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PubMed2000

Effect of dipyridamole on the recombination kinetics between photooxidized bacteriochlorophyll and photoreduced primary quinone in reaction centres of purple bacteria.

The action of dipyridamole (DIP) on dark recombination between the photooxidized special pair bacteriochlorophyll BChl2+ and reduced primary quinone acceptor Q(A)- in the reaction centres (RCs) of the bacteria Rhodobacter sphaeroides was studied in the presence of different detergents (LDAO, Triton X-100, sodium cholate, sodium dodecyl sulfate). DIP accelerated this reaction approximately 4-5-fold. In RCs with the extracted H-subunit, the effect of DIP was observed at lower concentrations. The possibility of modification of the RC structure-dynamic state by DIP (including changes in RC hydrogen bonds) is proposed. The modification obviously disturbs the processes of the long-life electrostatic stabilization of Q(A)-.

Bacteriochlorophylls↗

PubMed1988

Phospholipid requirement for expression of ice nuclei in Pseudomonas syringae and in vitro.

Delipidation of partially purified outer membranes of Pseudomonas syringae by various delipidating agents resulted in a significant loss of ice nucleation activity associated with the cell envelopes of this and other ice nucleation active bacteria. Lipopolysaccharide depletion of such membranes caused no reduction in ice nucleation activity. Both phospholipid content and ice nucleation activity of membranes were decreased by a similar fractional amount with time after treatment with phospholipase A2. A proportional quantitative relationship between loss of ice nucleation activity and lipid removal with increasing concentrations of sodium cholate and sodium dodecyl sulfate (SDS) was also observed. Significant linear relationships between the amount of lipid removed by phospholipase A2, sodium cholate, and SDS and the loss of ice nucleation activity in P. syringae outer membranes were observed. However, the slopes of these linear relationships for membranes treated with phospholipase A2 (m = 0.80), SDS (m = 0.94), and sodium cholate (m = 0.53) differed. The lower slope value for cholate-treated membranes indicated a partial substitution of sodium cholate for the phospholipids removed. The ice nucleation activity of delipidated outer membranes was restored by reconstitution with various phospholipids in a cholate dialysis procedure. Lipid classes differed in their ability to restore ice nucleation activity to sodium cholate-treated outer membranes. These results suggest that a hydrophobic environment provided either by lipids or certain detergent micelles is required for proper assembly and structural organization of an oligomeric ice protein complex enabling its expression as an ice nucleus.

Cell Membrane↗

PubMed1991

On the effect of lysophosphatidylcholine, platelet activating factor and other surfactants on calcium permeability in sarcoplasmic reticulum vesicles.

The effect of low concentrations of lysophosphatidylcholine (LPC), platelet-activating factor (PAF) and other surfactants (Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate) on membrane permeability of native sarcoplasmic reticulum vesicles and sarcoplasmic reticulum lipid vesicles, has been studied. Triton X-100, C12E8, sodium dodecyl sulfate, sodium cholate and sodium deoxycholate were all able to permeabilize membranes at concentrations of surfactants below their critical micellar concentration (CMC) in both lipid and native vesicles, being the K0.5 of calcium release from native vesicles lower than that from lipid vesicles. The values of these K0.5 were well correlated with the corresponding CMC values for each type of membrane. However, both LPC and PAF behaved in a different way since, although they induced permeabilization of the native vesicles at values of K0.5 close to their CMC, their K0.5 values for permeabilizing vesicles, prepared by using lipids extracted from sarcoplasmic reticulum, were much higher than their corresponding CMC.

Animals↗

PubMed1981

Effects of pH shifts, bile salts, and glucose on sporulation of Clostridium perfringens NCTC 8798.

