Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The microbiological oxidation of ferrous ion and the extraction of uranium from a low-grade ore has been studied using an adapted strain of Thiobacillus ferrooxidans. The effect of temperature, pH, volumetric oxygen transfer coefficient, K1a, and aeration number, Ia, on the activity of the microorganism has been determined. The activation energy for ferrous iron oxidation was calculated to be - 13.9 +/- 0.1 kcal/mole and inactivation (thermal death of bacteria) 53.3 +/- 0.2 kcal/mole. Temperature coefficient, Q10, was estimated to be 1.8. Uranium extraction varied between 80 and 100%.
 ...
PMID:[Ferrous ion oxidation and uranium solubilization from a lowgrade ore by "Thiobacillus ferrooxidans" (author's transl)]. 0 31

1. The thermodynamics and molecular basis of energy-linked conformational changes in the cytochrome aa3 and ATP synthetase complexes of the mitochondrial membrane have been studied with spectrophotometrical and fluorometrical techniques. 2. Ferric cytochrome aa3 exists in two conformations, high spin and low spin, the equilibrium between these states being controlled by the electrical potential difference across the mitochondrial membrane. The conformational change is brought about by an electrical field-driven binding of one proton per aa3 to the complex. At pH 7.2 the concentration of the two conformations is equal at a membrane potential of 170 mV corresponding to about 4 kcal/mole. 3. The high to low spin transition in ferric aa3 is also induced by hydrolysis of ATP in which case two molecules of aa3 are shifted per ATP molecule hydrolyzed. This is in accordance with translocation of two protons across the mitochondrial membrane coupled to hydrolysis of ATP as proposed in the chemiosmotic theory of oxidative phosphorylation. 4. The conformational transition in cytochrome aa3 is not an expression of the formation of a 'high-energy' intermediate or reversal of the energy-transducing pathway of oxidative phosphorylation, but is presumably the basis of allosteric control of the activity of cytochrome oxidase by the energy state of the mitochondrion. This control is exerted by a regulatory mechanism in which the electrical potential difference controls the conformation and redox properties of the heme centres and thereby the rate of oxygen consumption. 5. The synthesis of one molecule of ATP by oxidative phosphorylation is energetically equivalent to the work done in carrying two electrical charges across the entire mitochondrial membrane. 6. Fluorescence changes of aurovertin bound to ATP synthetase reveal that the electrical membrane potential induces a conformational change in the F1 portion of the enzyme which is probably associated with dissociation of the natural F1 inhibitor protein. This conformational change is energetically equivalent to the work done in carrying one electrical charge across the mitochondrial membrane. 7. A model is proposed for the mechanism of the electrical field-induced conformational changes in the cytochrome aa3 and ATP synthetase complexes, and the significance of these changes in the mechanism and control of mitochondrial energy conservation is discussed.
 ...
PMID:Conformational changes in cytochrome aa3 and ATP synthetase of the mitochondrial membrane and their role in mitochondrial energy transduction. 0 67

Each mole of oxyhemoglobin iron converted to methemoglobin causes the oxidation of 1.5 mol of nitrite to nitrate and consumes 1 mol of protons. No oxygen is liberated. The overall reaction has two simultaneously occurring parts. In the beginning the rate-limiting reaction converting O2Hb to metHb is directly proportional to H+ and NO2- concentrations and is independent of metHb. The second portion accounts in major part for the stoichiometry and rate of the overall reaction. In this portion O2Hb tetramers and metHbNO2- are the reactants. Essentially no reaction takes place in the presence of CN-, which displaces nitrite from the metHbNO2-, nor in the presence of 0.5 mol/liter Nal, which converts the O2Hb to alphabeta-dimers. The autocatalytic nature of the overall reaction in the presence of excess nitrite is the result of metHb, which is formed in both parts of the reaction, associating with nitrite to increase the concentration of one reactant of the cyanide-sensitive part. The reaction rates at constant pH in excess nitrite are porportional to the product of the O2Hb concentration and the square of the metHb concentration. The rate increases up to about 66% conversion of O2Hb followed by a decrease as the O2Hb becomes limiting. The dissociation constant of metHbNO2- at 25 degrees C and pH = 6.4 was found to be 1.11+/-0.11 mmol/liter.
 ...
PMID:A mechanism for the conversion of oxyhemoglobin to methemoglobin by nitrite. 1 98

