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Query: CAS:22373-09-7 (cholestane)
 779 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The effect of asymmetric phospholipids, such as platelet-activating factor (PAF), lyso-PAF and lysophosphatidylcholine, on phosphatidylcholine bilayers has been examined using ESR, 31P-NMR and X-ray diffraction methods. ESR and 31P-NMR experiments have been performed on oriented multibilayers. ESR measurements of 5-doxyl stearic acid, as a spin probe, show that PAF disorients phosphatidylcholine bilayers when present at molar ratios greater than 40%. This is manifest as a broadening of the local director orientation distribution, a parameter required to simulate the lineshape. Despite the marked change of the regular in-plane orientation of the films, there are only slight changes in the order parameter of the acyl chains. Cholesterol orients films containing asymmetric phospholipids, in a way consistent with the formation of 1/1 stoichiometric complexes between cholesterol and the asymmetric phospholipid. Such complexes can be detected with 3-doxyl cholestane, a spin-labelled sterol analogue interacting with lyso-PAF and PAF. Simulations of 31P-NMR resonance linewidth of oriented multibilayers of PAF/egg lecithin mixtures indicate a rippled structure which accounts for the perturbed distribution of the local director observed by ESR spin probe measurements. Micellisation of the film can be discounted on the basis of the 31P-NMR linewideth for the concentration range investigated. X-ray diffraction studies of liposomes of dimyristoyl- and dioleoyl-phosphatidylcholine containing PAF relate the disorientation of the film with the emergence of a lamellar interdigitated phase of reduced (4.2 nm) repeat distance. This interdigitated phase coexists with the lecithin lamellar phase (repeat spacing 6.0 nm) at temperatures below and above the gel-to-liquid crystal transition temperature of the lecithin. Cholesterol/PAF mixtures give X-ray diffraction patterns indexing a lamellar repeat distance of 6.7 nm. Cholesterol also prevents formation of interdigiatated lamellae with the various asymmetric phospholipids. A model is proposed where the asymmetric phospholipid segregates from lecithin to form 'blister-like' structures within the film consisting of thin interdigitated lamellae. Formation of complexes between cholesterol and the asymmetric lipid prevents the creation of these structures.
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PMID:Effects of platelet-activating factor (PAF), lyso-PAF and lysophosphatidylcholine on phosphatidylcholine bilayers, an ESR, 31P-NMR and X-ray diffraction study. 166 4

Attempts were made to elucidate the structure of the toxin isolated from the bile of carp Cyprinus carpio, which is possibly responsible for carp poisoning. By fast atom bombardment (FAB) mass spectrometry, along with 1H- and 13C-NMR, a molecular formula of C27H48O8S containing a sulfate ester group was deduced. Those and other analytical data allowed us to conclude the structure of carp toxin to be 5 alpha-cholestane-3 alpha, 7 alpha, 12 alpha, 26, 27-pentol 26-sulfate, which agreed essentially with that of 5 alpha-cyprinol, an alcohol specific to carp bile, in which the sulfate ester at the C-26 position is lacking.
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PMID:Structure of the toxin isolated from carp (Cyprinus carpio) bile. 226 Jan 4

Starting from cholesterol a simple and efficient synthesis of 5 alpha-cholestane-3,6-dione and 5 beta-cholestane-3,6-dione is described. The 13C shielding data of C-7, C-9, and C-19 in both isomers can be used in the determination of the stereochemistry at C-5 of these compounds. The combination of 13C NMR spectroscopy and the simple synthesis of both isomers offers good opportunities for the determination of the stereochemistry at C-5 of 3,6-dioxosteroids.
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PMID:Synthesis and 13C-NMR analysis of 5 alpha- and 5 beta-cholestane-3,6-dione. 258 7

The nature of bile alcohols and bile acids in gall-bladder and hepatic bile from perfused livers of the small skate (Raja erinacea) has been investigated. The main bile alcohol sulfate was isolated by thin-layer chromatography and analyzed by fast atom bombardment mass spectrometry and 13C NMR. Following solvolysis and purification on Lipidex-DEAP, the bile alcohol profile was measured by capillary gas-liquid chromatography-electron impact mass spectrometry. Based on these studies and on comparison with authentic scymmnol sulfate and scymnol, the main bile alcohol was identified as 5 beta-cholestane-3 alpha,7 alpha,12 alpha,24 xi,26,27-hexol sulfate. The mean +/- SD concentration in gallbladder bile from five different skates was 24.6 +/- 8.7 mmol/l. Only 0.1 mmol/l of cholic acid and its conjugates was found in a pool of skate bile. The main bile alcohol sulfate in the bile of the small skate seems to be a metabolic end product, present in a concentration comparable to that of bile salts in mammals.
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PMID:A bile alcohol sulfate as a major component in the bile of the small skate (Raja erinacea). 272 39

