1000 ppm (3 nmol/g Hb at 1000 ppm). The increase with exposure dose of the mercapturic acid concentration in urine was also compatible with a linear dose response up to 1000 ppm. The sensitivity of both analytical methods needs to be improved for their application to human samples.

Acetylcysteine↗

PubMed2004

Iron absorption from NaFeEDTA is downregulated in iron-loaded rats.

NaFeEDTA is a promising fortificant for use in plant foods, because it is less susceptible to iron absorption inhibitors and has fewer undesirable impacts on sensory quality than ferrous sulfate. However, the hypothesis that iron absorption from NaFeEDTA is effectively downregulated in iron-overload conditions has not been thoroughly tested. Therefore, the objective of this study was to compare downregulation of iron absorption from ferrous sulfate and NaFeEDTA in intact iron-loaded rats. Male Sprague-Dawley rats were fed diets containing either ferrous sulfate (35 mg Fe per 1 kg diet) or elemental iron (30,000 mg Fe per 1 kg diet) for 29 d to achieve basal or iron-loaded status. While body weights and hemoglobin concentrations were the same for basal and iron-loaded rats, nonheme-iron concentrations in liver, spleen, and kidney were all significantly higher in iron-loaded rats, indicating elevated iron status. Percentage of iron absorption from (59)Fe-labeled ferrous sulfate and NaFeEDTA, determined from whole-body retention of (59)Fe activity, was 64.7 and 49.4% in basal rats but decreased to 12.8 and 10.2% in iron-loaded rats, respectively. The reductions in percentage of iron absorption from both iron sources in rats as a result of iron loading were comparable (about -80% for both iron sources). Our results suggest that iron absorption from NaFeEDTA and ferrous sulfate is downregulated to a similar extent in iron-loaded rats. Hence, NaFeEDTA is no more likely than ferrous sulfate to exacerbate iron overload in subjects with adequate body iron stores.

Absorption↗

PubMed1985

Nature of the FeO2 bonding in myoglobin: an overview from physical to clinical biochemistry.

The iron(II)-dioxygen bond in myoglobin and hemoglobin is a subject of wide interest. Studies range from examinations of physical-chemical properties dependent on electronic structure, to investigations of stability as a function of oxygen supply. Stability properties are of particular importance in vivo, since the oxygenated form is known to be oxidized easily to the ferric form, which cannot be oxygenated and is therefore physiologically inactive. Kinetic and thermodynamic studies of the stability of native oxymyoglobin have revealed a new feature in FeO2 bonding. In vivo, the iron center is always subject to a nucleophilic attack of the water molecule or hydroxyl ion, which can enter the heme pocket from the surrounding solvent, and thereby irreversibly displace the bound dioxygen from MbO2 in the form of O2- so that the iron is converted to the ferric form. A free energy diagram for the potential reactions of FeO2 visualizes myoglobin as a molecular structure that can provide in solution the delicate balance of kinetic and thermodynamic factors necessary to stabilize reversible oxygenation, as opposed to irreversible autoxidation to metmyoglobin.

Animals↗

PubMed1994

High-pressure flash photolysis study of hemoprotein: effects of substrate analogues on the recombination of carbon monoxide to cytochrome P450CAM.

