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PubMed1995

Increasing development of pepsinogen-altered pyloric glands and adenocarcinoma in glandular stomach of analbuminemic rats.

The susceptibility of pepsinogen-altered pyloric glands (PAPG) and neoplastic glandular stomach lesions induced by N-methyl-N-nitro-N-nitrosoguanidine (MNNG) and catechol or sodium cholate in Nagase analbuminemic rats (NAR) was compared to Sprague-Dawley rats (SD). Male NAR and SD rats were given a single dose of 80 mg/kg body weight of MNNG by gastric intubation and, 2 weeks later, fed basal diet containing 0.8% catechol or 0.3% sodium cholate for 18 weeks. The animals were killed at the end of week 20 or after maintenance on basal diet at week 60. The number of pepsinogen-altered pyloric glands at week 20 was significantly (P < 0.001) higher in NAR fed either catechol or sodium cholate compared with SD rats. At week 60, adenomatous hyperplasias and adenocarcinomas were observed in 7 (88%; P < 0.01) and 3 (38%; P < 0.01) of 8 NAR fed catechol and in 4 (22%) and 0 of 18 SD rats, respectively. The results show that the frequency of PAPG in NAR and SD rats is related to the susceptibility to glandular stomach carcinoma. PAPG is a useful endpoint lesion for evaluation of gastric carcinogenicity in a 20-week carcinogenicity test, and NAR are sensitive for glandular stomach carcinogenesis.

Adenocarcinoma↗

PubMed2004

The dominant role of solvent in the sequestering of bile salts by hydrophobic cationic polymeric resins.

The binding behavior of sodium cholate, a trihydroxy hydrophobic bile salt, by a polyacrylamide resin with N,N,N-trimethylammonium dodecyl chloride (QPDA12) pendant group was determined with varying buffer conditions and in the presence of 1,2-propanediol as a solvent perturbant. Binding constants extracted from the fit of the binding isotherms to the Langmuir equation were obtained at several temperatures. The temperature dependence of the binding behavior indicated that binding, in comparison with that of the dihydroxy chenodeoxycholate, was weaker due to a smaller positive entropic change, despite a lowered enthalpic barrier. Enthalpy-entropy compensation with a compensation temperature of 285-290 K, characteristic of processes involving water, was found to encompass both the cholate and chenodeoxycholate data under a wide variety of conditions. Previous studies with sodium chenodeoxycholate determined that loss of hydrophobic hydration within the resin dominated the thermodynamics of the binding process, but the observations with sodium cholate revealed that solvent liberation about the bile salt is also a contributor.

Acrylic Resins↗

PubMed1976

Characterization of the recombination reaction of rhodopsin.

The kinetics of recombination of 11-cis-retinal with bleached rod outer segments and sodium cholate solubilized rhodopsin have been investigated. At neutral pH, it was found that bleached rod outer segments in the presence of an excess of 11-cis-retinal follow pseudo-first-order kinetics. The results suggest the second-order formation of an intermediate addition compound followed by a first-order dehydration step to form a protonated aldimine linkage. In addition, at pH values above 7.5 or below 6.5 the kinetics of recombination are complex, indicating the formation of a molecular species inactive in recombination which is in equilibrium with the active form of opsin. Based upon the observed rate constants as a function of pH, a scheme is presented to describe the recombination reaction in bleached rod outer segments. The kinetics of recombination of sodium cholate solubilized opsin were also analyzed. In terms of formation of an intermediate addition compound and subsequent dehydration, the values for the individual rate constants for both bleached rod outer segments and cholate-solubilized opsin were found to compare very favorably. These results demonstrate that the sodium cholate (2 mg/ml) maintains opsin in a conformation very similar to that in the rod outer segment membrane and suggest that the cholate-opsin complex is an excellent model system for studies on opsin-membrane interactions.

Animals↗

PubMed2003

High-cholesterol diets induce changes in lipid composition of rat erythrocyte membrane including decrease in cholesterol, increase in alpha-tocopherol and changes in fatty acids of phospholipids.

