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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

1. Binding isotherms of equilibrium solution concentration of bromosulphthalein (BSP) determined on the number of moles of BSP bound per mole of human serum albumin (HSA) in 310 ideal milliosmolar pH 7.4, Krebs-Henseleit and Krebs improved mammalian Ringer number 1 buffers at 37 degrees C were determined using continuous diafiltration. The albumin concentration range was from about 10 to 30 g/litre.2. The results indicate a competition between HSA polymerization and HSA binding BSP, confirming in more physiological conditions, the findings of Crawford, Jones, Thompson & Wells (1972) with pH 7.4 phosphate buffer.3. The results in Krebs-Henseleit buffer were markedly different from those in Krebs mammalian Ringer buffer and it is suggested that the differences in ionic composition influence the HSA conformation and so affect the competition between HSA polymerization and HSA binding BSP.
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PMID:Further studies of binding of bromosulphthalein sodium by human serum albumin: effects of albumin concentration and buffer composition. 471 13

Factors responsible for the high lipogenic activity of rabbit serum were investigated using an assay procedure based on the gravimetric determination of the 24 hr increase in cell lipid. Cellular synthesis of fatty acids was inhibited by the presence of serum in the assay medium. Approximately 90% of the increase in cell lipid produced by serum fractions was due to triglyceride accumulation. Fractionation of rabbit serum by precipitation with ammonium sulfate or by ultracentrifugation in high density medium, both indicated that three-quarters of its lipogenic activity was associated with albumin. The lipoproteins prepared by ultracentrifugation also exhibited about one-half the activity of whole serum. The lipogenic activity of albumin was confirmed by the high potency of the albumin isolated in a nearly pure form from proteins of d>1.21 by precipitation with trichloroacetic acid and extraction with ethanol. As judged from chemical and isotopic analysis, neither the lipid content nor the lipid composition of the albumin was appreciably altered during its isolation. Of the albumin-bound lipids, only the free fatty acids, as determined by DEAE column chromatography, were present in an amount sufficient to account for the observed increase in cell triglycerides. In control experiments with horse serum of low lipogenic activity, the proteins of d>1.21 also possessed low activity in conjunction with a low content of free fatty acid. However, the albumin isolated from the latter preparation exhibited the high lipogenic activity of rabbit serum albumin. Chemical and isotopic analysis of the recovered horse serum albumin revealed that its free fatty acid content was the same as that of rabbit serum albumin. These results indicated that the isolation of horse serum albumin was attended by a substantial increase in its free fatty acid content. When the rabbit serum and horse serum content of media were adjusted to provide equivalent concentrations of albumin-bound fatty acids, the rabbit liver cells grown on the former media accumulated more lipid than cells grown on the latter media. This difference was shown to be due to the higher concentration of albumin per micro mole of fatty acid in horse serum as compared with rabbit serum. Consequently, the albumin to fatty acid ratio also controls the lipogenic activity of a serum. A linear relationship is presented which relates the cell lipid content to the molar ratio of albumin to free fatty acids and to the absolute concentration of free fatty acids in the medium.
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PMID:Identification of albumin-bound fatty acids as the major factor in serum-induced lipid accumulation by cultured cells. 553 19

1. A study of the mode and mechanism of Cu(2+)-induced mitochondrial swelling was carried out. 2. Mitochondrial swelling curves (E(520) turbidity changes) were obtained as a function of [Cu(2+)], pH, temperature and mitochondrial protein concentration. ED(50) was approx. 70mmumoles of Cu(2+). Calculation of the activation energy from the Arrhenius equation gave a value of 22900cal./mole per degree with Q(10) 4.02. 3. No lipid peroxides were formed during swelling. 4. Changes in oxygen consumption (Clark-type electrode) were dependent on the substrate used, but revealed no increased uptake in presence of Cu(2+). 5. Cu(2+)-induced swelling was inhibited by EDTA, 8-hydroxyquinoline, cyanide, citrate, bovine serum albumin, ATP, glutamate, GSH, dithiothreitol and sucrose. Azide, Amytal, antimycin A and oligomycin had no significant effect. Potentiation of swelling was seen with ascorbate, 2,4-dinitrophenol and succinate. 6. The occurrence of different types of mitochondrial swelling and the suggestion that Cu(2+)-induced swelling is mediated through a stoicheiometric interaction with a thiol-containing membrane receptor are discussed.
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PMID:Studies of copper ion-induced mitochondrial swelling in vitro. 566 92

