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Query: UNIPROT:P06889 (Mol)
 630,302 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Influence of pH was studied on the absorption spectra (340-670 nm) and on the curves of abnormal dispersion of optic rotation (220-270 nm) of the lupine ferri-leg-hemoglobin (Lb). pH range of the existence of the lupine Lb native form was determined (pH 5.5-11.0 at 20-25degrees C). It has been shown that not only met-hydroxy transition (which is in a complicated manner connected with the ionization of both ligand-bound water and certain amino acid residues of globin) but the ionization of a group with pK approximately 5, too, in the native molecule produces a heterotropic effect onto the haem. Complex analysis of the acidic and alkaline denaturation evidences that these processes are cooperative and proceed via several stages. pK values and the number of tyrosine residues were determined; it has been shown that these amino acid moieties are "buried" in the protein molecule. The results are discussed on the basis of a tentative model of the lupine Lb spatial suggested by the authors.
Mol Biol (Mosk)
PMID:[Acid-alkaline equilibrium of the ferri-leg-hemoglobin of the lupine (Lupinus luteus L.) Spectral studies]. 0 59

1. Angiotensin has previously been shown to inhibit distal renal tubular sodium reabsorption. As a consequence of this, or independently, it might influence the distal handling of other electrolytes. We have therefore examined the effects of angiotensin on the distal reabsorption or secretion of a spectrum of electrolytes. 2. Standard bilateral stop-flow studies were done on anaesthetized, adrenalectomized rabbits, in which the effects of intravenous infusions of either 0-02-0-05 mug min-1 kg-1 or 1 mug min-1 kg-1 of angiotensin were compared with control stop-flow results. 3. The lower dose of angiotensin inhibited distal sodium, chloride, water and magnesium reabsorption, inhibited distal hydrogen secretion and stimulated distal potassium secretion. The higher dose of angiotensin produced these changes and additionally inhibited distal calcium reabsorption. Most of the observed changes were dose-related. The low dose of angiotensin did not significantly raise blood pressure but the high dose was pressor. 4. Changes in the stop-flow patterns induced by the higher dose of angiotensin were compatible with, and may help to explain, the changes it produced in urinary excretion of sodium, chloride, potassium, magnesium and calcium in clearance studies before stop-flow. Suppression of hydrogen secretion caused by both doses of angiotensin in the stop-flow studies was also reflected by reductions in acid excretion produced by these infusion rates in additional experiments performed by clearance methods in acid-loaded, conscious rabbits. 5. The results support the view that angiotensin may have an important intrarenal role, at least in rabbits.
Clin Sci Mol Med 1976 Feb
PMID:Multiple changes in distal stop-flow electrolyte patterns and reduction of acid excretion induced in rabbits by angiotensin. 0 4

The pH-dependence of the 3H to 1H exchange between water and C(8)H groups of purine, adenine, 9-methyladenine, 7-methyladenine, hypoxanthine, guanine, xanthine as well as C(2)H groups of imidazole and benzimidazole was studied. It was shown that within the pH-ranges, where the majority of molecules under study are non-ionized, the values of observed rate constant (kobs) do not depend on pH. Beyond these ranges the values of k(obs) are increased or decreased depending on the type of ionizaiton of the compound under study in appropriate pH range. The observed pH dependence of the 3H to 1H exchange is in a good quantitative agreement with ylide mechanism of the exchange reaction. According to this mechanism the 3H--1H exchange takes place in N(7)-protonated forms of the purine derivatives and in zwitterions with positive charge on N(7). The ylide mechanism of the exchange reaction is also suggested by the fact that the true exchange rate constants (k+) of protonated forms of the studied compounds, calculated from the values of k(ods), rises linearly with the increase of their protonation constant (Ka1)--the tenfold increase of Ka1 leads to about four-fold rise of k+. The knowledge of 1h to 3H exchange mechanism in C(8)H groups of purine derivatives allows to estimate alterations of reactivity of the purine residues in polynucleotides and nucleic acids depending on their conformation.
Mol Biol (Mosk)
PMID:[Kinetics and mechanism of the 3H to 1H in C(8)H groups of purine derivatives]. 0 30

Influence of pH on absorbance and CD-spectra of DNA in PEG-containing water-salt solutions has been studied. The changes in the spectra appeared due to disturbance of the DNA secondary structure upon acidification of the medium proir to or after DNA compactization. If acidification preceeds DNA compactization an intense negative band in the CD spectrum inherent to the compact particles is observed at pH values 7-4. The intensity of the band decreases with an increase of the acidity. The size of the compact particles as evaluated from the dependence of the apparent optical density on the wavelength value remains unchanged (about 1200 A). If the solution is strongly acidified (pH 4.0-2.8) and a considerable disturbance in the DNA secondary structure takes place a negative band in the CD spectrum completely disappears. If one acidifies a solution containing preformed DNA compact particles a decrease of the intensity of the CD negative band starts at lower pH values (less than 2.8). This process is accompanied by an increase of the size of the particles. Acidic "denaturation" of DNA within the compact particles (pH approximately 2.5) is followed by a dissappearance of the CD negative band and a considerable increase of the particle size. The data obtained indicate that the specific arrangement of DNA strands manifested in a CD negative band depends on the defects in the DNA secondary structure.
Mol Biol (Mosk)
PMID:[The compact form of DNA in solution. IV. The effect of secondary structure defectiveness on the arrangement of double-chained DNA molecules into compact particles]. 0 1

