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PubMed1991

The neuromelanin of the human substantia nigra.

The pigment of the human substantia nigra was isolated after extraction of lipids and proteins with 2% sodium cholate in 30% ethanol followed by 2% sodium dodecyl sulfate in 10% glycerol. The pigment was hydrolysed with HI or degraded by treatment with KMNO4 and the samples were examined for compounds known to derive from pheomelanin (4-amino-3-hydroxyphenylalanine, AHP and 4-amino-3-hydroxyphenylethylamine, AHPEA), or from eumelanin (pyrrole-2,3,5-tricarboxylic acid, PTCA). The HI hydrolysis yielded AHPEA in large quantities, indicating cysteinyldopamine as the main source of the pheomelanin moiety of the neuromelanin, but also trace amounts of AHP, derived from cysteinyldopa oxidation products. Dopamine and small quantities of dopa were also obtained by HI hydrolysis of the neuromelanin. The yield of PTCA was low, but the amounts observed show that part of the neuromelanin is of the eumelanin type, a fact compatible with an occasional exhaustion of the glutathione-cysteine reduction system at the site of neuromelanin formation.

Chromatography, High Pressure Liquid↗

PubMedDate not supplied

Solubilization and pharmacokinetic behaviors of sodium cholate/lecithin-mixed micelles containing cyclosporine A.

The purpose of this study was to investigate the solubilization capacity of sodium cholate/lecithin-mixed micelles and to evaluate the potential of mixed micelles as a carrier of cyclosporine A for intravenous infusion. The mixed micelles were prepared by coprecipitation technique. The formulation components and preparation procedures, which may affect the solubilization of cyclosporine A, were studied. The dilution stability of cyclosporine A-containing mixed micelles was investigated. Pharmacokinetic behaviors of mixed micelles in rabbits after intravenous infusion were compared with Sandimmun. Results showed the strategies to increase the solubility of cyclosporine A include lowering the molar ratio of sodium cholate to lecithin, increasing the concentration of lecithin, and reducing the ionic strength of the dispersion medium and temperature. The largest solubility was found to be 5.42 +/- 0.16 mg/ml. The leakage of mixed micelles in 5% glucose (5.84%) was much less than that in saline solution (36.7%). The relative bioavailability of mixed micelles versus Sandimmun was 112 +/- 20%, and statistical analysis demonstrated both preparations were bioequivalent. Sodium cholate/lecithin-mixed micelles are promising carriers in the intravenous delivery of cyclosporine A, considering their capability of large-scale production and low-toxic property.

Animals↗

PubMed2003

Separation of some chiral flavanones by micellar electrokinetic chromatography.

Micellar electrokinetic chromatography (MEKC) was applied for enantioseparation of selected flavanones, including naringin, hesperidin, neohesperidin, naringenin, hesperetin, pinostrobin, isosakuranetin, eriodictyol, and homoeriodictyol. gamma-Cyclodextrin (gamma-CD) and sodium cholate (SCh) were used as chiral modifiers inducing enantioselectivity to the background electrolyte. From among many investigated selectors only these two appeared to possess the best enantioselective properties in respect to studied flavanones. The mechanisms of their action are a little different; SCh used above critical micelle point concentration forms chiral micelles itself while gamma-CD is deprived of this property and requires addition of surfactants as, e.g., sodium dodecyl sulfate. It was found that SCh enables separation of flavanone glycosides diastereomers while separation of enantiomers of flavanone aglycones may be achieved with gamma-CD. Consideration of structural relation led to the suggestion that interaction of sugar moiety of glycosides with SCh micelles give rise to chiral recognition. MEKC appeared to be a suitable and efficient analytical tool to follow enantiomeric composition of flavanones.

Chromatography, Micellar Electrokinetic Capillary↗

PubMed2003

Small-angle neutron scattering study of the lipid bilayer thickness in unilamellar dioleoylphosphatidylcholine vesicles prepared by the cholate dilution method: n-decane effect.