The effects of camphor and camphor analogues on the CO recombination kinetics of ferrous cytochrome P450CAM (P450CAM) at 293 K have been studied as a function of hydrostatic pressure (0.1-200 MPa) by means of flash photolysis. At 0.1 MPa, the association rate constant (kon) for substrate-free P450CAM is 8.5 x 10(6) M-1 s-1. Measurements as a function of pressure lead to a determination of the activation volume (delta V not equal to) of +4 cm3 mol-1 for substrate-free protein. This positive delta V not equal to is interesting because the CO association reaction of various hemoproteins, such as myoglobin and hemoglobin, exhibit negative delta V not equal to values [Adachi, S., & Morishima, I. (1989) J. Biol. Chem. 264, 18896-18901; Unno, M., Ishimori, K., & Morishima, I. (1990) Biochemistry 29, 10199-10205]. The binding of d-camphor and some camphor analogues (d-fenchone, 3-endo-bromocamphor, and 3,3,5,5-tetramethylcyclohexanone) into the heme pocket strongly influences the kinetics, i.e., kon is reduced ((1-10) x 10(5) M-1 s-1) and delta V not equal to is altered to a negative value (-14 to -32 cm3 mol-1). The negative delta V not equal to suggests that the effects of camphor and these camphor analogues are due to an increase in the iron-ligand bond formation barrier. On the other hand, the binding of adamantane and norcamphor does not affect the kinetics. This result is particularly surprising because both substrate analogues are located in the immediate vicinity of the CO binding site.(ABSTRACT TRUNCATED AT 250 WORDS)

Camphor↗

PubMed2003

Effects of iron(II) salts and iron(III) complexes on trace element status in children with iron-deficiency anemia.

Iron-deficiency anemia (IDA) is the most common nutritional deficiency in childhood throughout the world. Although it has been shown that IRA is associated with elevated plasma copper and depleted zinc levels in children, there are conflicting results on the effect of iron supplementation on the absorption of these elements. The aim of this study was to investigate the effects of ferrous and ferric iron supplementation on the trace element status in children (n=25, aged 8-168 mo) with IDA. Fourteen of them were treated with ferric hydroxide-polymaltose complex (Ferrum, Vifor, Switzerland) (6 mg/d in the first 3 mo for initial therapy and 3 mg/kg for 3 mo as maintenance); the others were treated with a ferrous sulfate complex (FerroSanol, Schwarz, Germany) (6 mg/d in the first 3 mo for initial therapy and 3 mg/kg for 3 mo as maintenance). Plasma copper, zinc, and ceruloplasmin levels as well as hematological parameters were determined at baseline and the first, third, and sixth month of the treatment period. The hemoglobin and iron levels of patients in both groups were higher in the first and sixth months compared to baseline. Although the ceruloplasmin levels were depleted (48.9 mg/dL vs 41.4 mg/dL, p=0.035) during ferrous iron treatment, the copper and zinc levels remained unchanged. On the other hand, ferric iron supplementation led to an increase in zinc levels in the sixth month of treatment (0.77 mg/L vs 1.0 mg/L, p=0.021). The plasma copper levels were lower in the ferrous iron-treated group at the end of the first month of treatment than in the ferric irontreated group (1.06 mg/L vs 1.29 mg/L, p=0.008). In conclusion, our data showed that copper and ceruloplasmin metabolisms were affected by ferrous iron supplementation, whereas ferric iron kept them to normal levels of zinc, possibly by affecting their absorption. We conclude that the copper and zinc status of patients with IDA should be taken into consideration before and after iron therapy.

Adolescent↗

PubMed1993

Liposome-encapsulated hemoglobin using film hydration processing to form artificial red blood cells.

Process parameters using a Microfluidizer M110 to produce liposome-encapsulated hemoglobin (LEH) were further studied to examine their effect on hemoglobin (Hb) encapsulation efficiency (yield), steady shear viscosity, mechanical stability, and oxygen delivery. Liposome formulation loading ratios of up to 300 mumol of lipid per ml of Hb solution were evaluated; a maximum yield was obtained at 300 mumol/ml. Liposomes containing encapsulated Hb concentrations as high as 15.5 g/100 ml were prepared. LEH particle size distribution, determined from negatively stained whole mount preparations using transmission electron microscopy, resulted in average vesicle sizes for optimal batches of about 155 nm. Steady shear viscosity of LEH (up to 40% by volume) in an isotonic-isooncotic solution of PBS containing either albumin or dextran were evaluated for shear rates to 2000 s-1. Values obtained were generally higher than those of whole blood at all shear rates tested. Little leakage of Hb from liposomes stored in isotonic PBS was observed as a function of storage time and shear rate. Administration of LEH supported life in rats whose hematocrit had been reduced via isovolemic exchange transfusion to levels well below 5%, which was incompatible with survival when exchange transfusion was performed with the isotonic-isooncotic PBS solution.

