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PubMed2006

Formation of complex films with water-soluble CTAB molecules.

This communication reports the formation of complex Langmuir monolayer at the air-water interface with the water-soluble N-cetyl N,N,N-trimethyl ammonium bromide (CTAB) molecules when interacted with the stearic acid (SA) molecules. The reaction kinetics of the formation of the CTAB-SA complex was monitored by observing the surface pressure versus time graph. Multilayered LB films of this complex doped with Congo red was successfully formed onto a quartz substrate. UV-Vis absorption and steady-state fluorescence spectroscopic characteristics of this doped LB films confirms the successful incorporation of Congo red molecules in to the CTAB-SA complex films.

Absorption↗
PubMedDate not supplied

Effect of magnesium stearate on chitosan microspheres prepared by an emulsification-coacervation technique.

Chitosan microspheres were prepared using an emulsification-coacervation technique. The w/o emulsion comprised a mixture of light and heavy liquid paraffins containing sodium dioctyl sulphosuccinate as the oil phase and chitosan solution as the aqueous phase. Pentasodium tripolyphosphate was included as a counterion. The chitosan microspheres obtained showed a high degree of aggregation. This was markedly reduced, by the incorporation of magnesium stearate in the disperse phase. The resultant microspheres were then discrete, spherical with smooth surfaces. Additionally, with an increasing magnesium stearate content, larger-sized microspheres were produced. The DSC analysis data suggested that the magnesium stearate was converted to stearic acid during the preparation process. Chitosan microspheres containing propranolol hydrochloride were similarly prepared, but their surface was convoluted and their shape not well defined. Unlike the microspheres without drug, the size of the drug-loaded microspheres decreased with increasing magnesium stearate content. The release of propranolol hydrochloride from the microspheres was fast, irrespective of the content of magnesium stearate. Drug encapsulation efficiency was enhanced when a greater amount of magnesium stearate was used.

Animals↗
PubMed1989

Ontogeny of basolateral membrane lipid composition and fluidity in small intestine.

To evaluate physicochemical properties of the small intestinal basolateral cell surface during postnatal development, membranes were isolated from suckling (14-17 days) and weanling-mature (35-49 days) rabbit jejunal and ileal enterocytes at 30- to 40-fold purification (based on Na+-K+-ATPase specific activity) and with limited contamination from coisolated cellular elements. Membrane lipid analysis demonstrated age-dependent reductions and proximal to distal increases in total lipid (per milligram protein). Postnatal increases in membrane total cholesterol of jejunum (suckling vs. mature, 0.18 vs. 0.26 mumol/mg protein; P less than 0.01) and ileum (0.18 vs. 0.31 mumol/mg protein; P less than 0.01) resulted in markedly higher cholesterol-to-phospholipid molar ratios (jejunum, 0.43 vs. 0.73; ileum, 0.43 vs. 0.72 mumol/mg protein; P less than 0.01). Membranes from mature animals had higher relative sphingomeylin and phosphatidylcholine content and, in both age groups, fatty acyl saturation was increased in ileum compared with jejunum. By utilization of the fluorophores 1,6-diphenyl-1,3,5-hexatriene and DL-12-(9-anthroyl)stearic acid, the fluidity of basolateral membranes and liposomes prepared from extracted membrane lipid decreased markedly in mature rabbits. Arrhenius plots demonstrated higher apparent thermotropic transition temperatures of mature membrane lipid. These data therefore demonstrate significant changes in small intestinal basolateral membrane lipid composition and fluidity that occur during the weaning period. Possible relationships to ontogenesis of membrane protein function are discussed.

Animals↗
PubMed1981

Hydrophobic compounds interfere in radioimmunoassay for basic protein in myelin.

Hydrophobic compounds influenced the accuracy of the radioimmunoassay for myelin basic protein when lipids (stearic acid, phosphatidylcholine, cholesterol, cerebroside, sulfatide, or GM1 ganglioside) or proteolipids (white-matter proteolipid apoprotein, kidney proteolipid apoproteins, or heart proteolipid apoproteins) were added to a known amount of basic protein and the samples assayed. All of these interfere with the assay, but the direction of the error depends on the quantity added: low concentrations of lipid decrease apparent basic protein, high concentrations enhance it. Obviously, results of basic-protein assays must be interpreted carefully.

Animals↗
PubMedDate not supplied

[Effect of butadione on the morphohistochemical changes in the joints in adjuvant polyarthritis].