Tritium-labeled digitoxin, digitoxigenin, digoxin, and digoxigenin of established purity and chemcal authenticity were used to study the binding of these compounds to human plasma proteins. 97% of digitoxin in plasma was nondialyzable. Continuous flow paper electrophoresis of plasma containing digitoxin and dialysis experiments in which human serum albumin competed for the glycoside with plasma or plasma protein fractions demonstrated that digitoxin was almost exclusively bound by albumin. Equilibrium dialyses revealed that the interaction was characterized by a single binding site on the albumin molecule and an association constant of 9.62 x 10(4) liter/mole at 37 degrees C. At 1 degrees C the association constant was 4.64 x 10(4) liter/mole. The interaction therefore was endothermic; the gain in enthalpy of 3.5 kcal/mole and the free energy change of - 7.06 kcal/mole was derived from a large change in entropy of 33.8 cal/mole per degrees K. The direction of these thermodynamic changes suggested the formation of a hydrophobic bond between digitoxin and albumin. Quenching of the fluorescence of albumin by digitoxin indicated that the conformation of albumin was altered by the binding process.Digitoxigenin, its mono- and didigitoxosides, digoxin, and digoxigenin competed with digitoxn for its binding site on albumin. The affinity of the mono- and didigitoxosides for the site was equal to that of digitoxin, but that of digitoxigenin was only one-third as great. The ability of the digitoxose residues of the glycosides to enhance binding to albumin was also observed with digoxin, which was more extensively bound by the protein than digoxigenin. At concentrations of 2 mug/ml or less in plasma, only 23% of digoxin was bound. Albumin, which interacted with digoxin with an apparent association constant of 9 x 10(2) liter/mole at 37 degrees C, was entirely responsible for the binding. Lowering the temperature from 37 degrees to 1 degrees C decreased the fraction of digoxin bound to albumin by two-thirds. The marked difference in avidity of digitoxin and digoxin for serum albumin is reflected by the higher plasma concentrations, lower rate of urinary excretion, and longer half-time of digitoxin as compared to those of digoxin when these compounds are administered to man.
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PMID:Binding of digitoxin and some related cardenolides to human plasma proteins. 577 Nov 86

Specific antibodies directed against Ptychodiscus brevis 'brevetoxins' have been produced in a goat. The haptenic toxin T34 was chemically reduced to toxin T17, covalently-linked to succinic acid via anhydride coupling, and coupled to bovine serum albumin using standard carbodiimide condensation procedures. The hapten coupling efficiency ranged from 10.4 to 13.5 moles of toxin bound per mole of protein. Antibody titers were directly related to the frequency of immunization, and weekly intervals appeared optimum for maintaining adequate titers. [3H]Brevetoxin T17 is displaced in a competitive manner from the antibody-antigen complexes by unlabeled toxin, but the antibodies do not distinguish between T17 and T34. The sensitivity achieved, using purified brevetoxins as competitive inhibitors of [3H]T17 binding, was 600 picograms. The assay linearity ranged from 1.5 to 48 ng.
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PMID:Specific antibodies directed against toxins of Ptychodiscus brevis (Florida's red tide dinoflagellate). 608 45

Dibrommercuryfluoresceine (DBMF) reacts stoichiometrically and quantitatively with the thiol group of cysteine, glutathione and thioglycolic acid respectively, at pH 7.0. Polarographical and spectrometrical titrations clearly show that in the spectra of the investigated mercaptides the wave length of the first absorption maximum of DMBF (507 nm) remains unchanged but the molar extinction coefficient increases by approximately 20%. Serum albumin, ovalbumin, beta-lactoglobulin and glyceraldehydephosphatedihydrogenase, after incubation with DBMF, form adducts with the dye from which the pure mercaptide complexes were separated by means of column chromatogrphy. These complexes were separated by means of column chromatography. These complexes show a bathochromic shift (520 nm) of the dye band which is decreased now by 50%. The molar extinction coefficient epsilon 520 has been determined from 32,000 to 33,850. On the basis of these values SH-contents of the four proteins were obtained which are in good accordance with data previously published in the literature. No selective reaction, f.i. with more accessible or/and reactive SH-groups was observed. After 30 min incubation with DBMF and washing with isotonic phosphate buffer, native animal tumor cells show in the main absorption band the bathochromically shifted dye maximum. A first temptative estimation of the protein SH-groups yielded 1.7-2.1 X 10(-14) mole SH/single cell. This result lies between the SH-content determined microspectrometrically on cells stained with DDD-Fast Blue B (1.1-1.55 X 10(-14)) and macroscopically on cell homogenates with DTNB (3.1 X 10(-14)). Up to now, no certain information can be given whether or to what extent unspecific absorption effects possibly might be involved in the data obtained with DBMF treated cells, but interaction with nucleic acids can be excluded with certainty on the basis of relevant model experiments.
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PMID:[Quantitative determination of sulfhydryl groups with "mercurochrome" (author's transl)]. 615 32