The sporulation of Clostridium perfringens NCTC 8798 was studied after exposing vegetative cells to: pH values of 1.5 to 8.0 in fluid thioglycolate broth (for 2h) and then transferring them to Duncan-Strong (DS) sporulation medium; sodium cholate or sodium deoxycholate (0.3 to 6.5 mM) in DS medium; or Rhia-Solberg medium with 0.4% (wt/wt) starch, glucose, or both added at 0 to 55 mM. At pH 1.5, no culturable heat-resistant spores were formed. For cells exposed to pH 3.0, 4.0, 5.0, or 6.0, increases in heat-resistant spores were not seen until after a lag of 12 to 13 h, whereas the lag was only 2 to 3 h for cells exposed to pH 7.0 or 8.0. Maximal spore crops were produced after only 6 to 8 h for cells exposed to pH 7 or 8, but 16 to 18 h was required for production of maximal spore crops by cells exposed to the lower-pH media. The addition of sodium cholate (3.5 to 6.5 mM) to DS medium only slightly reduced the culturable heat-resistant spore count from 1.9 X 10(7) to 3 X 10(6)/ml. The addition of 1.8 mM or more sodium deoxycholate reduced the culturable heat-resistant spore count to less than 10/ ml. When either starch or glucose alone was added to Rhia-Solberg medium there was no production of culturable heat-resistant spores, but a combination of 0.4% (wt/wt) starch and 4.4 mM glucose yielded 6 X 10(5) spores/ml. The spore production remained at this level for glucose concentrations of 6 to 22 mM, but then declined to about 3 X 10(3) spores per ml at higher concentrations.

Cholic Acids↗

PubMed1976

Drop weight variation in an automated collection procedure and its relationship to apparent surface tension.

A drop counter-regulated fraction collector yields samples containing equal numbers of drops. Such fractions vary slightly in weight depending on experimental conditions such as surface tension. Provided that variables such as flow rate and eluate density remain constant, apparent surface tension may be estimated directly from the weights of eluate fractions obtained from gel filtration experiments. The detergents sodium cholate and sodium lauryl sulphate significantly decreased drop weights in this system. Following gel filtration on Sepharose 4B, sodium cholate eluted in the fractions containing low molecular weight material. It eluted in the same position when pre-mixed with human plasma. Normal plasma was found to contain two surface tension-reducing components with apparent molecular weights of 3-10(6) and 1-10(5). The apparent surface tension of whole human plasma was found to be time dependent and decreased as the flow rate was reduced.

Blood↗

PubMed1981

Monoclonal antibodies as probes of acetylcholine receptor structure. 1. Peptide mapping.

The isolated subunits of the acetylocholine receptor from Torpedo californica were digested with proteolytic enzymes, and the resulting polypeptide fragments were analyzed by gel electrophoresis. We have identified those fragments which contain carbohydrate and those from the alpha subunit which are labelled with the acetylcholine binding site specific reagent [4-(N-maleimido)benzyl]tri[3H]methylammonium iodide. We have tested several monoclonal antibodies raised to the acetylcholine receptor from torpedo, some of which react with the denatured subunits [Tzartos, S.J., & Lindstrom, J.M. (1980) Proc. Natl. Acad. Sci. U.S.A.77, 755; Tzartos, S.J., & Lindstrom, J.M. (1981) in Monoclonal antibodies in Endocrine Research (Fellows, R., & Eisenbarth, G., Eds.) Raven Press (in press)]. The binding specificities of these antibodies to radioiodinated proteolytically generated fragments of the alpha subunit were determined by immunoprecipitation followed by gel electrophoresis. The antibodies tested fell into at least three main groups on the basis of their binding specificities. These antibodies were also tested for their capacity to bind to acetylcholine receptor solubilized in Triton X-100, sodium cholate, or sodium cholate supplemented with exogenous lipids. A monoclonal antibody raised to the denatured delta subunit, was tested for its ability to select radioiodinated proteolytic fragments of these subunits. These molecules provide probes for many sites on the acetylcholine receptor with affinities and specificities comparable to alpha-neurotoxins.