Previous X-ray diffraction studies on fully hydrated fluid lamellar egg phosphatidylcholine phases indicated a approximately 10 A increase of bilayer thickness in the presence of excess n-decane [Biochim. Biophys. Acta 597 (1980) 455], while the small-angle neutron scattering (SANS) on unilamellar extruded dioleoylphosphatidylcholine (DOPC) vesicles detected substantially smaller 2.4+/-1.3 A bilayer thickness increase at n-decane/DOPC molar ratio of 1.2 [Biophys. Chem. 88 (2000) 165]. The purpose of the present study is to investigate the n-decane effect on the bilayer thickness in unilamellar DOPC vesicles prepared by the sodium cholate (NaChol) dilution method. Mixed DOPC+NaChol micelles at DOPC and NaChol concentrations of 0.1 mol/l were prepared in 2H(2)O containing 0.135 mol/l NaCl. This micellar solution was diluted in 0.135 mol/l NaCl in 2H(2)O to reach the final DOPC and NaChol concentrations of 0.008 mol/l. Thirty microliters of n-decane solution in methanol was added to 1 ml of this dispersion. After methanol evaporation, SANS was conducted on the dispersions. From the Kratky-Porod plot ln[I(Q)Q(2)] vs. Q(2) of SANS intensity I(Q) in the range of scattering vector values Q corresponding to interval 0.001 A(-2)<or=Q(2)<or=0.006 A(-2), the bilayer radius of gyration R(g) and the bilayer thickness parameter d(g)=12(0.5)R(g) were obtained. The values of d(g) indicate that the bilayer thickness increases by 2.4+/-0.9 A up to n-decane/DOPC molar ratio of 1.6. This result confirms the previous SANS findings obtained with extruded vesicles.

Alkanes↗

PubMed2000

Purification, characterization, and molecular cloning of group I phospholipases A2 from the gills of the red sea bream, Pagrus major.

Phospholipase A2 (PLA2) activity was investigated in various tissues of male and female red sea bream. In both male and female fishes, the specific activity of PLA2 in the gills was 70 times higher than that in other tissues, such as the adipose tissue, intestine, and hepatopancreas. Therefore, we tried to purify PLA2 from the gill filaments of red sea bream to near homogeneity by sequential chromatography on Q-Sepharose Fast Flow, Butyl-Cellulofine, and DEAE-Sepharose Fast Flow columns, and by reversed-phase high-performance liquid chromatography. Two minor and one major PLA2, tentatively named G-1, G-2 and G-3 PLA2, were purified, and all showed a single band with an apparent molecular mass of approximately 15 kDa by sodium dodecylsulfate-polyacrylamide gel electrophoresis. The exact molecular mass values of G-1, G-2, and G-3 PLA2 were 14,040, 14,040 and 14,005 Da, respectively. G-1, G-2, and G-3 PLA2 had a Cys 11 and were all identical in N-terminal amino acid sequences from Ala-1 to Glu-56. A full-length cDNA encoding G-3 PLA2 was cloned by reverse transcriptase-polymerase chain reaction and rapid amplification of cDNA ends methods, and G-3 PLA2 was found to be classified to group IB PLA2 from the deduced amino acid sequence. G-1, G-2, and G-3 PLA2 had a pH optimum in an alkaline region at around pH 9-10 and required Ca2+ essentially for enzyme activity, using a mixed-micellar phosphatidylcholine substrate with sodium cholate. These results demonstrate that three group I PLA2, G-1, G-2, and G-3 PLA2, are expressed in the gill filaments of red sea bream.

Adipose Tissue↗

PubMed1999

Surfactant-induced leakage from liposomes: a comparison among different lecithin vesicles.

The interactions, at sublytic concentration, of Triton X-100 and sodium cholate with sonicated and extruded liposomes of egg and soya lecithins were considered to analyze the integrity and/or the barrier efficiency of liposomal membranes. Results are discussed in terms of surfactant partition between the aqueous and the lipid phases and of the release of a fluorescent hydrophilic probe. Phospholipid nature and liposome size influence detergent partition, whereas the content release is mainly affected by the surfactant mole fraction in the bilayer, and by the liposome size.