Prophylactic and therapeutic administration of pyrasol derivatives butadion and stampyrine (antipyrilamide of stearic acid), to rats with adjuvant polyarthritis normalize the structure of the synovial membrane, capsule and of the periarticular tissue of the talocrural articulations, stabilize the proteinic-mucopolysaccharide complexes, lower the permeability of the lysosome membranes and vascular walls and inhibit the phagocystic activity of the histiocytes. Both drugs do not lessen the proliferation of the fibroblasts, but normalize the processes of the collagenogenesis them. The prophylactic and therapeutic effects of stampyrine are superior to those of butadion.

Animals↗
PubMed1985

The structure of bone apatite surfaces.

This is a review of the surface chemistry of bone mineral and its synthetic counterpart hydroxyapatite. Small-angle x-ray scattering and low-temperature nitrogen adsorption measurements show bone mineral surfaces range from 100 to 200 m2/g. The heats of adsorption of small molecules on bone and apatite surfaces show that these materials have polarizing surfaces which form strong bonds with polar and polarizable molecules. Water is hydrogen bonded to these surfaces with energies ranging from 23 Kcal/mol, for low coverage, to 11 Kcal/mol after two full layers; the latter value shows that after two monolayers the water is bonded as strongly to the solution as it is to the apatite surface. Stearic acid in cyclohexane adsorbs on bone and apatite surfaces in a closed-packed manner with the straight-chain molecules in parallel array with the end carboxyl groups hydrogen bonded to surface electronegative ions. Synthetic hydroxyapatite has long been used in chromatography because of the bonding capacity apatite surface has for certain proteins and polynucleotides. The metabolic interplay between bone mineral and the body results from the high magnitude and high reactivity of the mineral surface.

Adsorption↗
PubMed2003

Cocoa and chocolate flavonoids: implications for cardiovascular health.

This paper offers a review of current scientific research regarding the potential cardiovascular health benefits of flavonoids found in cocoa and chocolate. Recent reports indicate that the main flavonoids found in cocoa, flavan-3-ols and their oligomeric derivatives, procyanidins, have a variety of beneficial actions, including antioxidant protection and modulation of vascular homeostasis. These findings are supported by similar research on other flavonoid-rich foods. Other constituents in cocoa and chocolate that may also influence cardiovascular health are briefly reviewed. The lipid content of chocolate is relatively high; however, one third of the lipid in cocoa butter is composed of the fat stearic acid, which exerts a neutral cholesterolemic response in humans. Cocoa and chocolate contribute to trace mineral intake, which is necessary for optimum functioning of all biologic systems and for vascular tone. Thus, multiple components in chocolate, particularly flavonoids, can contribute to the complex interplay of nutrition and health. Applications of this knowledge include recommendations by health professionals to encourage individuals to consume a wide range of phytochemical-rich foods, which can include dark chocolate in moderate amounts.

Anticholesteremic Agents↗
PubMed1989

Decreased plasma membrane fluidity of peripheral blood lymphocytes after diethyldithiocarbamate (DTC) therapy in HIV-infected patients.

In seeking the putative mechanism of action of diethyldithiocarbamate (DTC) on the immune status of HIV infected patients, the plasma membrane fluidity of peripheral blood lymphocytes (PBL) from DTC-treated and untreated patients (CDC III-IVc1) was determined. Anisotropy values of the fluorescent probe 6-(9-anthroyloxy) stearic acid were increased in DTC-treated patients (0.175 vs 0.161), indicating decreased PBL plasma membrane fluidity. The membrane rigidifying effect was significantly greater 4 h after i.v. drug administration (0.185 in treated patients). As the membrane fluidity and the function of membrane embedded antigen are interdependent, it is possible that alterations in biophysical and/or biochemical properties of membranes may account for the beneficial effect of DTC on the immune function and clinical status of HIV infected patients.

Acquired Immunodeficiency Syndrome↗
PubMed1976

On the use of the spin labeling technique in the study of erythrocyte membranes.

ESR spectra and scanning electron micrographs of human erythrocytes spin labeled with the conventional stearic acid nitroxide substituted at the 5-position have been obtained over a range of label-to-lipid ratios. While morphological changes as previously reported (Bieri, V. G., Wallach, D. F. H. and Lin, P. S. (1974) Proc. Natl. Acad. Sci. U.S. 71, 4797-4801) are reproduced, it is shown that at label-to-lipid ratios of 1:10 or less the basic ESR spectrum is not significantly affected. At low label concentrations the spin labeling technique is a viable one and can be used to investigate membrane properties.

Binding Sites↗
PubMed1990

A spin label ESR and saturation transfer ESR study of alpha-tocopherol containing model membranes.