Animals↗

PubMed1979

Lipid requirements for the structure and function of the fatty acid synthetase complex from Ceratitis capitata.

Lipid content of purified fatty acid synthetase preparations from the Dipterous Ceratitis capitata correlated with the enzyme activity. Delipidation of the enzyme by extracting with a series of organic solvents rendered a protein without any residual activity and the treatment with phospholipase A2 for 30 min reduced the activity to 10%. Addition of lipid classes to either the native enzyme or the phospholipase-treated preparation enhanced the activity in a different manner, phosphatidylethanolamine being the most effective lipid. The role of the lipids in the lipoprotein structure of the complex was studied by circular dichroism spectra of the native enzyme and in the presence of a concentration range of urea, guanidinium chloride, sodium dodecyl sulfate, sodium cholate, and sodium chloride. 3 M urea and 1.5 M guanidinium chloride induced a conformational transition of the lipoprotein that lost its alpha-helical structure at higher concentrations of both reagents. Sodium dodecyl sulfate and sodium cholate had little effect on the alpha-helical structure, although both reagents induced the loss of enzyme activity. Cholate had essentially the same effect as phospholipids on the maintenance of the native structure but it was unable to support the enzyme activity.

Animals↗

PubMed2002

Cholate-induced dimerization of detergent- or phospholipid-solubilized bovine cytochrome C oxidase.

Bovine heart cytochrome c oxidase (CcO), solubilized by either nonionic detergents or phospholipids, completely dimerizes upon the addition of bile salts, e.g., sodium cholate, sodium deoxycholate, or CHAPS. Bile salt induced dimerization occurs whether dodecyl maltoside, decyl maltoside, or Triton X-100 is the primary solubilizing detergent or the enzyme is dispersed in phosphatidylcholine, phosphatidylethanolamine, or mixtures thereof. In each case, complete CcO dimerization can be verified by sedimentation velocity and sedimentation equilibrium after correction for bound detergent and/or phospholipid. The relative concentration of the bile salt is critical for production of homogeneous, dimeric CcO. For example, enzyme solubilized by 2 mM detergent requires an equal molar concentration of sodium cholate. Similarly, enzyme dispersed in 20 mM phospholipid requires 50 mM sodium cholate, concentrations that are commonly used to reconstitute CcO into small unilamellar vesicles. Bile salts do more than just stabilize dimeric CcO and prevent detergent-induced dissociation into monomers. They are able to completely reverse detergent-induced monomerization and cause completely monomeric CcO to reassociate. Dimeric CcO so generated is no more stable than the original complex and easily dissociates into monomers if the bile salt is removed. The dimerization process is dependent upon a full complement of subunits; e.g., if subunits VIa and VIb are removed, the resulting monomeric CcO will not reassociate upon the addition of sodium cholate. These results support four important consequences: (1) dissociation of dimeric CcO into monomers is reversible; (2) stable dimers can be produced under solution conditions; (3) dimers can be stabilized even at relatively high pH and low enzyme concentration; and (4) subunits VIa and VIb are required for dimerization.

Animals↗

PubMed1990

Sodium cholate-induced changes in the conformation and activity of rat pancreatic cholesterol esterase.