Animals↗

PubMed1993

Erythropoietin increases hemoglobin in cancer patients during radiation therapy.

PURPOSE: The hemoglobin (Hgb) level of patients during radiation therapy is associated with both survival and local tumor control in several organ sites. This clinical trial tested whether administering recombinant human erythropoietin (r-HuEPO) to cancer patients would increase their Hgb level during the course of radiation therapy without adverse effects. METHODS AND MATERIALS: The 40 participating patients had a Hgb value < 13.5 g/dL and a malignant tumor located above the diaphragm without evidence of distant metastasis for which they were scheduled to undergo a 5-8 week course of daily radiation therapy. All 40 patients were given oral ferrous sulfate throughout their radiation therapy course. Half the patients also received 150-300 mg/kg of r-HuEPO subcutaneously three times per week starting 0-10 days prior to the first dose of radiation. RESULTS: The r-HuEPO and control groups did not differ significantly in patient age, gender, tumor type, initial hemoglobin, erythropoietin, or iron bioavailability. The Hgb level increased more than 6% during radiation therapy in all 20 of the r-HuEPO patients but in only 2/20 of the control patients (p < 0.001). The Hgb rose from a mean +/- standard deviation of 11.9 +/- 1.3 g/dL to > 14 g/dL during radiation therapy in 80% of the r-HuEPO group compared to in 5% of the control group (p < 0.001). The mean +/- s.d. change in Hgb concentration during radiation therapy was 27 +/- 15% (an average rise of 5% per week) in the r-HuEPO group and 0 +/- 6% in the control group (p < 0.001). r-HuEPO had no significant measurable effect on blood pressure, white blood cell, neutrophil or platelet count, or liver or renal function. The only reported adverse effect of r-HuEPO administration was an asymptomatic skin rash in one patient. CONCLUSION: r-HuEPO with ferrous sulfate significantly increased the Hgb level in cancer patients without interfering with their course of radiation therapy, whereas ferrous sulfate alone did not. r-HuEPO appears to be a safe and effective means of increasing red cell mass during radiation therapy.

Erythropoietin↗

PubMed1997

Stereochemistry of the Fe(II)- and Fe(III)-cyanide complexes of the homodimeric Scapharca inaequivalvis hemoglobin. A resonance Raman and FTIR study.

Resonance Raman measurements carried out in parallel on ferrous and ferric Scapharca inaequivalvis dimeric hemoglobin cyanide derivatives allowed the identification of the electron density marker bands and heme core size marker bands in both derivatives in comparison with those obtained for the carbonmonoxy and deoxy adducts. The iron cyanide stretching mode, measured for the first time in a ferrous hemoprotein, has been detected at 455 cm(-1), only 6 cm(-1) lower than in the corresponding ferric derivative. This finding demonstrates that the large free energy difference for complex formation between the two derivatives is not concentrated on the Fe-C bond. The internal stretching frequencies of the ligand in the ferric and ferrous derivatives have been identified by FTIR and Raman measurements using different cyanide isotopes. The frequency decreases in the order Fe(III)-CN adduct, free cyanide, Fe(II)-CN adduct, consistent with the behavior observed in inorganic complexes and horseradish peroxidase. The main feature emerging from these data is that cyanide, at variance with oxygen and carbon monoxide, binds to ferrous iron with only a minor perturbation of the electronic structure of the heme. The functional counterpart of this effect is the absence of cooperative cyanide binding in HbI.

Animals↗

PubMed1995

Effect and safety of liposome-encapsulated hemoglobin neo red cells (NRCs) as a perfusate for total cardiopulmonary bypass.