Effects of high dietary cholesterol on erythrocyte membrane lipids were studied. Feeding rats with a diet containing 0.5% cholesterol and 0.15% sodium cholate for two weeks induced changes in erythrocyte membrane lipids including a decrease in cholesterol, an increase in alpha-tocopherol (alpha-Toc) and changes in the fatty acid composition of phospholipids. Oleic acid and linoleic acid increased, while arachidonic acid decreased in phosphatidylcholine. Saturated fatty acids decreased and unsaturated fatty acids increased in phosphatidylethanolamine. Almost the same changes in membrane lipids were also noted after six weeks of feeding rats with the diet. A diet containing 0.5% cholesterol but without sodium cholate caused a decrease in erythrocyte cholesterol and an increase in erythrocyte alpha-Toc after two weeks of feeding, as compared to the basal diet, indicating that high dietary cholesterol, but not sodium cholate, was responsible for these changes in the erythrocyte membrane.

Animals↗

PubMed1987

The effect of detergents on bovine cytochrome c oxidase: a kinetic approach.

(1) Investigation of the relationship between the detergent concentration and steady-state and pre-steady-state kinetics of cytochrome c oxidase proved to be a valid approach in the study of protein-detergent interaction. (2) Laurylmaltoside, sodium cholate and Triton X-100 influenced the kinetics of cytochrome c oxidase cooperatively at detergent concentrations near their critical micelle concentration. This mode of interaction reflects disaggregation of the oxidase as a result of cooperative binding of the detergent. (3) Addition of increasing concentrations of Tween-80 to the aggregated enzyme caused a more gradual decrease in aggregation of the oxidase, which did not result in a change in activity of the enzyme. This suggests that aggregation of cytochrome c oxidase occurs in a highly regular manner in which no catalytic sites are shielded off. (4) Oxidase aggregates present at detergent concentrations below the critical micelle concentration of laurylmaltoside and Triton X-100 showed considerable activity. Their kinetics were equal to those of the oxidase in Tween-80, suggesting that the protein molecules are aligned in a similar way in all oligomers. Aggregates present in low concentrations of sodium cholate showed turnover rates that were twice as low as those observed with other aggregates. (5) Solubilisation of the oxidase by sodium cholate or Triton X-100 resulted in almost complete inhibition of enzymic activity, whereas the association rate of ferrocytochrome c was almost equal to that found for monomeric oxidase in laurylmaltoside. These results are in agreement with a mixed-type inhibition.

Animals↗

PubMed2006

Individual dissolution of single-walled carbon nanotubes in aqueous solutions of steroid or sugar compounds and their Raman and near-IR spectral properties.

The individual solubilization of single-walled carbon nanotubes (SWNTs), achieved by using ten different anionic-, zwitterionic-, and nonionic-steroid biosurfactants and three different sugar biosurfactants, was examined. Aqueous micelles of anionic cholate analogues, such as sodium cholate (SC), sodium deoxycholate (SDC), sodium taurocholate (STC), sodium taurodeoxycholate (STDC), sodium glycocholate (SGC), as well as N,N-bis(3-D-gluconamidopropyl)cholamide (BIGCHAP) and N,N-bis(3-D-gluconamidopropyl)deoxycholamide (deoxy-BIGCHAP), exhibited good abilities to dissolve the SWNTs individually. Aqueous micelles of nonionic biosurfactants, such as sucrose monocholate (SMC), n-octyl-beta-D-glucoside (OG), n-decyl-beta-D-maltoside (DM), and n-decanoyl-N-methylglucamide (MEGA-10), could dissolve the SWNTs, however, the solubilization abilities were weaker than those of the anionic cholate analogues. In sharp contrast, the solubilization abilities of the zwitterionic micelles of 3-[(3-cholamidopropyl)dimethylammonio]propanesulfonic acid (CHAPS) and 3-[(3-cholamidopropyl)dimethylammonio]-2-hydroxypropanesulfonic acid (CHAPSO) were very low, and almost zero for OG. It is evident that the chemical structures, in particular the substituent groups of the surfactants, play an important role in the solubilization of SWNTs. The near-IR photoluminescence behaviors of the SWNTs dissolved in aqueous micelles and in 1 mM biosurfactants were investigated. The chirality indices of the SWNTs dissolved in these solutions depend on the chemical structures of the biosurfactants. The Raman spectra of the SWNTs dissolved in a 1 mM solution of SC suggest the selective extraction of the metallic SWNTs. Finally, a possible solubilization mechanism using steroid surfactants is described. The SWNTs dissolved individually in water-containing biocompounds are useful in many areas of nano- and materials chemistry.