Pancreatic cholesterol esterase (CEase) regulates dietary cholesterol absorption and is activated in the presence of trihydroxy bile salts while remaining inactive monohydroxy bile salts. CEase from rat pancreas has been purified by ammonium sulfate precipitation, hydroxylapatite chromatography, and gel filtration on Sephacryl S-200/S-300 columns connected in series, and its homogeneity and Mr (55,418 +/- 288) have been determined by sedimentation equilibrium centrifugation. The effects of tri-, di-, and monohydroxy bile salts on the conformation of the purified enzyme in buffer solution and in an in vitro assay system were studied by circular dichroism spectropolarimetry. The CD spectrum of the enzyme in solution shows a curve shape suggestive of an alpha-helicity, but low mean residue ellipticity (MRE) values may indicate an important beta-turn contribution. Sodium cholate, a trihydroxy bile salt, induces a decrease in the negative MRE values of the enzyme in solution at bile salt concentrations of 70-100 nM, with no further spectral changes at concentrations as high as 1 mM. Sodium cholate concentrations higher than 1 microM also induce an increase in the enzyme's negative MRE values under activity assay conditions, which reverts toward its original value once the reaction reaches equilibrium. These latter changes are interpreted as induced by substrate binding to the enzyme followed by partial substrate depletion after the reaction reaches equilibrium. Sodium deoxycholate, a dihydroxy bile salt, induces unstable transient increases and decreases in the MRE values of CEase in buffer solution and under activity assay conditions. These changes are bile salt concentration-dependent and may reflect self-association of the protein. Sodium taurolithocholate, a monohydroxy bile salt, does not affect the CD spectrum of CEase, and neither the di- or the monohydroxy bile salt activates the enzyme.

Animals↗

PubMed2003

Micelle formation of sodium chenodeoxycholate and solubilization into the micelles: comparison with other unconjugated bile salts.

Micellization of sodium chenodeoxycholate (NaCDC) was studied for the critical micelle concentration (CMC), the micelle aggregation number, and the degree of counterion binding to micelle at 288.2, 298.2, 308.2, and 318.2 K. They were compared with those of three other unconjugated bile salts; sodium cholate (NaC), sodium deoxycholate (NaDC), and sodium ursodeoxycholate (NaUDC). The I(1)/I(3) ratio of pyrene fluorescence and the solubility dependence of solution pH were employed to determine the CMC values. As the results, a certain concentration range for the CMC and a stepwise molecular aggregation for micellization were found reasonable. Using a stepwise association model of the bile salt anions, the mean aggregation number (n) of NaCDC micelles was found to increase with the total anion concentration, while the n values decreased with increasing temperature; 9.1, 8.1, 7.4, and 6.3 at 288.2, 298.2, 308.2, and 318.2 K, respectively, at 50 mmol dm(-3). The results from four unconjugated bile salts indicate that the number, location, and orientation of hydroxyl groups in the steroid nucleus are quite important for growth of the micelles. Activity of the counterion (Na(+)) was determined by a sodium ion selective electrode in order to confirm the low counterion binding to micelles. The solubilized amount of cholesterol into the aqueous bile salt solutions increased in the order of NaUDC<NaC<NaCDC<NaDC. The first stepwise association or solubilization constants (K(1)) between a cholesterol monomer and a vacant micelle were evaluated at different bile salt concentrations. The constants were also determined for polycyclic aromatic compounds (benzene, naphthalene, anthracene, and pyrene). The corresponding DeltaG(0) value was most negative for cholesterol among the solubilizates studied, which indicated that cholesterol was thermodynamically stabilized most by solubilization into the bile salt micelles.

Bile Acids and Salts↗

PubMed2006

Spectroscopic probing of bile salt-albumin interaction.

Interaction of the bile salts, sodium cholate and sodium deoxy cholate with albumin has been probed by fluorescence and circular dichroism studies. Both covalently and non-covalently labeled protein have been used to follow the aggregation of bile salts in presence of protein and to study bile salt-protein interactions in general. Time resolved studies, in agreement with steady-state fluorescence and circular dichroism studies, indicate alteration of protein secondary structure due to positive co-operative effects in bile salt binding to protein. These studies also indicate that covalent labeling may not always be good for studying proteins as it causes alteration of protein secondary structure.

Animals↗

PubMedDate not supplied

Transepithelial electrical resistance is not a reliable measurement of the Caco-2 monolayer integrity in Transwell.