Some physico-chemical properties of lecithin lyposomes and the effects of pH, temperature and ionic strength changes are studied by ESR using hydrophobic and hydrophylic nitroxyl radicals as spin probes. The structure differences between outer and inner layers of bilayer liposomes are observed using auxiliary water soluble paramagnetic complex and attributed tentatively to the different curvature signs of both layers. Lower estimates of transversal diffusion rates of both probes throught the membrane are obtained using exchange broadening technique and water soluble reducing agent. The limiting step in this diffusion is revealed, caused by the transport of a charged group of the diffusing molecule through the hydrophobic membrane space.
Mol Biol (Mosk)
PMID:[A study of the physico-chemical properties of lecithin membranes using hydrophobic and hydrophilic spin probes]. 0 47

1. Intracellular hydrogen ion activity, [H+]i, was extimated in human erythrocytes and in nucleated avian erythrocytes from measurements of the distribution of ammonia and 5,5'-dimethyloxazolidine-2,4'-dione (DMO) between intracellular and extracellular fluid. 2. In human erythrocytes there was no difference between values for [H+]i derived from measurements of either DMO or ammonia. 3. In avian erythrocytes, [H+]i(ammonia) was consistently greater than [H+]i(DMO), indicating significant acid-base heterogeneity of the intracellular water. The degree of heterogeneity was assessed by reference to a theoretical model of two compartments of equal size. 4. Experiments with nuclei isolated from avian erythrocytes suggested that DMO is not bound to nucleoproteins, and that the nucleus may be more acidic than the cytoplasm.
Clin Sci Mol Med 1976 Aug
PMID:Intracellular acid-base heterogeneity in nucleated avian erythrocytes. 0 34

The effect of sampling conditions on the levels of adenine nucleotides, pyridine nucleotides, glycolytic intermediates and related metabolites in yeast has been studied. A systematic examination of the conditions for harvesting has shown that it can be best accomplished by rapid filtration. Delays in the handling for removal of the medium, as is usual in the process of obtaining a number of data reported in the literature, lead to important changes in some of the metabolites examined. It is also shown that when a washing is imperative it can be carried out with a methanol-water mixture (50/50, v/v) cooled at -40 degrees without loss of intracellular concentrations of non-readily diffusible metabolites. On the basis of this experience the outline of a generally applicable procedure is presented.
Mol Cell Biochem 1976 Nov 30
PMID:Determination of intermediary metabolites in yeast. Critical examination of the effect of sampling conditions and recommendations for obtaining true levels. 1 64

1. Chronic administration of frusemide in large doses of 4 mg day-1 kg-1 for 3 weeks caused a significant reduction of cell water in rabbit cardiac and skeletal muscle. Intracellular Na+ concentration, intracellular pH and extracellular space was unchanged in both tissues. Intracellular K+ concentration increased slightly in both cardiac and skeletal muscle. 2. It is concluded that frusemide does not reduce intracellular K+ concentration in cardiac or skeletal muscle of normal animals receiving a normal oral potassium intake.
Clin Sci Mol Med 1977 Jun
PMID:The effect of chronic frusemide administration on intracellular potassium, sodium and pH of cardiac and skeletal muscle. 1 16

1. A method for measuring intracellular pH and bicarbonate concentration of human muscle is described. 2. Muscle biopsies from the quadriceps muscle of 13 healthy subjects at rest were analysed for acid-labile carbon dioxide and volume of extra- and intra-cellular water. Extracellular water volume was estimated from the chloride content and intracellular water volume from the potassium content, or alternatively derived from the sample weight. 3. The measured total carbon dioxide content in muscle was 9-84+/-1-39 mmol/kg. 4. Assuming a normal membrane potential (88 mV) and PCO2 of muscle equal to venous blood, calculated intracellular pH was 7-00+/-0-06 and intracellular bicarbonate concentration was 10-2+/-1-2 mmol/l of water.
Clin Sci Mol Med 1977 Nov
PMID:Intracellular pH and bicarbonate concentration as determined in biopsy samples from the quadriceps muscle of man at rest. 2 20

1. In seventeen patients with untreated essential hypertension the sodium and water contents of leucocytes were significantly increased, whereas the rate constant for ouabain-sensitive sodium efflux was significantly reduced. 2. These abnormalities were not found in fourteen other patients with well-controlled hypertension. 3. Preliminary observations in accelerated hypertension suggest a different pattern of abnormality in leucocyte sodium metabolism.
Clin Sci Mol Med Suppl 1975 Jun
PMID:Abnormal sodium transport in leucocytes from patients with essential hypertension and the effect of treatment. 2 75


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