Journal Article↗

PubMed1981

Stabilization of acetylcholine receptor channels by lipids in cholate solution and during reconstitution in vesicles.

Acetylcholine receptors were solubilized from electric organ membranes of Torpedo californica in mixed micelles of sodium cholate and soybean lipids. Sodium cholate, when supplemented with relatively low amounts of soybean lipids (cholate:lipid, 20:1, molar ratio), was effective in solubilizing receptors without denaturing their agonist-regulated cation channels. Another dialyzable detergent, octylglucoside, denatured the ion channel even in the presence of excess lipids. Reassembly of receptors and lipids into vesicles was achieved by cholate dialysis. About 70% of the receptors were oriented with their toxin binding sites on the external surface of the vesicles. Evidence suggests that all of the receptors in a single vesicle were oriented either right side out or inside out. During the reassembly process about 10-fold greater lipid concentrations were required for the preservation of channel function. At lipid/protein ratios greater than 16:1 (w/w), receptors reassembled into vesicles at a constant protein/lipid ratio. These vesicles contained approximately 7% receptors by weight, 5-fold less than the native membrane. The remainder of the lipid assembled into small vesicles which did not contain receptors. At lipid/protein ratios less than 16:1 (w/w), receptors reassociated with lipids in higher weight ratios. Irreversible inactivation of a fraction of the acetylcholine receptor channels occurred in proportion to the greater packing density. This channel denaturation was accompanied by a lowered susceptibility of the disulfide bond between the delta subunits of the acetylcholine receptor dimer to reducing agents. Toxin binding and the orientation of the receptors in the reconstituted vesicles was not affected by reduced lipid/protein ratios. The unexpected constant acetylcholine receptor/lipid ratio in the reconstituted vesicles and the unexpected uniform orientation of the acetylcholine receptors within a vesicle are discussed in terms of the interactions occurring during the initial nucleation events of the reassembly process.

Acetylcholine↗

PubMed1996

Local dynamics of the M13 major coat protein in different membrane-mimicking systems.

The local environment of the transmembrane and C-terminal domain of M13 major coat protein was probed by site-directed ESR spin labeling when the protein was introduced into three membrane-mimicking systems, DOPC vesicles, sodium cholate micelles, and SDS micelles. For this purpose, we have inserted unique cysteine residues at specific positions in the transmembrane and C-terminal region, using site-directed mutagenesis. Seven viable mutants with reasonable yield were harvested: A25C, V31C, T36C, G38C, T46C, A49C, and S50C. The mutant coat proteins were indistinguishable from wild type M13 coat protein with respect to their conformational and aggregational properties. The ESR data suggest that the amino acid positions 25 and 46 of the coat protein in DOPC vesicles are located close to the membrane-water interface. In this way the lysines at positions 40, 43, and 44 and the phenylalanines at positions 42 and 45 act as hydrophilic and hydrophobic anchors, respectively. The ESR spectra of site specific maleimido spin-labeled mutant coat proteins reconstituted into DOPC vesicles and solubilized in sodium cholate or SDS indicate that the local dynamics of the major coat protein is significantly affected by its structural environment (micellar vs bilayer), location (aqueous vs hydrophobic), and lipid/protein ratio. The detergents SDS and sodium cholate sufficiently well solubilize the major coat protein and largely retain its secondary structure elements. However, the results indicate that they have a poorly defined protein-amphiphilic structure and lipid-water interface as compared to bilayers and thus are not a good substitute for lipid bilayers in biophysical studies.

