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Query: UNIPROT:Q0Z944 (hemoglobin)
 63,986 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The Haldane coefficient (the amount of the oxygen-linked hydrogen ion binding of hemoglobin) was determined in bovine erythrolysate (Hb concentration equals 13.5 mM) by means of the differential titration method with varying PCO2 from 0 to 74 mm Hg and pH from 6.0 to 8.5 at 37 degrees C. The maximum value of the coefficient was found to be 0.49 mM per mM Hb at PCO2 equals 0 and pH 7.20. With increasing of PCO2, the coefficient became smaller in all ranges of pH studied. The coefficient under the conditions of pH 7.20 and PCO2 equals 45 mm Hg that are normally prevailing in the interior of bovine erythrocytes was 0.31.
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PMID:The oxygen-linked hydrogen ion binding (the Haldane coefficient) of bovine hemoglobin. 1 Nov 19

The arterial (a), mixed venous (v), and arterial-mixed venous differences (A-V) of hydrogen ion concentration ([H+]), PCO2, HCO-3 and base excess (BE) were measured during 3 h in control (C), water-depleted (WD) and water- and salt-depleted (WSD) dogs. In WD animals the difference in hydrogen ion concentration between venous and arterial blood increased because the [H+] increased more in venous than in arterial blood. In WSD animals (A-V) [H+] remained unchanged since both [H+]a and [H+]v increases were parallel. [H+] variations seem to represent the changes in fixed-acid concentration of blood. The difference between both groups of animals in (A-V) [H+] changes could be ascribed to PCO2 variations. [HCO-3] values changed inconsistently. Arterial samples from the experimental groups showed a continuous decrease at the same rate of change. The mean values in WSD were lower than in WD. [HCO-3]v of WSD decreased slowly during the experiment. The rate of decrease of (A-V) [HCO-3] was higher in WD than in WSD. The different behavior of of [HCO-3] between both arterial and mixed venous samples and among experimental groups disappeared if [HCO-3] changes were corrected for bicarbonate generation due to PCO2 variation (respiratory bicarbonate). Thus [HCO-3] corrected for PCO2 variation represents metabolic changes, in good agreement with both [H+] and BE variations. The metabolic acidosis cannot be explained only on the basis of the increase in blood lactate; it is suggested that other fixed acids might contribute to the decrease in blood bicarbonate. In both experimental groups PvCO2 increased continuously. The (A-V) PCO2 showed the same rate of change. There is a good relationship between this increase and the degree of plasma volume change. It therefore might be that PvCO2 increase is a direct consequence of hemodynamic impairment. In WD and WSD, BE decreased progressively in both arterial and mixed venous samples. BEa values were lower than BEv values after the experiment began. (A-V) BE decreased in an exponential manner in both experimental groups; this change could be ascribed to the increased level of deoxygenated hemoglobin in mixed venous blood, thus giving rise to a decrease in fixed acid concentration.
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PMID:Arterial and mixed venous PCO2 and hydrogen ion, bicarbonate and base excess concentrations in water-depleted dogs. 1 42

A mass spectrometric method was developed to determine pH-dependent hydrogen-deuterium exchange at the C-2 position of the imidazole ring of histidine, after converting the amino acid to the methylthiohydantoin derivative. The amount of deuterium exchange in N-acetyl-histidine estimated by the present method was confirmed to be in good agreement with that determined by NMR spectrometry. N-Acetylhistidine was deuterated at various pH's. From the amount of deuterium exchange, a pseudo-first order rate constant (kpsi) was calculated. A pKa value of 7.2 for the amino acid was obtained from the relation between kpsi and pH. This method was applied to estimate the pKa value of beta-146 histidine in human hemoglobin. Human hemoglobin deuterated at various pH's was digested with carboxypeptidase A [EC 3.4.12.2] to release the beta-146 histidine. The amount of deuterium exchange in the isolated histidine was determined to obtain kpsi. From these measurements pKa values of 7.0 for the histidine in oxyhemoglobin and of 8.2 for that in deoxyhemoglobin were found at 36.5 degrees, respectively.
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PMID:Studies on the heterotropic interaction of hemoglobin. I. Mass spectrometric method for determination of the pKa of the beta-146 histidine residue in human hemoglobin. 1 48

Over a century ago, Stokes wrote on the oxidation and reduction of "the colouring substance of the blood." The mechanisms that govern the binding of oxygen to hemoglobin have been defined in even greater detail and higher orders of accuracy, even to the ends of the oxyhemoglobin dissociation curve. The Bohr effect has ceased to be a reduction in the affinity of hemoglobin for oxygen due to an increasing hydrogen ion concentration and according to a mere logarithmic equilibration constant. The constant has become a variable, subject to the interactions of temperature, carbon dioxide, organic phosphate, and ionic concentrations. This interdependence of so many variables has rendered the once inaccurate, but precise prediction of the effect of tht, well beyond the means of the average physician managing the treatment of a sick patient.
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PMID:"The colouring substance of blood.". 3 52

