Lecithin Molecules Research Articles

Characterization of a third phase transition in multilamellar dipalmitoyllecithin liposomes.

The thermotropism of dipalmitoyllecithin in fully hydrated multilamellar dispersions has been reexamined by differential scanning calorimetry, X-ray diffraction, and 31P nuclear magnetic resonance. Apart from the well-known pretransition and main transition, there exists a third transition at about 11 degrees C with a transition enthalpy of approximately 3.7 kcal/mol. Both adjoining phases are lamellar, but they differ in the lateral acyl chain packing of the lecithin molecules and in the dynamics of the polar head groups. The kinetics of this third phase transition are extremely slow in comparison with those of the other two transitions.

Brugia pahangi: Growth improvement with lecithin in the diet of axenically reared hosts, Aedes aegypti

Growth and development of the filarial nematode Brugia pahangi was examined in Aedes aegypti mosquitoes axenically reared on defined synthetic dietary media containing crude animal lecithin and synthetic dipalmitoyl lecithin. The first was a crude preparation containing impurities (mostly lipids) up to 40%, while the second was a highly purified preparation of lecithin (99.95%). Substantial proportions of apparently alive but undeveloped prefirst-stage parasite juveniles (presausage forms) were found in mosquitoes reared on all synthetic dietary media but not in mosquitoes reared on liver powder (control). Of the two lecithin preparations tested, parasites grew best in mosquitoes reared on a diet augmented with crude animal lecithin. Development was synchronized and the filarial parasites were able to complete two molts to become third-stage juveniles. Synthetic dl-dipalmitoyl lecithin in mosquito diets did not improve filarial development. The improvement of worm growth in terms of rate of morphogenesis and facility in molting, with the addition of crude, and not the pure lecithin preparation, suggested that the effect observed on filariae may not be directly due to the lecithin molecule, but due to a compound (probably a lipid), associated with the lecithin molecule in the crude preparation.

Novel surface phase containing cholesteryl esters. 1. Structural characteristics determined from surface pressure--area measurements.

The behavior of cholesteryl myristoleate in mixtures with dioleoylphosphatidylcholine was investigated at the air--water interface. In addition to the previously described monolayer phase [Smaby, J. M., Baumann, W. J., & Brockman, H. L. (1979) J. Lipid Res. 20, 789--795], a second surface phase has been identified. Analysis of surface pressure and molecular area data as a function of composition shows that the molecules in the second phase can exist in two miscible, double-layer states or packing arrangements, only one of which contains lecithin. The mixed double-layer state is preferentially formed and has stoichiometry ranging between 2.0 and 9.5 molecules of cholesteryl ester for each lecithin molecule. The structure of this state resembles a mixed monolayer of pressure-dependent composition and area which is covered by a second layer of cholesteryl ester at 38.2 A2/molecule. The cholesteryl myristoleate/lecithin ratio of the layer in contact with the aqueous phase ranges from 0 to 2.8 between 39 and 0 mN/m. The second double-layer state is equivalent to a monolayer of cholesteryl ester at the lipid--water interface, covered by a layer of cholesteryl ester molecules at 38.2 A2. Overall, our data show that the presence of lecithin at a lipid--water inferface has a definite ordering effect on cholesteryl ester molecules at least 30--50 A from the interface.

Magneto-orientation of lecithin crystals.

For the purpose of clarifying the magneto-orientation mechanism of several biological membrane systems, xylene-suspended thin-layered single crystals of lecithin, which is a major component of membranes, were subjected to magnetic fields of various strengths, and the orientation behavior of the crystals was analyzed. Lecithin crystals oriented in such a way that the directions of both the hydrocarbon chains and the phosphorylcholine group of the lecithin molecule were perpendicular to the magnetic field, suggesting that the crystals were diamagnetically biaxial. In contrast, hydrocarbon chains of phospholipids in many biological membranes are known to orient parallel to magnetic fields. The value of the volume diamagnetic susceptibility anisotropy, delta chi (i.e. the difference between susceptibilities parallel and perpendicular to the direction of the hydrocarbon chain in the lecithin crystals), estimated from the magneto-orientation behavior was about -9 X 10(-8) cgs. This is distinctly larger than that of vesicles of egg yolk lecithin measured by Boroske and Helfrich [Boroske, E. & Helfrich, W. (1978) Biophys. J. 24, 863-868] and also larger than that of single crystals of polyethylene, which was measured for comparison by the same technique as that used for lecithin in this study. The differences between these values of delta chi seem to result from the contribution of the polar head (i.e., the part of the lecithin molecule other than the two hydrocarbon chains), which is ordered, less ordered, or deleted in the respective cases above, although mainly from the contribution of the hydrocarbon chains, which are ordered in crystals and disordered in vesicles.