Capsid↗

PubMedDate not supplied

The influence of the ionic medium on the behaviour of sodium glycocholate and cholate aqueous solutions.

In the framework of research on the sodium bile salts, solutions of sodium cholate and glycocholate had been studied only at three ionic medium concentrations. In this paper, experiments in two other concentrations of ionic medium are carried out both to verify the behaviour dependence on the ionic medium and to apply the results of this paper to a future investigation on solutions containing contemporary sodium cholate and glycocholate. To this aim, solubility, protonation constants, lead (II) salts solubility products at 25 degrees C and in 0.300 and 0.750 mol dm(-3) N(CH3)4Cl were determined. The formed species in solutions containing lead (II) together with the selected bile salts and the behaviour of the sodium salts in micellar and premicellar solutions were investigated, too. The obtained results were compared with those obtained at the other ionic medium concentrations.

Glycocholic Acid↗

PubMed1987

Functional reconstitution of the integral membrane proteins of influenza virus into phospholipid liposomes.

The integral membrane proteins of influenza virus, a hemagglutinin and a neuraminidase, have been incorporated into liposomes composed of either phosphatidylcholine or a mixture of phosphatidylcholine and phosphatidylethanolamine (2:1 w/w) using detergent dialysis. The virus spike glycoproteins for reconstitution were selectively solubilized by using cetyltrimethylammonium bromide to leave a "core particle", which lacked a lipid bilayer but possessed quaternary structure as observed by electron microscopy. The viral spike proteins were combined with exogenous phospholipid in excess sodium cholate followed by exhaustive dialysis for 150 h. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that only the viral glycoproteins were associated with all the complexes formed. The level of sodium cholate remaining after dialysis was shown to be reduced to less than 1 molecule per 80 protein molecules. Viral proteins reconstituted into dimyristoylphosphatidylcholine liposomes were shown to have retained hemagglutination, low-pH-dependent hemolysis, and neuraminidase activities and were associated with a lipid bilayer in two types of complexes with average lipid to protein mole ratios after sucrose density gradient purification of either 590:1 or 970:1. The bilayer vesicles formed were of similar sizes and were shown by negative-stain electron microscopy to be 150-300 nm in diameter with well-defined spikes on their surface. Reconstituted liposomes of dimyristoylphosphatidylcholine were found to be unstable with respect to their trapped volume and therefore were unsuitable for fusion studies, unlike complexes formed with phosphatidylcholine or a mixture of phosphatidylcholine/phosphatidylethanolamine derived from hen eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Dimyristoylphosphatidylcholine↗

PubMedDate not supplied

Detergent solubilization of liver microsomal acyl-coenzyme A:1-acyl-glycerophosphocholine acyltransferase in nephrotic rat.

Hyperlipidaemia is a common feature of nephrotic syndrome and this has been thought to involve increased assembly and secretion of very low density lipoprotein (VLDL) in the liver. An important pathway for an indirect modulation of VLDL. Synthesis is the reaction catalyzed by the acyl-coenzyme A:1-acyl-glycero-phosphcholine acyl transferase. We therefore investigated the activity of this enzyme in liver microsomes isolated from puromycin amino nucleoside induced nephrotic rats. When oleoyl-CoA was employed as the acyl-donor, our results indicated that both the total and detergent soluble enzyme activities (112.2 +/- 16.7; 116.1 +/- 17.5 units, respectively) were significantly higher than the corresponding control levels of 91.1 +/- 11.1 and 75.4 +/- 20.9 units respectively. The percentage stimulation by sodium cholate were 176.5 and 192.2 for the control and nephrotic rats, respectively. In absence of sodium cholate, when oleoyl CoA was replaced by arachidonoyl-CoA as acyl-donor, the measured total enzyme activity was only significantly reduced in the control rats (71.1 +/- 8.9 Vs 91.1 +/- 11.1 Units). Oleoyl-CoA as acyl-donor gave higher values for the soluble and residual enzyme activities (90.4 13.3; 99.5 34.5 unit) than the corresponding control levels (75.9 +/- 10.0; 50.5 +/- 34.0 units) as compared to arachidonoyl-CoA. In the control group the difference was only significant in the residual activity (92.9 20.5 Vs 64.7 24.1 units). The addition of monomethylethanomine (200 mM) had little or no effect, while both reduced glutathione (10 mM) and 1,2-diacylglycerol (1 mM) caused significant reduction in measured activity. These results indicated that in nephrotic rats new phospholipid synthesis is enhanced and this could contribute to the increased VLDL assembly and secretion usually associated with nephrotic syndrome.