Irradiation with visible light of human serum albumin in aqueous solution at pH 8, in the presence of catalytic amounts of rose bengal or methylene blue, resulted in random oxidation of the histidine residues in the protein under consumption of one mole O2, and release of somewhat less than one proton, per histidine residue degraded. An increase of light absorption at 250 nm was proportional to the amount of oxygen consumed. Bilirubin bound to the oxidized protein showed an increased light absorption at its maximum, 460 nm, and a decreased binding affinity, indicating a conformational change of the protein on oxidation of histidine residues. This change also resulted in a slight perturbation of tyrosine light absorption, corresponding to a shift of the chromophore to more polar surroundings. Further, a sensitized oligomerization of albumin was observed, independent of oxidation of the histidine residues, and not consuming oxygen. Irradiation of a complex of human serum albumin with one molecule of bound bilirubin, in the absence of a sensitizing dye, resulted in a fast, non-oxygen consuming process whereby the light absorption maximum of the pigment was shifted 4 nm towards longer wavelength and part of the bilirubin was converted to a more polar pigment, bound less firmly to the protein. This was followed by a relatively slow oxidation of the pigment under uptake of one mole O2. Parallel photooxidation of the protein carrier could not be detected. It is considered possible that the fast, anaerobic process is operative in phototherapy of hyperbilirubinemia in the newborn. Serum albumin is probably not oxidized during this treatment.
 ...
PMID:Photooxidation of human serum albumin and its complex with bilirubin. 1 94

The oxygen-binding characteristics and the multiplicity of the stripped hemoglobiin from active lungfish Protopterus amphibius, are the same as in specimens that have been estivating for about 30 months, showing that alteration in the hemoglobin molecules is not involved in the earlier reported increase in oxygen affinity of whole blood during estivation (Johansen et al., '76). At pH 7.0 and 26 degrees C the hemolysates show a high oxygen affinity (P50 = 3.1 Torr), a Bohr factor (delta log P50/delta pH) of - 0.33, and a cooperativity coefficient (n) of 1.7. Between 15 and 26 degrees C, the apparent heat of oxygenation (delta H) is - 8.6 Kcal-mole-1 at pH 7.0, corresponding with data for other fish. A low sensitivity of oxygen affinity to urea appears to be adaptive to the high urea concentrations in estivating lungfish. The salt sensitivity is, however, similar to human hemoglobin. The hemoglobin consists of two major (electrophoretically anodal) components, which differ slightly in oxygen affinity but are both sensitive to pH and nucleoside triphosphates (NTP). Guanosine triphosphate (GTP), the major erythrocytic organic phosphate, however, depresses the oxygen affinity of the composite and separated hemoglobins more effectively than ATP suggesting that GTP is the primary modulator of oxygen affinity. Comparative measurements reveal only one major hemoglobin component in P. annectens which has a markedly lower oxygen affinity and phosphate sensitivity than P. amphibius hemoglobins and thus seems less pliable to phosphate-mediated variation in oxygen affinity. The data are discussed in relation to the hemoglobin systems of other fish.
 ...
PMID:Oxygen-binding properties of hemoglobins from estivating and active African lungfish. 1 21

The enzyme preparation of L(+)-lactatoxydase (K.F. 1.1.3.2) with molecular weight of 230 000 has been isolated from the soluble fraction of the C. lipolytica cells and purified similar 360 times. The enzyme oxydizes L(+)-lactate, the optimum activity of the enzyme being observed at pH 8.0. Oxydation of the substrate is followed by accumulation of H2O2. Silver ions, p-chloromercurybenzoate and dicumarol inhibit the activity of L(+)-lactatoxydase. Iron complexones, cyanide and L-malate do not inhibit oxydation of the substrate. Pyruvate and its fluorine derivative practically do not produce any inhibiting effects either. The enzyme preparation contains 0.6 moles of flavin and 2 moles of nonhaem iron per a mole of the enzyme. Km value for the substrate is equal to 4-10(-4) M, Vmax--4.5 mkatom O/min/mg. Acidation of incubation medium leads to a decrease both of Km and Vmax. Km value for oxygen is equal to 3.1 mkM O2. Beside oxygen, ferricyanide, 2.6-dichlorphenolindophenol, phenazine methosulphate and cytochrome C may also serve as acceptors of L(+)-lactatoxydase electrons. The oxydized enzyme preparation is characterized by a spectrum absorption maximum at 410 nm. Upon L(+)-lactatoxydase reduction the maximum is shifted up to 420 nm.
 ...
PMID:[Isolation and properties of cytoplasmic L(+)-lactatoxydase of Candida lipolytica yeasts]. 1 33

A flavoprotein catalyzing the reduction of cytochrome c by NADPH was solubilized and purified from microsomes of yeast grown anaerobically. The cytochrome c reductase had an apparent molecular weight of 70,000 daltons and contained one mole each of FAD and FMN per mole of enzyme. The reductase could reduce some redox dyes as well as cytochrome c, but could not catalyze the reduction of cytochrome b5. The reductase preparation also catalyzed the oxidation of NADPH with molecular oxygen in the presence of a catalytic amount of 2-methyl-1,4-naphthoquinone (menadione). The Michaelis constants of the reductase for NADPH and cytochrome c were determined to be 32.4 and 3.4 micron M, respectively, and the optimal pH for cytochrome c reduction was 7.8 to 8.0. It was concluded that yeast NADPH-cytochrome c reductase is in many respects similar to the liver microsomal reductase which acts as an NADPH-cytochrome P-450 reductase [EC 1.6.2.4].
 ...
PMID:Studies on the microsomal electron-transport system of anaerobically grown yeast. V. Purification and characterization of NADPH-cytochrome c reductase. 1 31