An investigation into the effect of alpha-tocopherol on phospholipid model membranes has been carried out by electron spin resonance (ESR) and saturation transfer ESR. The use of stearic acid and of perdeutero -di-t-butyl nitroxide spin probes has allowed us to monitor, in particular, the effect of alpha-tocopherol on both the phospholipid chain order and the phospholipid chain mobility. The results obtained are mainly consistent with a differing action of alpha-tocopherol in the gel and in the liquid crystalline phases: in the former it induces a decrease of order and an increase in fluidity; while in the latter phase an indication of a slight increase in ordering and a clear decrease in fluidity are registered.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1987

Studies of structural modifications induced by gamma-irradiation in distearoylphosphatidylcholine liposomes.

An investigation of the structural and thermodynamical modifications induced by gamma-irradiation in model membranes is reported. Differential scanning calorimetry and X-ray diffraction were used to study the different phases and associated transitions of distearoylphosphatidylcholine multilamellar liposomes after 60Co gamma-irradiation. Changes were observed in the shape of the calorimetric peaks and in the corresponding phase transition temperatures. In particular a shoulder was observed at about 20 kGy. The three phases characteristic of lecithins with identical acyl chains were detected also for the highest radiation dose. The formation of lysolecithin and stearic acid upon phospholipid degradation was observed. The lysolecithin concentration increases as a function of irradiation dose, until a saturation value is reached at 40 kGy. These results correlate quite well with those obtained for interlayer and interchain distances and for the width of the main phase transition calorimetric peak. At the highest dose (approximately equal to 80 kGy) cross-linked adjacent radicals and other molecular species are also formed. Appreciable differences, and some similarities, in the behaviour of DSPC and DPPC liposomes under gamma-irradiation were observed.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1976

An ESR study of the hydration steps of lecithin multilayers.

A spin-labeled stearic acid and other spin-labeled molecules have been used for an ESR study of the hydration process of the egg lecithin lamellar phase for water concentrations, CW greater than 10%. Two hydration steps are found for CW approximately 20% and CW congruent to 30%, in good agreement with results of the literature. To explain discontinuities in the behavior of three spin-labeled molecules at CW congruent to 20%, a conformational change of the phosphatidylcholine polar head and a phase transition in the polar interface are proposed.

Binding Sites↗
PubMed1989

The effect of added monoacylglycerols on the removal from plasma of chylomicron-like emulsions injected intravenously in rats.

Lipid emulsions were prepared with compositions similar to the triacylglycerol-rich plasma lipoproteins, but also incorporating added small amounts of monoacylglycerols. Control emulsions without monoacylglycerol were metabolized similarly to natural chylomicrons or very-low-density lipoproteins when injected intravenously in rats. The emulsion triacylglycerols and cholesteryl esters were both removed rapidly from the bloodstream, with the removal rates of triacylglycerols faster than those of cholesteryl esters. Much of the removed cholesteryl ester was found in the liver, but only a small fraction of the triacylglycerol, consistent with hepatic uptake of the triacylglycerol-depleted remnants of the injected emulsion. Emulsions incorporating added monooleoylglycerol or stearic acid were metabolized similarly. Added 1- or 2-monostearoylglycerol had no effect on triacylglycerol removal from plasma, but the removal rate of cholesteryl esters was decreased and less cholesteryl ester was found in the liver. These effects are similar to those recently described when emulsions and chylomicrons contained triacylglycerols with a saturated acyl chain at the glycerol 2-position, suggesting that saturated monoacylglycerol produced by the action of lipoprotein lipase may cause triacylglycerol-depleted remnant particles to remain in the plasma instead of being rapidly taken up by the liver.

Animals↗
PubMed1980

Fluidity changes in rat liver plasma membranes during regeneration.

The fluidity of the liver plasma membrane during the first cell cycle of hepatectomized rats has been investigated by means of stearic acid spin labels and of the fluorescence polarization of perylene. The order parameters of 5-doxylstearate, that probes the membrane surface, have been found lowered in the hepatectomized rats after 15 hours from operation, in comparison with anesthetised and sham-operated controls at the same time; on the contrary, the fluidity in the membrane core, as probed by 16-doxylstearate, is increased in all groups. The fluorescence polarization of perylene is also lower in the hepatectomized rats. The results suggest that liver regeneration is accompanied by a fluidity increase of the plasma membrane.

Animals↗
PubMed1976

Influence of hydrophobic materials on dissolution of a nondisintegrating hydrophilic solid (potassium chloride).