1-Acylglycerophosphocholine O-Acyltransferase↗

PubMed1989

28 kDa adenosine-binding proteins of brain and other tissues.

Membranes prepared from calf brain were solubilized and chromatographed on a column containing 5'-amino-5'-deoxyadenosine covalently linked to agarose through the 5'-amino group. When the column was eluted with adenosine, a pure protein emerged with subunit molecular mass of 28 kDa. The protein was extracted from the membranes with sodium cholate, but not with 100 microM-adenosine or 0.5 M-NaCl. A similar 28 kDa protein was isolated from the soluble fraction of calf brain. The yield of membrane-bound and soluble 28 kDa protein per gram of tissue was about the same. The 28 kDa protein was also found in membrane and soluble fractions of rabbit heart, rat liver and vascular smooth muscle from calf aorta. The yield per gram of tissue fell into the order brain greater than heart approximately vascular smooth muscle greater than liver for the 28 kDa protein from the membrane fraction, and brain approximately heart greater than vascular smooth muscle greater than liver for the 28 kDa protein from the soluble fraction. Polyclonal antibodies to pure 28 kDa protein from calf brain membranes cross-reacted with the 28 kDa protein from calf brain soluble fraction and with 28 kDa proteins isolated from other tissues. The 28 kDa protein from calf brain membranes was also eluted from the affinity column by AMP and 2',5'-dideoxyadenosine, but at a concentration higher than that at which adenosine eluted the protein, but N6-(R-phenylisopropyl)adenosine, 5'-N-ethylcarboxamidoadenosine, ADP, ATP, GTP, NAD+, cyclic AMP and inosine failed to elute the protein at concentrations up to 1 mM. The 28 kDa protein from the soluble fraction was not eluted by 3 mM-AMP or 1 mM-N6-(R-phenylisopropyl)adenosine,-5'-N-ethylcarboxamidoadenosine or -cyclic AMP. Unexpectedly, the soluble 28 kDa protein was eluted by AMP in the presence of sodium cholate. Soluble 28 kDa protein from calf brain had a KD for adenosine of 12 microM. Membrane 28 kDa protein from calf brain had a KD of 14 microM in the presence of 0.1% sodium cholate. Amino acid compositions of the 28 kDa proteins were similar, but not identical.

Adenosine↗

PubMed2006

Rapid-onset intranasal delivery of metoclopramide hydrochloride Part II: Safety of various absorption enhancers and pharmacokinetic evaluation.