Studies were carried out on fresh cord blood obtained at delivery from nonstressed normal fetuses ranging from 24 to 42 weeks of gestation, to determine the relationship of 2,3-diphosphoglycerate (DPG), the intracellular red cell and extracellular pH, and the proportions of adult and fetal hemoglobin in regulating the position of fetal red cell oxygen affinity in utero. There was a significant positive correlation between P50 and gestational age (r = .62, P less than .001), the linear regression increased from 17.8 to 22.5 mm Hg. There was also a significant positive correlation between P50 and the percentage of adult type hemoglobin (HbA) (r = .67, P less than .001). In contrast gestational age had no effect of 2,3-DPG levels, the mean and SD was 14.86 +/- 2.04 mol/gm of Hb or delta pH between plasma and red cell, the mean was 0.187 +/- SD 0.032. However, there was a significant negative correlation between the intraerythrocyte hydrogen ion concentration and DPG level (r = .5, P less than .025). It is concluded therefore that the decrease in fetal oxygen affinity as gestation progresses is related mainly to the increase in the amount of HbA and the levels of DPG or delta pH between plasma and red cells are not a function of gestational age.
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PMID:Red cell oxygen affinity, hemoglobin type, 2,3-diphosphoglycerate, and pH as a function of fetal development. 4 Jan 81

C3, GBG, and orosomucoid polymorphisms were electrophoresed in a high-voltage agarose method which permitted the typing of 15-20 samples. The increased sensitivity of the dye Coommassie blue was used to stain the protein, and yielded higher resolution than amido black. The typing of haptoglobin samples, was facilitated by devising a method which utilizes the peroxidase activity of the haptoglobin-hemoglobin complex with 90-tolidine and hydrogen peroxide as substrates and 4-chloro-1-naphthol as coupler.
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PMID:C3, GBG, orosomucoid and haptoglobin polymorphisms. Improved staining methods. 4 56

An alkaline diaminobenzidine (DAB) medium has been used to identify peroxidase activity in small granules (0.09 to 0.2 mu in diameter) present in all forms of maturing erythrocytic cells with the exception of erythrocytes. These granules, which were more frequent in proerythroblasts (from two to seven by thin section), were distinct from pleomorphic granules present in the close proximity to the Golgi apparatus. They were also distinct from ferritin molecules which were seen as aggregates in siderosomes of polychromatophilic erythroblasts. They often appeared in close association with the smooth membrane of the nuclear envelope. Optimal conditions for the visualization of these granules by incubation in alkaline DAB were obtained when the peroxidase activity of hemoglobin was reduced by addition of low concentrations of potassium cyanide. Lack of hydrogen peroxide in the incubation media completely inhibited the staining reaction of hemoglobin, while the positive reaction persisted in the granules. Aminotriazole in the incubation media prevented the staining of these organelles. These findings suggest that small granules seen in maturing erythroblasts contain catalase and that they correspond to microperoxisomes described in other tissues. The mechanism of their disappearance during reticulocyte maturation is unknown. The relationship between particulate catalase of erythroblasts and soluble erythrocytic catalase has not been elucidated.
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PMID:Fine structural and cytochemical identification of microperoxisomes in developing human erythrocytic cells. 4 50

A selective staining of hemoglobin in erythroid cell series was achieved by use of Sudan Black B (modified method of Sheehan and Storey) if optimal amount of hydrogen peroxide was added to the staining mixture. The effect of some inhibitory agents (KCN, wet heat, pH) on this staining as well as on the Lepehne's pseudoperoxidase reaction for hemoglobin was similar. Both reactions were more resistant to these factors than the peroxidase reactions and sudanophilia in granulocytes in which both could be blocked by the pretreatment with absolute methanol. Moreover the effect of some extraction procedures for lipids on both myeloperoxidase reactions and sudanophilia was investigated. The results support the view that the sudanophilia in granulocytes is due to their peroxidase activity and for the staining of hemoglobin by use of Sudan Black B with H2O2 its pseudoperoxidase activity is responsible. In addition the effect of the substitution of phenolphosphate by dihydroxybenzenes on granulocyte sudanophilia is reported.
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PMID:Peroxidase and pseudoperoxidase reactions in relation to sudanophilia. 7 Dec 89

The effects of ionic strength, urea, calcium and fluorine ions, ouabain and cholinesterase inhibitors on the changes in the ionization equilibrium of an erythrocyte suspension under heating were studied. Proton release by erythrocytes was compared to a release of potassium ions and hemoglobin from the cells. The proton release under heating is mainly determined by the physico--chemical properties of superficial structures of erythrocytes and does not depend on the activity of cholinesterase, ATPase and glycolytic processes.
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PMID:[Changes in the ionization equilibrium of erythrocyte suspension under heating]. 13 48

Menadione in the presence of oxyhemoglobin will accelerate the formation of methemoglobin and result in the generation of superoxide anion. Menadione appears to oxidize slowly ferrohemoglobin to ferrihemoglobin, while forming menadione semiquinone in the process. Menadione semiquinone is known to react with molecular oxygen to yield superoxide anion. The superoxide anion appears to be the source of hydrogen peroxide which accounts for most of the observed methemoglobin formation when hemoglobin is reacted with menadione.
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PMID:Production of superoxide anion during the oxidation of hemoglobin by menadione. 18 30


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