Detergents↗

PubMed2005

Identification of extracellular lipases/esterases produced by Thermus thermophilus HB27: partial purification and preliminary biochemical characterisation.

Thermus thermophilus HB27 produces important levels of extracellular lipolytic activity when grown for 30 h at 70 degrees C in a complex medium. A method to detect esterase activity in these samples after non-reducing SDS-polyacrylamide electrophoresis was developed. The method, that implies the renaturalisation of the enzymes in the SDS-gels by washing with Triton X-100 at high temperatures, allowed detecting three esterases with different molecular weights (108, 62 and 34 kDa, respectively). The electrophoretic mobility determined under different experimental conditions suggested that the 34- and 108 kDa-esterases might correspond with two oligomeric states of a sole enzyme (monomer and trimer). Dissociation of the trimer into the monomer started when the samples were heated at temperatures higher than 60 degrees C in the presence of sodium dodecyl sulphate. Evidences were found that indicated the independent nature of the 62 kDa-esterase. A method to purify these enzymes from postincubates of T. thermophilus HB27 was developed following three steps: sodium cholate treatment, ethanol/ether precipitation and hydrophobic chromatography. In this way, an enzyme solution was obtained that contained the identified esterases/lipases. The partially purified enzymes showed an optimum of activity for the hydrolysis of p-nitrophenyl laurate at alkaline pH values and 80 degrees C, a high thermal stability and were very stable in the presence of high concentrations of isopropanol.

2-Propanol↗

PubMed2000

Quantitative determination of zwitterionic detergents using salt-induced phase separation of Triton X-100.

Zwitterionic detergents interfere with the salt-induced phase separation for nonionic detergents in a concentration-dependent manner by shifting the normal cloud point of nonionic detergents to a higher ionic strength at room temperature. This phenomenon was used to determine the concentration of the zwitterionic detergents CHAPS, CHAPSO, and sulfobetaine SB-12 in solution by titration with ammonium sulfate in the presence of Triton X-100. Among the ionic detergents tested, the method was only applicable to sodium cholate. The assay can be used to control the removal of zwitterionic detergents during the reconstitution of membrane proteins in liposomes. However, it cannot be used to determine the specific binding of zwitterionic detergents to highly diluted, pure membrane proteins because of the limited sensitivity. Neither proteins nor phospholipids interfered with this method at concentrations up to 20 mg/ml of test solution (human serum albumin) or 10 mg/ml (phospholipids), respectively. Since the assay is based on the competition between salts and nonionic detergents for water molecules, it is important to equalize the ionic strength of samples and calibration standards.

Cholic Acids↗

PubMed2002

Exposure to octylphenol increases basal testosterone formation by cultured adult rat Leydig cells.

4-Tert-octylphenol (OP) is a breakdown product of 4-tert-octylphenol ethoxylate, which is a surfactant additive widely used in the manufacture of a variety of detergents and plastic products. OP has been reported to exhibit weak estrogenic activity in many assay systems. The studies described herein examined an unusual effect of OP in increasing constitutive testosterone levels of cultured Leydig cells from young adult rats. The increase in testosterone was both dose and time sensitive, and this response was observed in medium lacking both calcium and magnesium and containing a membrane-permeable calcium chelator, suggesting that the increase in testosterone was not mediated by an increase in the permeability of extracellular calcium into cells or the redistribution/release of calcium from intracellular stores, respectively. Cellular cAMP levels also were unaffected by OP alone in cultured Leydig cells. Furthermore, initial exposure to 2000nM OP alone for 4h did not alter the subsequent conversion of endogenous cholesterol or exogenously added 22 (R)hydroxycholesterol to testosterone, suggesting that the increase in testosterone was not due to the enhanced availability of endogenous cholesterol or an increase in cholesterol side-chain cleavage activity, respectively. The increase in testosterone also was observed in the presence of the pure estrogen antagonist, ICI 182,780, or a 5alpha-reductase inhibitor, suggesting that this effect of OP was not mediated through the estrogen receptor alpha or beta pathway or by inhibition of Leydig cell testosterone metabolism, respectively. In addition, exposure of cells to comparable concentrations of two different detergents, Triton X-100 or sodium cholate, did not increase testosterone levels, suggesting that this effect of OP was not due to its potential detergent qualities. Although these studies did not identify specific mechanism(s) that increase constitutive testosterone levels by OP, they identify specific pathways that appear not to be involved. The physiological relevance of this observation is not known; nevertheless, they illustrate potential diverse actions of OP in modulating the level of androgen secreted by Leydig cells, and they emphasize that some actions of OP do not appear to be mediated through the estrogen receptor alpha or beta pathway.