In the present study, several nasal absorption enhancers, used in metoclopramide hydrochloride (MCP HCl) nasal solutions, have been screened for their possible damaging effect in the in vitro human erythrocytes lysis experiment. Moreover, the in vivo leaching of biological markers from the rat nasal epithelium was used as a quantitative assessment for possible nasal mucosal irritation whereby the extent of release of total protein and lactate dehydrogenase (LDH) in the nasal lavage fluid was determined. Results showed that insignificant hemolysis from normal saline (P<0.05) occurred with the enhancer protamine sulphate while poly-l-arginine and sodium cholate demonstrated very low (<15%) hemolysis and caused insignificant protein and LDH release from the rat nasal mucosa. Conversely, sodium deoxycholate and chitosan polymers (either of low or high molecular weight) showed high (>60%) hemolysis in vitro and the release of the biological markers in vivo was significantly higher (P<0.05) than the control solution (no enhancer). A significant correlation (P<0.05) existed between the enhancement effect of MCP HCl nasal absorption and the amounts of protein (r=0.85) and LDH (r=0.88). Furthermore, the pharmacokinetics of MCP HCl was determined after intravenous (IV), per-oral and intranasal administration of 10mg drug dose in rabbits. The application of a nasal spray (NS) solution containing 0.5% sodium cholate resulted in a significant improvement (P<0.05) in both the rate and extent of absorption of MCP HCl where the T(max) achieved was 23.3min as compared to 50min in case of the oral solution while the area under the serum concentration-time curve (AUC(0-infinity)) were 506.1, 434.9 and 278.7microg/mlmin for IV, NS and oral solutions, respectively. These values corresponded to absolute bioavailabilities of 87.21 and 55.61% for the NS and oral solutions, respectively. It could thus be concluded that NS of MCP HCl represents a viable approach to achieving rapid and high systemic drug absorption during the emergency treatment of severe emesis.

Absorption↗

PubMed1979

Human leucocyte cerebroside sulphate sulphatase.

Some of the properties of the cerebroside sulphate sulphatase of human leucocyte extracts have been studied. The enzyme has an apparent KM of 2.9 mmol/l and is inhibited by the products of the reaction, sulphate and galactocerebroside. A number of divalent metal ions including manganese and magnesium stimulated the reaction only slightly at 5 mmol/l but inhibited strongly at 20 mmol/l. Triton X-100 present in leucocyte extracts also inhibited, increasing both the apparent KM and Vmax. The enzyme activity was dependent on the presence of anionic detergents. At low substrate concentrations a crude taurocholate preparation was the most active of all bile acids examined. Pure taurocholate and sodium cholate were considerably less active. At highter substrate concentrations however, sodium cholate produced the greatest stimulation of enzyme activity. These data suggest that the bile acid/substrate ratio may be a critical factor in determining cerebroside sulphate sulphatase activity at different substrate concentrations.

Cerebroside-Sulfatase↗

PubMed1976

Side chain hydroxylations in biosynthesis of cholic acid. 25- and 26-Hydroxylation of 5beta-cholestane-3alpha, 7alpha, 12alpha-triol by reconstituted systems from rat liver microsomes.

25- and 26-Hydroxylation of 5beta-cholestane-3alpha, 7alpha, 12alpha-triol was studied with reconstituted systems from rat liver microsomes consisting of partially purified cytochrome P -450, NADPH-cytochrome P -450 reductase, a phospholipid, and an NADPH -generating system. Cytochrome P -450 was prepared either by sodium cholate treatment and ammonium sulfate fractionation or by subtilisin and sodium deoxycholate treatment followed by DEAE-cellulose chromatography. No side chain hydroxylation was observed when cytochrome P-450 was omitted. With ammonium sulfate-fractionated cytochrome P-450 25- and 26-hydroxylation was stimulated 5- to 8-fold by addition of NADPH-cytochrome P-450 reductase. With subtilisin-treated cytochrome P-450 an almost absolute requirement for NADPH-cytochrome P-450 reductase was observed. Omission of lipid did not reduce the rate of hydroxylation. Centrifugation of the cytochrome P-450 preparation at 100,000 X g for 1 hour just before incubation increased markedly lipid dependency. A significant difference between 25- and 26-hydroxylation was observed with respect to substrate saturation. The stimulatory effect of phenobarbital treatment on 25-hydroxylation and the inhibitory effect of this treatment on 26-hydroxylation were associated with the cytochrome P-450 fraction. The use of increasing amounts of sodium cholate in the solubilization of cytochrome P -450 resulted in a gradual decrease of 25-hydroxylase activity and a gradual increase of 26-hydroxylase activity. 25- and 26-Hydroxylase activities were separated partially by chromatography of subtilisintreated cytochrome P-450 fraction on DEAE-cellulose. The question whether different species of cytochrome P-450 are involved in 25- and 26-hydroxylation is discussed.