The significance of monitoring transepithelial electrical resistance (TEER) value during the study on drug absorption through Caco-2 monolayers in Transwells was re-evaluated. TEER value was monitored before, during, and after the absorption of Streptokinase (45 KD). Four enhancers--disodium ethylenediaminetetracetate (disodium EDTA), sodium cholate (NaC), sodium taurocholate (NaTC), and sodium caprate along with alpha-hemolysin (a cell membrane pore-forming toxin)--were used to signify the outcome of this study. Modified trypan blue exclusion technique was used to examine the Caco-2 cell viability throughout the absorption studies. The enhancers at the used concentration exhibited toxic effect on the Caco-2 cells as evident from the trypan blue exclusion studies. This toxic effect was not reflected by the TEER profile because TEER value dropped after the addition of the absorption enhancers. But it came back to its initial value after the cell culture media was replaced by enhancer-free media. This toxic effect was confirmed by the antiproliferation studies on the four enhancers and alpha-hemolysin against Caco-2 cells. Therefore, we concluded that the measurement of TEER is not a reliable method to determine the absorption enhancers toxicity or integrity of the Caco-2 monolayers in the Transwells.

Adjuvants, Pharmaceutic↗

PubMed1971

Fetal bile salt metabolism. I. The metabolism of sodium cholate-14C in the fetal dog.

Cholate metabolism was studied in fetal dogs 1 wk before term and was compared with cholate metabolism in adult dogs. Tracer amounts of sodium cholate-(14)C were administered to the fetus in utero by intravenous infusion over 6 hr. Fetal plasma disappearance, biliary excretion, tissue distribution, and placental transfer of cholate were measured over 10 hr. Infused cholate-(14)C was cleared rapidly from fetal plasma principally by the fetal liver and to a minor extent by placental transfer to the mother. The taurine conjugate was formed in the fetal liver and was excreted into the proximal small intestine via the biliary tree. Indirect evidence for the functioning enterohepatic circulation of bile salt in the fetus was obtained. Comparison with the results of similar experiments in adult dogs showed that the fetal liver was almost as efficient as the adult liver in the uptake, conjugation, and excretion of tracer amounts of cholate-(14)C. The maximal rate of excretion of radiolabel attained by the fetus was somewhat slower than in the adult (82.8 +/-1.4% and 96.1 +/-4.0% [mean +/-SE] of the infusion rate, respectively), and the proportion of the total dose excreted by the fetal liver during 10 hr was smaller (81.4 +/-1.3% vs. 96.6 +/-4.4%). This difference could be only partly accounted for by placental transfer (2.8 +/-0.6% of the fetal dose). Labeled cholate and taurocholate were excreted by the fetus at similar rates, which suggests that, under the conditions of study, conjugation had little influence on the rate of transfer of cholate across the liver cell. It is concluded that the fetal dog, 1 wk before birth, has a remarkably mature and efficient mechanism for the uptake and excretion of cholate.

Animals↗

PubMed1982

Molecular organization in the liquid--crystalline phases of lecithin--sodium cholate-water systems studied by nuclear magnetic resonance.

The molecular organization in the hexagonal and lamellar phases of the ternary systems lecithin--sodium cholate--water has been investigated by using a variety of nuclear magnetic resonance techniques. The main findings and conclusions are the following: (i) When calculated on a mole fraction basis, the phase equilibria are insensitive to changes in the alkyl chains of the lecithin. (ii) When incorporated into a lecithin bilayer, cholate exerts a strong perturbation on the lecithin alkyl chain order, giving a large decrease of the order parameters. (iii) This decrease of the order occurs since the average cross-sectional area per alkyl chain increases probably as a result of cholate placing itself flat on the bilayer surface. (iv) The diffusion of lecithin molecules is approximately equally rapid in the lamellar and hexagonal phases. (v) The hexagonal phase is formed by rodlike aggregates with the polar groups at the surface of the rods and with a continuous hydrocarbon core. The rods are not formed by stacking disklike mixed micelles. (vi) With the interpretations of the molecular packing and the phase structures, the observed phase equilibria are in good agreement with current theories of the factors that govern phase behavior in amphiphile--water systems.