We developed a liposome encapsulated hemoglobin named Neo Red Cells (NRC), NRC (1) readily circulates, (2) shows a high oxygen transport efficiency, and (3) has a strong capsule membrane. In this study, we evaluated the effect of NRC as a priming solution for total cardiopulmonary bypass (TCPB) using a dog. The TCPB was started after removal of 57.1-73.3% of autologous blood and continued for 7 hours. During TCPB using NRC, the vascular resistance (VR) decreased to 1/4 of VR when red blood cells (RBC) were used. This change suggests that NRC, the viscosity of which is lower than that of RBC, reduced the load on the circulation system. The oxygen volume delivered by NRC was higher than that delivered by RBC, resulting in a greater oxygen consumption with NRC. During TCPB using NRC, the serum LDH level was lower than that using RBC. So we concluded that NRC compensated for the reduction in the oxygen transport ability, which is a disadvantage of dilution TCPB, and further increased the circulation improving effect and anti-hemolytic effect, which are advantages of the procedure. It, thus, enhanced both the safety and effectiveness of dilution TCPB.

Animals↗

PubMed1985

Lack of adverse side effects of oral ferrous sulfate therapy in 1-year-old infants.

An evaluation was made of 278 healthy-appearing 1-year-old infants who were tested for iron deficiency to determine the relative frequency of adverse side effects attributable to oral iron treatment. After obtaining parental informed consent, laboratory tests of iron status were performed on venous blood and infants with hemoglobin level greater than 10.5 g/dL were randomly chosen to receive 1.2 mL of ferrous sulfate (FeSO4) drops (about 3 mg of iron per kilogram per day) or equal volume of placebo for 3 months. After 3 months of treatment, infants were to return to the clinic for repeat blood testing, compliance estimation, and evaluation for possible adverse side effects. There was no significant difference (P greater than .50) in the frequency of vomiting, diarrhea, or fussiness in iron-treated infants (6%) compared with placebo-treated infants (9%). Constipation was slightly more frequently reported (P = .03) in placebo-treated infants (9%) than in iron-treated infants (1%). Compliance with therapy was confirmed in 179 completely evaluated infants by the lack of remaining medication at 3 months, the higher incidence (P less than .0001) of dark stools reported among iron-treated infants, and the changes in laboratory tests of iron status. No parents reported dark stools as an adverse effect of therapy. It is concluded that once daily, moderate-dose FeSO4 therapy given to fasting 1-year-old infants results in no more gastrointestinal side effects than placebo therapy.

Administration, Oral↗

PubMed1997

Dynamics of cyanide binding to ferrous Scapharca inaequivalvis homodimeric hemoglobin.

Flash photolysis experiments have been carried out for the first time on a hemoglobin ferrous cyanide adduct with an 8 ns laser pulse. A 95% nonexponential rebinding process occurs within 2 micros after full photolysis in ferrous cyanide dimeric Scapharca inaequivalvis hemoglobin (HbI), indicating that once photolyzed the cyanide anion is not able to escape from the protein matrix and rebinds to the heme iron. The resonance Raman spectrum of the 10 ns photoproduct is identical to that of the fully relaxed deoxy derivative, indicating that in the ferrous cyanide HbI adduct protein relaxation occurs within 10 ns after photolysis. This behavior is at variance with that of the carbonmonoxy HbI derivative in which very little geminate rebinding is observed and the photoproduct relaxes with a lifetime of 1 micros. The fast relaxation of the cyanide HbI photoproduct can be accounted for by the small perturbation of the heme structure induced by cyanide binding to ferrous HbI. This is consistent with a deoxy-like conformation of the HbI ferrous cyanide adduct and implies that the pathway for relaxation involves only minor local rearrangements of the heme moiety. Photolysis experiments carried out on ferrous cyanide horse myoglobin, which can be saturated only partially, show a qualitatively similar behavior in ligand rebinding, indicating that the geminate process of the cyanide anion is a general phenomenon in hemoproteins.

Animals↗