Animals↗

PubMedDate not supplied

Hydrolysis of native poly(hydroxybutyrate) granules (PHB), crystalline PHB, and artificial amorphous PHB granules by intracellular and extracellular depolymerases.

Native poly(hydroxybutyrate) (PHB) granules, purified PHB and artificial amorphous PHB granules were examined as putative substrates for hydrolysis by the intracellular depolymerase system of Rhodospirillum rubrum and the extracellular depolymerase of Pseudomonas lemoignei. The R. rubrum depolymerizing system requires pretreatment of granules with a heat stable 'activator' fraction; the activator can be replaced by mild trypsin treatment. Artificial granules were prepared with a cationic detergent, cetyltrimethylammonium bromide (CTAB) and an anionic detergent, (sodium cholate). Cholate and CTAB PHB granules were hydrolyzed by both enzyme systems; however, some differences were noted. Cholate granules were hydrolyzed in the absence of the R. rubrum activator fraction. Activator was required for the hydrolysis of CTAB granules but could be replaced by heparin in the extracellular depolymerase system but not in the intracellular depolymerase system. A Triton X-114 extract of native PHB granules inhibited the hydrolysis of trypsin-activated granules by the intracellular depolymerase. The inhibition was reversed by the activator fraction. Detergent extracts of granules activated with the R. rubrum activator were unable to inhibit the hydrolysis of trypsin-activated granules. These data suggest that the activator acts to modify an inhibitor present on native granules.

Bacillus megaterium↗

PubMed2003

Stacking and separation of enantiomers by acetonitrile-salt mixtures in micellar electrokinetic chromatography.

The feasibility of employing the "acetonitrile stacking" method in micellar electrokinetic chromatography (MEKC) for the on-line preconcentration and separation of enantiomers is demonstrated for the first time. The effects of various experimental parameters on the stacking and separation of three different pairs of optical isomers, i.e., two substituted naphthyl enantiomers and one dansylated-DL-amino acid, were examined. In particular, the effectiveness of the addition of acetonitrile and salt in the sample matrix to induce narrowing of the analyte bands was investigated in the presence of sodium cholate as the chiral surfactant micelle in the separation buffer. For example, it was found that the presence of both acetonitrile and 1% NaCl in the sample matrix (volume ratio = 2:1) led to a significant improvement of the peak height and resolution for the MEKC separation of a pair of R(-)/S(+)-1,1'-binaphthyl diyl hydrogen phosphate enantiomers when the injection sample size was relatively large (e.g., 12% capillary volume). Furthermore, the feasibility of combining salting-out solvent extraction (off-line) and acetonitrile stacking (on-line) as a novel approach for sample preconcentration in capillary electrophoresis was also demonstrated.

Acetonitriles↗

PubMed2005

Separation and determination of phthalates by micellar electrokinetic chromatography.

A method has been developed for the separation and determination of dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DBP), di-(2-ethylhexyl) phthalate (DEHP) and di-n-octyl phthalate (DnOP) by micellar electrokinetic chromatography (MEKC). The baseline separation of phthalates was achieved by using a buffer of 100 mM sodium cholate, 50 mM borate and 15% methanol (pH 8.5). The optimized MEKC method was used to quantify the concentrations of phthalates in 11 soil samples from different regions of China. The contents of DEP, DBP and DEHP in soils were ranged 0-0.42, 0-1.43, and 0.24-2.35 mg/kg, respectively, and no DMP and DnOP was detected. The limits of detection for DMP, DEP, DBP, DEHP, and DnOP were found to be 0.050, 0.051, 0.052, 0.054, and 0.063 mg/kg, respectively. The results obtained by the MEKC method were compared with those obtained by gas chromatography with flame ionization detector (GC-FID), and a good agreement was achieved.