Chemical Phenomena↗

PubMed1988

Effects of detergent on the binding of solubilized sodium channels to immobilized wheat germ agglutinin: structural implications.

The binding of the solubilized voltage-dependent sodium channel from rat brain to immobilized wheat germ agglutinin (WGA) is detergent-dependent. When solubilized in sodium cholate, only 11% of total recovered channels bound to a WGA-Sepharose column. When solubilized in Triton X-100 or CHAPS, however, 80% and 60% could bind, respectively. The effect of cholate on sodium channel binding is relatively specific: the major rat brain glycoproteins which bind to immobilized WGA are roughly the same in either Triton or cholate, as analyzed by SDS gel electrophoresis. The structural implications for the channel are discussed.

Animals↗

PubMed1981

Fluorescence studies on the lipoprotein complex of the fatty acid synthetase from the insect Ceratitis capitata.

The fatty acid synthetase complex from the insect Ceratitis capitata forms a stable lipoprotein complex. The intrinsic fluorescence of the complex was studied by observing the emission spectra with different excitation wavelengths, both in the native complex and after temperature with sodium cholate and sodium dodecyl sulfate. The excitation spectrum of the native form also was recorded. The fluorescence behavior of the native enzyme showed two families of tryptophan residues. Cholate influenced the fluorescence, suggesting that phospholipids are the conformational support at this level. The two families of fluorescing tryptophan residues were similarly accessible to quenching by acrylamide. Thermal changes in the fluorescence characteristics were observed; warming caused a decrease in the quantum yield as well as a red shift in the emission maximum. The high fluorescence remaining after the thermal transition suggested that the lipid-protein interaction was affected but maintained shielding of the fluorophore by the lipids. Fluorescent probe molecules 1,6-diphenyl-hexa-1,3,5-triene (DPH) and dansylphosphatidylethanolamine (DPE) also were used. DPH uptake was temperature dependent, with a middle point consistent with the thermal conformation transition, indicating that internal lipids are nonrandomly distributed within the complex. DPE uptake did not reach the saturation of the complex, suggesting that its solubilization sites would be located on the lipoprotein surface.

Animals↗

PubMed2001

Study of partition of nitrazepam in bile salt micelles and the role of lecithin.

The effect of trihydroxy (sodium cholate and sodium glycocholate) and dihydroxy (sodium deoxycholate and sodium glycodeoxycholate) bile salt micelles on the spectrophotometric properties and on the solubility of nitrazepam in aqueous solution, at 25.0 degrees C and at ionic strength 0.1 M in sodium chloride, has been assessed. From the results obtained it was possible to calculate the partition coefficients (Kp) of nitrazepam between aqueous and micellar phases. The partition coefficients of nitrazepam have also been determined in mixed micelles of cholate or deoxycholate with lecithin (egg yolk phosphatidylcholine), which were used as a model of the gastrointestinal tract. Drug partition was found to depend on the bile acid (number of hydroxyl groups and conjugation with glycine), and our data indicate further that addition of lecithin to bile salt micelles decreases the values of the partition coefficients in the mixed micelles at physiological pH.

Bile Acids and Salts↗

PubMed1977

[The effects of 4 detergents on the respiration of mitochondria isolated from rat liver].

The effects of these four detergents (two non-ionic: Titron X100 and Tween 80, two ionic: sodium cholate and sodium dedeoxycholate) upon the respiratory intensities of mitochondria and upon the ADP/0 and respiratory control ratios were observed. At low concentrations and in the absence of exogenous ADP, non ionic as well as ionic detergents provoked a threefold (or fourfold) increase of the respiratory intensities of mitochondria. At higher concentrations, the four detergents were inhibitory for mitochondrial oxidations in the order: Triton X 100 greater than DOC greater than cholate greater than Tween 80. At increasing doses, the four detergents progressively decreased the phosphorylating capacities of mitochondria.

Adenosine Diphosphate↗