The bile salts present in gallbladder bile of the West Indian manatee, Trichechus manatus latirostris, an herbivorous marine mammal of the tropical and subtropical margins of the Atlantic Ocean, were found to consist of a mixture of bile alcohol sulfates. Bile acids, previously believed to be present in all mammals, were not detected. Using chromatography, mass spectrometry, and 1H- and 13C-nuclear magnetic resonance spectroscopy, the major bile alcohol was identified as 5 beta-cholestane-3 alpha,6 beta,7 alpha-25,26-pentol; that is, it had the nuclear structure of alpha-muricholic acid and the side chain structure of bufol. This compound has not been described previously and the trivial name "alpha-trichechol" is proposed. The second most abundant compound was 5 beta-cholestane-3 alpha,7 alpha,25,26-tetrol. Other bile alcohols were tentatively identified as 5 beta-cholestane-3 alpha,6 beta,7 beta,25,26-pentol (named beta-trichechol), 3 alpha,6 alpha,7 beta, 25-26-pentol (named omega-trichechol) and 5 beta-cholestane-3 alpha,6 beta,7 alpha,26-tetrol. The 1H and 13C NMR spectra of the four 6,7 epimers of 3,6,7 trihydroxy bile acids are described and discussed. All bile alcohols were present as ester sulfates, the sulfate group being tentatively assigned to the 26-hydroxy group. 12-Hydroxy compounds were not detected. The manatee is the first mammal found to lack bile acids, presumably because it lacks the enzymes required for oxidation of the 26-hydroxy group to a carboxylic acid. Trichechols, like other bile salts, are water-soluble end products of cholesterol metabolism; whether they also function as biological surfactants in promoting biliary cholesterol secretion or lipid digestion is unknown.
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PMID:Bile salts of the West Indian manatee, Trichechus manatus latirostris: novel bile alcohol sulfates and absence of bile acids. 339 67

The configuration at C-25 in 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha,25,26-pentol isolated from the bile and feces of patients with cerebrotendinous xanthomtosis (CTX) was determined from the lanthanide-induced circular dichroism (CD) Cotton effects and 13C-NMR measurements. Under anhydrous conditions, CD spectra of 5 beta-cholestane-3 alpha, 7 alpha, 12 alpha,25,26-pentol in the presence of Eu(fod)3 exhibited a large induced negative Cotton effect at 320 nm. On the basis of the empirical rule (primary-tertiary-alpha-diols) in which R compounds have positive Cotton effects and S compounds have negative Cotton effects at 320 nm, it was concluded that 25,26-pentol has the 1,2,glycol structure with C-25 having the S-configuration. This assignment was based upon comparison with model compounds, 25(R and S),26-dihydroxy cholesterols and 25(R and S),26-dihydroxy cholecalciferols whose single-crystal X-ray structure and 13C-NMR studies have been performed. It is suggested that these data may be helpful to clarify the stereospecificity of the hydroxylation of the terminal methyl group of the cholesterol side chain in CTX.
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PMID:Configuration at C-25 in 5 beta-cholestane-3 alpha,7 alpha,12 alpha,25,26-pentol excreted by patients with cerebrotendinous xanthomatosis: circular dichroism and 13C-NMR studies. 355 96

Multiple bilayers of dimyristoyl phosphatidylcholine and potassium oleate were macroscopically oriented between silver-coated glass slides. These model membranes were subjected to an electric field of up to 10(5) V . cm-1. The influence of the field on the molecular structure was monitored by ESR of cholestane and stearic acid spin labels and by NMR of the phosphorus atom in the phosphatidylcholine headgroup. It is concluded that the conformation of the headgroup is greatly affected while no influence on the structure and dynamics of the hydrocarbon chains can be detected. At electric fields above 10(4) V . cm-1, where structural effects are still reversible, spontaneous current fluctuations are observed. At fields above 10(5) V . cm-1, irreversible breakdown of the bilayer structure occurs.
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PMID:Electric field effects on lipid membrane structure. 626 Jan 74