Liposomal Membranes. V. Interaction of Zinc(II) Ion with Egg Phosphatidylcholine Liposomes

Abstract The efficiency of encapsulation of several divalent metal ions, mainly Zn(II) ion, into egg lecithin liposomes has been investigated with particular attention to the stability of liposomal membranes against the transition metal(II) ions. The stronger interaction of metal ions to lecithins led to the less formation of liposomes. The addition of a suitable amount of nonionic detergent, 2-[ω-hydroxypentadeca(oxyethylene)-α-yl]-1,3-bis(dodecyloxy)propane (2C1215G, see text), enhanced the encapsulation of Zn(II) and Cu(II) ions in liposomes. The stoichiometric measurement for the binding of Zn(II) ion to single compartment liposomes of egg lecithin suggested that a Zn(II) ion is interacting with three or four lecithin molecules on the average in both halves of liposomal bilayers. Even under the circumstances, the bilayer structure of liposomes was certainly kept stable, which was electron micrographically visualized.

The lateral diffusion coefficient of lecithin molecules in single bilayer vesicles studied by 14N NMR

The 14N nuclear relaxation times T 1 and T 2 in egg yolk phosphatidylcholine have been observed in single bilayer vesicles dispersed in the media of different viscosities, 1H 2O and 2H 2O. The lateral diffusion coefficient of lipid molecule D has been calculated according to the method reported earlier: D = 2.2 × 10 −8cm 2s −1 in 1H 2O and 2.1 × 10 −8cm 2s −1 in 2H 2O at 20°C. They are in excellent agreement. This result gives a strong basis of usefulness of 14N NMR method in the evaluation of D without introducing any system perturbation.

Application of highly purified anti-galactocerebroside antibody to the analysis of lipid-lipid or lipid-protein interactions. Significance of lipid matrix.

The significance of the lipid matrix in the reaction of liposomal antigen, antibody and complement (Ag-Ab-C) was analyzed using purified anti-glactocerebroside antibody and synthetic lipids and the following results were obtained. 1. For the optimal Ag-Ab-C reaction it was necesary that galactocerebroside (galxCMH) and lecithin molecules were well dispersed by virtue of cholesterol (Chol) and that the molar ratio of cholesterol to the sum of galactocerebroside and lecithin was more than one. 2. The Ag-Ab-C reactivity changed depending upon the chain length of lecithin, and the maximal reaction was observed in the case of dilauroylphosphatidylcholine. When the fatty acyl chain of lecithin was either shorter or longer than that of dilaurosylphosphatidylcholine, the reactivity was reduced. 3. The Ag-Ab-C reactivity was increased by elongation of the fatty acyl chain of galactocerebroside and an abrupt change was found to be around the carbon number 8 to 10 of the fatty acyl chain. 4. The Ag-Ab-C reactivity was elevated by the increase in unsaturation of fatty acyl moiety. 5. There is a tendency that an increase in the charge of the lipid matrix leads to the reduction of the Ag-Ab-C reactivity. 6. The results suggest that the physicochemical properties of lipids and especially the lipid-lipid interaction in the hydrophobic region of the lipid matrix play an important role in the Ag-Ab-C reaction.

Does a chemically symmetric bond pattern induce a symmetric conformation of lecithin molecules in membranes?

Does a chemically symmetric bond pattern induce a symmetric conformation of lecithin molecules in membranes?

The structure of lipid bilayers and the effects of general anaesthetics: An X-ray and neutron diffraction study

We have looked for the effects of three clinically used inhalational anaesthetics (nitrous oxide, halothane and cyclopropane) on the structure of lecithin/ cholesterol bilayers. The anaesthetics were delivered to the membranes in the gaseous phase, so that effects at clinical concentrations could be determined. High-resolution X-ray diffraction patterns were recorded out to 4 Å and analyzed using swelling experiments. Parallel neutron diffraction experiments were performed and analyzed using H 2O- 2H 2O exchange. Methods were developed which enabled us to obtain confidence limits for the X-ray and neutron structure factors. The resultant X-ray and neutron scattering density profiles clearly define the positions of the principal molecular groups in the unperturbed bilayer. In particular, the high-resolution electron density profiles reveal features directly attributable to the cholesterol molecule. A comparison with the neutron scattering density profiles shows that cholesterol is anchored with its hydroxyl group at the water/hydrocarbon interface, aligned with the fatty acid ester groups of the lecithin molecule. We suggest that this positioning of the cholesterol molecule allows it to act as a thickness buffer for plasma membranes. In the presence of very high concentrations of general anaesthetics, the bilayers show increased disorder while maintaining constant membrane thickness. At surgical concentrations, however, there are no significant changes in bilayer structure at 95% confidence levels. We briefly review the literature previously used to support lipid bilayer hypotheses of general anaesthesia. We conclude that the lipid bilayer per se is not the primary site of action of general anaesthetics.