Acetonitriles↗

PubMed2005

Non-aqueous capillary electrophoresis for separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its medicinal preparations.

A non-aqueous capillary electrophoresis method has been developed for the separation and simultaneous determination of fraxin, esculin and esculetin in Cortex fraxini and its preparation for the first time. Optimum separation of the analytes was obtained on a 47 cm x 75 microm i.d. fused-silica capillary using a non-aqueous buffer system of 60 mM sodium cholate, 20 mM ammonium acetate, 20% acetonitrile and 3% acetic acid at 20 kV and 292 K, respectively. The relative standard deviations (RSDs) of the migration times and the peak heights of the three analytes were in the range of 0.23-0.28 and 2.12-2.60%, respectively. Detection limits of fraxin, esculin and esculetin were 0.1557, 0.4073 and 0.5382 microg/mL, respectively. In the tested concentration range, good linear relationships (correlation coefficients 0.9995 for fraxin, 0.9999 for esculin and 0.9992 for esculetin) between peak heights and concentrations of the analytes were observed. This method has been successfully applied to simultaneous determination of the three bioactive components with the recoveries from 90.2 to 109.2% in the five samples.

Acetates↗

PubMed2005

Nanoparticle formulation may affect the stabilization of an antiischemic prodrug.

The prodrug 5'-octanoyl-CPA (Oct-CPA) of the antiischemic N6-cyclopentyladenosine (CPA) has been encapsulated by nanoprecipitation in poly(lactic acid) nanoparticles, which have been recovered by gel-filtration, ultra-centrifugation or dialysis. We have analysed how different surfactants and purification methods can influence the nanoparticle characteristics. The particle sizes have been obtained by scanning electron microscope, whereas a SdFFF system was employed to detect their distributions. The Oct-CPA release from nanoparticles and stabilities in human blood of free and encapsulated prodrug have been analysed by HPLC techniques. The effects of nanoparticles on CPA interaction toward adenosine A1 receptor (its action site) have been analysed using radiolabelled drugs. The smallest nanoparticles and the best degree of homogeneity have been obtained using sodium cholate; the best recovery has been achieved by dialysis, whereas gel-filtration and ultra-centrifugation have induced the greatest removal of surfactants. The release of Oct-CPA was better controlled from the nanoparticles obtained using Pluronic F68 and purified by gel-filtration or ultra-centrifugation. Similarly, these nanoparticles better increased the stability of the prodrug in human blood. In particular, the nanoparticles purified by ultra-centrifugation induced a strong stability to a fraction of the encapsulated Oct-CPA. Any interference by unloaded nanoparticles has been registered for CPA-adenosine A1 receptor interaction.

Adenosine↗

PubMed2001

Enzymatic syntheses of T antigen-containing glycolipid mimicry using the transglycosylation activity of endo-alpha-N-acetylgalactosaminidase.

Thomsen-Friedenreich antigen (T antigen) disaccharide, beta-D-galactose-(1-->3)-alpha-N-acetyl-D-galactosamine (beta-D-Gal-(1-->3)-alpha-D-GalNAc), containing glycolipid mimicry was synthesized using the transglycosylation activity of endo-alpha-N-acetylgalactosaminidase from Bacillus sp. This enzyme could transfer the disaccharide from a p-nitrophenyl substrate to water-soluble 1-alkanols and other alcohols at a transfer ratio of 70% or more. Although the transfer ratios were lower for water-insoluble than water-soluble alcohols, they were shown to increase by adding sodium cholate to the reaction mixtures. The enzyme also transferred the disaccharide directly from asialofetuin to 1-alkanols. The anomeric bond between the disaccharide and 1-alkanols of the transglycosylation product is in the alpha configuration as determined by sequential digestion of jack bean beta-galactosidase and Acremonium alpha-N-acetylgalactosaminidase. Since the transglycosylation product, beta-D-Gal-(1-->3)-alpha-D-GalNAc-(1-->O)-hexyl, efficiently inhibits the binding of anti-T antigen monoclonal antibody to asialofetuin, it has potential as an agent for blocking T antigen-mediated cancer metastasis.