A nondisintegrating hydrophilic solid was covered with coatings of hydrophobic materials as a model to study their influence on dissolution rates. Both solution and sublimation techniques were satisfactory for producing coatings of stearic acid. Only a sublimation method was applicable to magnesium stearate, but the resulting coating consisted mainly of a pyrolysis product, stearone. Reductions in dissolution rates in a continuous-flow system could best be interpreted by assuming that they reflected changes in the area of the hydrophilic solid exposed to the solvent. This concept is based on the assumptions that the intrinsic dissolution rate of uncoated potassium chloride did not change and that no dissolution occurred from coated areas. The most important factors controlling the dissolution rate were the strength of attachment of the hydrophobic coat to the surface of the hydrophilic substrate and the thickness of the coat.

Ketones↗
PubMed1975

Investigation of some materials as dry binders for direct compression in tablet manufacture. Part 5: Effects of lubricants and flow conditions.

The effect of talc, magnesium stearate, stearic acid, and Acrawax C, which are commonly used as lubricants, on the dry-binding efficiency of tragacanth, polyethylene glycol 4000, polyvinylpyrrolidone, and mannitol were investigated. The effect of Aerosil which is sometimes utilized as a flow conditioner for directly compressible powder blends was also studied. The type and concentration of lubricant or flow conditioner appeared to influence the binding efficiency of the binders investigated to various degrees. The results showed that the bonding characteristics of all the binders tested except mannitol were reduced by the addition of the lubricants and the flow conditioner.

Chemistry, Pharmaceutical↗
PubMed2006

Effects of an amphipathic alpha-helical peptide on lateral pressure and water penetration in phosphatidylcholine and monoolein mixed membranes.

The physicochemical properties of mixed membranes of 1-palmitoyl-2-oleoylphosphatidylcholine (POPC) and a nonlamellar-forming lipid, 1-monoolein (MO), and the effects of an amphipathic alpha-helical peptide, 18A (DWLKAFYDKVAEKLKEAF), on the membranes were investigated by fluorescence measurements and 31P NMR. The intramolecular excimer formation of dipyrenylphosphatidylcholines showed that the increased lateral pressure near the bilayer center by MO is reduced by the lamellar-cubic phase transition at an MO mole fraction of 0.7, while the lateral pressure near the polar-apolar interface increases even through the phase transition. The fluorescence lifetime of 2-(9-anthroyloxy)stearic acid revealed that water penetration into the interface region increases with the MO fraction. The insertion of the 18A peptide into the membrane interface region decreased both the lateral pressure near the interface and water penetration, and shifted the lamellar-cubic phase transition to a higher MO fraction. This suggests that 18A induces a positive curvature strain and lowers the lateral pressure and water penetration. Furthermore, the increase in the MO fraction in POPC/MO LUV promoted partitioning of 18A to the membranes. This preferential binding to the MO-containing membranes is presumably ascribed to the propensity of 18A to reduce the membrane strain.

Fluorescence↗
PubMed1997

Rotational mobility of Ca2+-ATPase of sarcoplasmic reticulum in viscous media.

The rotational diffusion of Ca2(+)-ATPase [Ca2+,Mg2(+)-activated ATP phosphohydrolase E.C. 3.6.1.38] was studied in native sarcoplasmic reticulum membrane by saturation transfer ESR spectroscopy after covalent labelling of intramembranous sulfhydryl groups with nitroxyl derivative of maleimide (5-MSL) as a function of sucrose and glycerol in the suspending medium. The relative enzymatic activity of sarcoplasmic reticulum was followed by increasing the viscosity of the aqueous phase. The ATP hydrolysing activity of the enzyme decreased differently on adding sucrose and glycerol. In the case of sucrose the reciprocal of power dependence of viscosity was observed, whereas for glycerol an exponential decay law was obtained, indicating solvent-protein interaction. On increasing the viscosity of the aqueous phase by either sucrose or glycerol, no changes were observed in the intramembranous viscosity as measured using intercalated spin-labelled stearic acid (16-SASL). The effective rotational correlation time of the protein was measured, as a mobility parameter, using saturation transfer ESR spectroscopy and found to be increased linearly with the viscosity of the sucrose containing medium and for the extramembranous size a height of 6.8 nm was obtained, indicating that approx. 82% of the volume of Ca2(+)-ATPase protein is external to the sarcoplasmic reticulum. The addition of glycerol probably promoted protein-protein interaction, as indicated by the larger changes in rotational diffusion and non-linear viscosity dependence.

Animals↗