Animals↗

PubMed2004

In vitro and in vivo transfection efficiency of a novel ultradeformable cationic liposome.

Cationic lipids have been often used as one of the major components in making most promising non-viral gene delivery systems, whereas sodium cholate, a surfactant so-called edge activator has been used in preparing ultradeformable and ultraflexible liposomes called Transfersomes. Using both a cationic lipid, DOTAP and sodium cholate, a novel formulation of ultradeformable cationic liposome (UCL) has been prepared. The average particle size of this formulation was approximately 80 nm. The physical and chemical stabilities at two different temperatures (4 degrees C and 20 degrees C) were also evaluated for 60 days. The ultradeformability of new formulation was also assessed, and it has been proved that the formulation is deformable. In vitro transfection efficiency of plasmid DNA/UCL was assessed by the expression of green fluorescent protein (GFP) in four cell lines, OVCAR-3 (human ovarian carcinoma cells), HepG2 (human hepatoma cells), H-1299 (human lung carcinoma cells) and T98G (human brain carcinoma cells). The optimal ratio of DNA to liposome for maximal transfection efficiency was 1:14 (w/w) in all the cell lines except for the human brain carcinoma cells. The same formulation was tested for in vivo transfection efficiency and its retention time within the organs by applying the DNA/UCL complexes on hair-removed dorsal skin of mice non-invasively. It was found that genes were transported into several organs for 6 days once applied on intact skin.

DNA↗

PubMed1993

Resolution of phospholipid molecular species by 31P NMR.

Phosphorus-31 NMR chemical shifts of phospholipids (PLs) solubilized in bile salts were studied with respect to variations in the structure of the acyl substituents. The presence of double bonds in the acyl chains of phosphatidylcholine (PC), phosphatidylethanolamine (PE), phosphatidylglycerol (PG), and phosphatidic acid (PA) induced small but consistent upfield shifts relative to the corresponding disaturated acyl PL signals. The magnitudes of the unsaturation-related upfield shifts were approximately twice as large in sodium cholate as in sodium deoxycholate. Chemical shift separations of PC, PE, and PG dipalmitoyl-dioleoyl species pairs increased slightly at lower temperatures. Resolution of the PC species pair was maximized and nearly independent of cholate-to-PL ratio at values greater than about 100 in 2% cholate. Only the PA species resolution varied significantly over the pH range 6.5 to 9.5, in the vicinity of its pK2. Shift differences for a homologous series of disaturated acyl PCs showed a logarithmic dependence on chain length. Spectra for a variety of PC standards were used to interpret the composite PC signals from egg yolk extract, soybean extract and whole human amniotic fluid. The 31P NMR analyses were consistent with published chromatographic studies. Interpretation of composite PL signals in the cholate system is simplified for mixtures having restricted acyl chain length and degree of unsaturation.

Amniotic Fluid↗

PubMedDate not supplied

Isolation and characterization of cytochrome b5 from Candida tropicalis grown on alkane.

Cytochrome b5 from Candida tropicalis grown on alkane has been solubulized in three different ways (sodium cholate, trypsin, osmotic wash). After solubilization of the microsomal membrane with sodium cholate, the purification of cytochrome b5 was achieved by DEAE-cellulose chromatography, hydroxylapatite chromatography, a second DEAE-cellulose chromatography and a Sephadex G-75 gel filtration. The purified protein had an apparent molecular weight of 16 000 +/- 1 000. After solubilization by trypsin treatment or osmotic wash, the purification procedure yielded a protein with an apparent molecular weight of 12 000 +/- 1 000. Though the purified proteins presented molecular weights depending on the technique of solubilization, they exhibited identical optical properties, a great stability with respect to temperature and pH, and were all autooxidable. Redox titrations revealed differences in their midpoint potential values, which were 35 +/- 5 mV for the b5 purified after cholate solubilization, -59 +/- 5 mV for the b5 purified after trypsin treatment and -65 +/- 5 mV for the b5 purified after osmotic wash.

Alkanes↗