Alcohols↗

PubMed1989

Self-association and solubility behaviors of a novel anticancer agent, brequinar sodium.

To aid in the selection of appropriate excipients to formulate brequinar sodium [6-fluoro-2-(2'-fluoro-1,1'-biphenyl-4-yl)-3-methyl-4-quinolinecarboxyli c acid sodium salt; DuP 785], studies were initiated to characterize thoroughly its solubility behavior. The measured solubilities at RT (approximately 23 degrees C) agreed with the theoretical values in the pH range from 0.5 to 7.2, but became significantly greater than theoretical values at pH values above 7.2. This deviation was likely due to the vertical stacking-type self-association between brequinar molecules in water. The NMR and pH methods determined a critical association concentration of 15 mg/mL. Sodium salicylate, which has been proven to interfere with molecular self-association, reduced drug solubility from 116 to 10 mg/mL. But urea, another deaggregative agent, gave about a twofold increase rather than a decrease in solubility. Addition of sodium chloride caused a 226-fold decrease in solubility. The apparent solubility product did not remain constant but decreased as sodium chloride concentration increased, suggesting that the added salt decreased the degree of self-association between brequinar molecules. Among four surfactants examined (a bile salt with a rigid fused ring versus three ordinary surfactants with a flexible chain structure), only sodium cholate significantly increased the aqueous solubility of brequinar sodium.

Antineoplastic Agents↗

PubMed1984

Characterization of cholate-solubilized dopamine receptors from human, dog and rat brain.

[3H]Spiperone binding sites were solubilized in high yield from human, dog and rat brain with a mixture of sodium cholate (0.3% w/v) and sodium chloride (1.4 M). The binding sites were not sedimented after one hour at 100,000 g, they passed freely through 0.20 micron filters, migrated as a single peak in gradient sedimentation and were retarded upon gel filtration, proving that they were truly solubilized. The solubilized binding sites were definitely of dopaminergic nature. They showed saturable, reversible, high affinity binding of [3H]spiperone; displacement of [3H]spiperone binding by nanomolar concentrations of dopamine antagonists and micromolar concentrations of serotonin antagonists; stereo-specificity and a good correlation with drug affinities for membrane preparations. The non-displaceable, non-specific [3H]spiperone binding was very low. Gradient sedimentation analysis revealed a sedimentation coefficient of 12 S for dog solubilized preparations, 9 S for rat solubilized preparations and only 2.5 S for human solubilized preparations (values, uncorrected for detergent binding). Gel filtration experiments seem to confirm these molecular characteristics. Therefore the present results show that the dopamine receptor reveals the same pharmacological properties when solubilized with cholate-salt from rat, dog or human brain, while physico-chemical properties seem to indicate some differences.

Animals↗

PubMed1995

Separation of estrogens by micellar electrokinetic chromatography.

Capillary electrophoresis of the sex hormone estrogens using different buffer components was investigated. Free zone electrophoresis with 10 mM phosphate buffer (pH 11.5) or 10 mM phosphate buffer with 10-20% methanol was not effective in separating the ten estrogens used in this study. However, nine estrogens were resolved by micellar electrokinetic chromatography using a 10 mM borate buffer (pH 9.2) containing 100 mM sodium cholate. In addition, some estrogens were partially separated using sodium dodecyl sulfate (SDS) micellar buffers; however, the addition of modifiers such as organic solvents or cyclodextrins improved resolutions significantly. Using a 10 mM phosphate buffer (pH 7.0) containing 50 mM SDS and 20% methanol, or a 10 mM borate buffer (pH 9.2) containing 50 mM SDS and 20 mM gamma-cyclodextrin, all ten of the tested estrogens were separated. However, the cyclodextrin-modified buffer allowed faster separation.

Chromatography, Liquid↗