The effect of fatty acids and monoglycerides on barrier properties of liposomal membranes prepared from egg phosphatidylcholine was investigated. The incorporation of these lipids as liposomal membrane components induced the alteration of the permeability to less permeable liposomally entrapped drugs, sulfanilic acid and procainamide ethobromide (PAEB). Monoolein caused greatly increased permeability of both drugs and unsaturated fatty acids markedly enhanced the release rate of PAEB, while saturated fatty acids caused a small increase in the release rate. Electron spin resonance (ESR) investigation with 5-nitroxide stearic acid showed that fatty acids disordered the hydrophobic region of the lipid bilayer and the disordering effect of unsaturated fatty acids was greater than that of saturated ones. It was demonstrated that the incorporated fatty acids and monoglycerides interacted with the polar region of the membranes by ESR study with cholestane label and 1H-NMR study. These results indicated that the increase in the membrane permeability caused by fatty acids and monoglycerides associated with the disorder in the membranes' interior and the interaction of the incorporated lipid with the polar head group of phospholipid.
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PMID:Effect of fatty acids and monoglycerides on permeability of lipid bilayer. 626 5

This paper describes the synthesis of 5 beta-cholestane-3 beta, 7 alpha,25-triol and 5 beta-cholestane-3 beta, 7 alpha, 12 alpha, 25-tetrol from their corresponding 3 alpha-analogs. The method consists of refluxing a mixture of a steroid alcohol, triphenylphosphine, and diethyl azodicarboxylate in benzene solution with an acid such as formic acid. The sterically pure ester (3 beta-formate) so formed after saponification then allows an easy access to the epimer of the starting alcohol. Differentiation of these 3 beta-hydroxy bile alcohols from their corresponding 3 alpha-epimeric analogs was made possible on the basis of proton, 13C-NMR, and mass spectra as well as chromatographic mobility. Steric requirements of sterols and nucleophilicity of attacking acidic components played an important role for the success of this synthesis. Only equatorial hydroxyl groups in these bile alcohols reacted under mild conditions and epimerization, as well as protection of the alcoholic group, was achieved in one step. Formic acid was the acid of choice since the axial formate ester formed is sufficiently reactive to be hydrolyzed (KHCO3/aq X MeOH) under mild conditions.
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PMID:Stereospecific synthesis of 3 beta-hydroxylated bile alcohols. 674 68

A detailed electron spin resonance (ESR) study of mixtures of 1-palmitoyl-2-oleoyl-phosphatidylcholine (POPC) and phosphatidylserine (POPS) in oriented multilayers in the liquid crystalline phase is reported with the purpose of characterizing the effects of headgroup mixing on the structural and dynamical properties of the acyl chains. These studies were performed over a range of blends of POPC and POPS and temperatures, utilizing the spin-labeled lipids 16-phosphatidylcholine and 5-phosphatidylcholine as well as cholestane (CSL). The ESR spectra were analyzed by nonlinear least-squares fitting using detailed spectral simulations. Whereas CSL shows almost no variation in ordering and rotational dynamics versus mole fraction POPS, (i.e. XPS), and 5-PC shows small effects, the weakly ordered end-chain labeled 16-PC shows large relative effects, such that the orientational order parameter, S is at a minimum for XPS = 0.5 where it is about one-third the value observed for XPS = 0 and 1. This is directly reflected in the ESR spectrum as a substantial variation in the hyperfine splitting with XPS. The least-squares analysis also shows a reduction in rotational diffusion coefficient, R perpendicular by a fractor of 2 for XPS = 0.5 and permits the estimation of S2, the ordering parameter representing deviations from cylindrically symmetric alignment. These results are contrasted with 2H NMR studies which were insensitive to effects of mixing headgroups on the acyl chains. The ESR results are consistent with a somewhat increased disorder in the end-chain region as well as a small amount of chain tilting upon mixing POPC and POPS. They demonstrate the high sensitivity of ESR to subtle effects in chain ordering and dynamics.
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PMID:An electron spin resonance study of interactions between phosphatidylcholine and phosphatidylserine in oriented membranes. 806 Dec


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