Blood and tissue gas exchange properties of mole rats in normoxic and hypoxic-hypercapnic conditions were compared to the common mammalian pattern. RBC count was 14.0 +/- 1.2-10(6)/microliter. Hb concentration was 15.0 +/- 0.4g/100 ml. P50 (at pH 7.4 and 37 degrees C) was 29.5 +/- 0.5 mm Hg. Oxygen capacity averaged 20.2 +/- 0.4 vol% and the Hill coefficient was 2.9 +/- 0.1. The Bohr effect was -0.53 +/- 0.02 (deltalog P/deltapH). The temperature coefficient was 0.0152 +/- 0.0014 (deltalog P/delta degrees C). The Haldane effect was 4.8 +/- 0.5 (deltaCCO2 vol%)at PCO2 =40 mm Hg. Steady-state partial pressures in gas pockets were PO2 = 15.1 +/- 1.4 mm Hg and PCO2 = 85.8 +/- 3.9 mm Hg in normoxia, and 11.5 +/- 3.0 and 101.8 +/- 3.5 repectively in hypoxia-hypercapnia (PIO2 congruent to 85 mm Hg). Under the same conditions 2,3-DPG dropped from 0.87 and 0.88 to 0.62 and 0.65 (mol/mol Hb) in the rat and in the white rat, respectively. Heart muscle myoglobin concentration of the mole rat (1.44 mg/g) did not differ significantly from that of the white rat (1.96 mg/g), whereas masseter myoglobin was 4.0 mg/g--significantly different from the rat (1.21 mg/g). Results indicate that the strategy used by the mole rat to maintain a normal metabolic rate under variable atmospheric conditions, besides having high oxygen affinity, is to expand the physiological range of the oxygen dissociation curve to very low oxygen tensions, at the expense of its acid-base regulation. The regulation of the shape of the oxygen dissociation curve is discussed.
 ...
PMID:Blood-gas properties and function in the fossorial mole rat under normal and hypoxic-hypercapnic atmospheric conditions. 1 98

General first-order rate constants for autoxidation of sulfadiazine, sulfamerazine, sulfadimidine, sulfaperine and sulfamethoxydiazine in the air oxygen atmosphere, in solutions of pH 4-7, at 403, 411 and 418 K were determined from the absorbance measurements in 0-1 mole/dm3 HCl at 243 or 333 nm, using the so-called "subtraction technique". The thermodynamic parameters of this reaction were determined (deltaHa, deltaH not equal to, deltaS not equal to, deltaG not equal to and logA). The effect of the substituents in positions 4, 5 and 6 of the pyrimidine ring on the rate of autoxidation was interpreted in terms of the Hammett equation.
 ...
PMID:Kinetics and mechanism of degradation of some 2-sulfanilamidopyrimidine derivatives. Part III. The use of Hammett equation for kinetic investigation of 2-sulfanilamidopyrimidine derivatives autoxidation. 2 Jun 12

Yeast microbodies containing FAD-dependent alcohol oxidase, catalase and D-amino acid oxidase were isolated from methanol-grown cells of Kloeckera sp. 2201 and immobilized intact in matrices formed by a short-time illumination of photo-crosslinkable resin oligomers. The relative activities of catalase, alcohol oxidase and D-amino acid oxidase of the gel-entrapped microbodies were 36, 76 and 31% respectively as compared with those of free microbodies. Immobilization enhance d the stability of catalase to a certain degree, but not that of alcohol oxidase. The pH/activity profiles of catalase and alcohol oxidase of the entrapped organelles showed more narrow pH optima than those of the free counterparts. D-Amino acid oxidase in immobilized microbodies showed a somewhat higher Km value for D-alanine than that in free ones. Immobilized microbodies oxidized two moles of methanol to form two moles of formaldehyde with consumption of one mole of molecular oxygen. Addition of 3-amino-1,2,4-triazole, an inhibitor of catalase, reduced the formation of formaldehyde to half the amount without change in the amount of oxygen consumed, indicating the synergic action of alcohol oxidase and catalase in methanol oxidation in the microbodies of living yeast cells.
 ...
PMID:Immobilization of yeast microbodies by inclusion with photo-crosslinkable resins. 2 91


1 2 3 4 5 6 7 8 9 10 Next >>