Plasma membrane isolated from rat sperm cells after incubation in vitro had a significantly lower cholesterol/phospholipid mole ratio when the medium contained serum albumin. Transfer of albumin-bound phospholipids to the membrane can largely account for this effect. The result is broadly consistent with a previously proposed model for albumin-induced destabilization of sperm membrane (capacitation) and its reversal by seminal plasma membrane vesicles. Albumin also decreased sialic acid and, more specifically, ganglioside levels, presumably by promoting release of sperm neuraminidase. Cholesteryl ester comprised up to 0.5 mol/mol of cholesterol in these plasma membrane preparations.
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PMID:Studies on the mechanism of capacitation: albumin-mediated changes in plasma membrane lipids during in vitro incubation of rat sperm cells. 644 58

In contrast to analysis for competitive binding in enzyme kinetics, no linear plot for analysing competitive binding of two ligands to a protein, where the concentrations of the three reactants are comparable, seems to exist. In the present communication it is shown that in this situation a linear plot can be obtained by the use of the simple equation VA/VB = KA/KB X [Af]/[Bf], where VA and VB are the average number of moles of ligand A and ligand B bound per mole of protein, respectively; [Af] and [Bf] are the concentrations of free ligand A and free ligand B, respectively; and KA and KB are the corresponding association constants. The plot is commented on both theoretically and experimentally using ligand binding to human serum albumin as an example.
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PMID:Graphical analysis of competitive binding of comparable concentrations of ligand, inhibitor and protein. Ligand binding to serum albumin. 662 38

The polypeptide molecular weight of lecithin-cholesterol acyltransferase (LCAT) (45000) was obtained by deducting the weight of carbohydrate moiety (25%, w/w) from the total molecular weight of 60000. LCAT was found to have a relatively high content of glutamic acid, aspartic acid, glycine, and leucine residues and four half-cystines. The carbohydrate content was found to be about 25% (w/w): hexoses, 13%; hexosamines, 6.2%; and sialic acid, 5.4%. The total number of 408 amino acid residues per mole and the mean residue weight of 110.3 were found. From fluorescence spectroscopy analysis, 6-7 mol of tryptophan were found per mole of LCAT in 10 mM phosphate (pH 7.4). However, when LCAT was digested by the mixture of chymotrypsin and pronase the tryptophan residues increased to 10-11 mol/mol of LCAT, which agrees well with data obtained previously by ultraviolet absorption spectroscopy. A partial specific volume of 0.707 mL/g was determined by compositional analysis. Human LCAT was found to have a relatively high extinction coefficient (E1%1cm) of 21 at 280 nm and neutral pH. Two residues of cysteine per mole of LCAT were estimated both in the presence or absence of sodium dodecyl sulfate by titration with 5,5'-dithiobis-2-nitrobenzoic acid. The enzyme showed a lower tendency to staining with Coomassie blue R-250 than bovine serum albumin. The enzyme was rapidly inactivated by diisopropyl fluorophosphate (DFP), regardless of whether the free sulfhydryl were blocked or not. The enzyme was also irreversibly inhibited by cysteine above concentrations of 1 mM.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Characterization of lecithin-cholesterol acyltransferase from human plasma. 3. Chemical properties of the enzyme. 662 99

The semireduced, semioxidized, and OH(.)-adduct radicals of bilirubin (BR) and biliverdin (BV) have been characterized using pulse radiolysis techniques. Laser flash photolysis (265-nm) of these pigments led to monophotonic photoionization with quantum yields of 0.08 for BR and 0.03 for BV. No evidence for triplet formation or for photoisomerization was found after 265-nm laser excitation. However, 347-nm excitation of BR in chloroform led to simultaneous photoisomerization and radical formation, but the radicals are thought to have originated from a pathway other than photoionization. The relevance of these observations to BR photoreactivity is discussed. BR radical ions in alkaline solution did not react with tryptophan (TrpH), but the semioxidized TrpH radical oxidized BR with k = 4.3 X 10(8) dm3 mole-1 sec-1. When human serum albumin (HSA) was oxidized using radiolytically generated azide radicals, a radical transformation involving TrpH and TyrOH residues occurred with k = 3.8 X 10(3) sec-1. When BR was complexed with the protein the transformation rate was reduced to 1.6 X 10(3) sec-1. This was interpreted in terms of a conformational change in the protein. Identification of the probable residues involved provided information about the primary BR binding site which was consistent with an earlier report.
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PMID:The radical ions and photoionization of bile pigments. 665 16


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