β-Carotene or chlorophyll a incorporated in lecithin liposomes. Analysis by ultracentrifugation

Ultracentrifugal analyses show that β-carotene and chlorophyll a are incorporated into the membranes of lecithin liposomes without any increase of the particle size. The sedimentation coefficient and particle weight of the liposomes increase up to a maximum value (4.3 S and 3.1 × 10 6 respectively) for a molar ratio of pigment to lecithin of about 0.02, due to an increasing number of lecithin molecules per particle. The pigments lower the average surface area of the polar heads of lecithin down to a minimum of 79 A 2/molecule. When the molar ratio of chlorophyll a to lecithin is above 0.02, the characteristics of the vesicles do not change, indicating a different type of incorporation of the chlorophyll molecules in the membranes.

PROPERTIES OF CHLOROPH'YLL‐LECITHIN VESICLES: ULTRACENTRIFUGATION, ABSORBANCE, EMISSION AND PHOTOBLEACHING

Abstract— Egg lecithin vesicles (liposomes) containing up to one Chl a per 11 lecithin molecules were prepared without sonication. Their absorbance and emission properties indicate that Chl is dispersed in the lecithin, that the vesicles are dispersed in the medium and that there is a strong quenching of fluorescence.Their photobleaching and chemical bleaching show that there is a negligible amount of colloidal Chl present. In vesicles with a Chl:lecithin molar ratio higher than 0.05, there are probably some small aggregates of Chl a in the bilayer.The ultracentrifugation of such vesicles shows that their sedimentation constant increases, though not regularly, with their relative Chl content

Magnetic anisotropy of egg lecithin membranes

Magnetic realignment and rotational diffusion of cylindrical egg lecithin vesicles were measured under a phase contrast microscope. The anisotropy of magnetic susceptibility times membrane thickness was calculated from the data for several thin-walled vesicles. The resulting values were assigned to discrete numbers of bilayers. The difference between the susceptibilities parallel and perpendicular to the long axes of the lecithin molecules is deduced to be X parallel - X perpendicular = -(0.28 +/- 0.02) . 10(-8) cgs at 23 degrees C, if a bilayer thickness of 60 A is assumed.

Change of Lecithin Aggregation Due to Valinomycin‐Lipid Interaction

AbstractValinomycin added to a suspension of lecithin vesicles with chlorophyll a or b incorporated into their membranes induces slight changes in the absorption spectrum of chlorophyll. The analysis of these changes revealed that this effect is not associated with the ionophoric properties of valinomycin but indicates a valinomycinlecithin interaction. As a consequence, the aggregational state of the lecithin molecules is altered in a domain which comprises about 40 lipids around one valinomycin molecule. The ability of the chlorophylls to detect different lipid aggregations arises from their solvatochromic behaviour. Using spectroscopic data for chlorophyll in different solvents, it could be inferred that a change in electrostatic interaction is the main reason for the difference of the spectrum of chlorophyll embedded in lecithin of different aggregational states. This interaction originates from a strong electric field associated with the polar moieties of the lipids which is much larger than the field imposed by transmembrane potentials. Hence the absorbance changes of chlorophyll due to such potentials are rather small compared to those induced by valinomycin.

Nuclear magnetic resonance and light scattering studies of the aggregation of dipalmitoyl-phosphatidylcholine-Benzene systems

Magnetic resonance, light scattering measurements and visual observations have been performed on lecithin-benzene systems as a function of temperature from 80 to −60°C and concentration from n = n benzene /n DPPC = 3−200 . From these measurements the transition curves from micellar solution to the crystalline state were deduced. More than 5 benzene molecules per lecithin molecule are necessary to get a micellar solution. Both the size of crystallites and the distribution of pores in the crystalline state depend on the rate of cooling and history. For the crystal structure a biporous model is suggested. At about 0°C the bulk of the benzene freezes, but a small amount of about 3 benzene molecules per lecithin molecule remains unfrozen to about −50°C. The systems studied show considerable temperature hysteresis and ageing effects. Small amounts of water of one to two water molecules per lecithin molecule drastically change the properties of the lecithin systems.

Effect of viscosity on the width of the methylene proton magnetic resonance line in sonicated phospholipid bilayer vesicles

Several experimenters [ l-41 have reported that the methylene proton magnetic resonance (PMR) linewidth in small single bilayer vesicles is constant for a wide range of viscosities. They have consequentially inferred that the only molecular motions responsible for narrowing of the methylene line in vesicles are rapid conformational isomerizations and other motions of the hydrocarbon chains rather than the diffusion of phospholipid molecules around the vesicles or vesicular Brownian tumbling, which should be a function of the viscosity of the suspending medium. Because the methylene PMR line is two orders of magnitude broader in large multilamellar phospholipid dispersions than in small vesicles, it was deduced that the degree of disorder resulting from acyl chain isomerizations is substantially greater in vesicles than in multilamellar dispersions. However, in a recent phosphorus magnetic resonance investigation [5], the phosphorus line from the headgroups of dipalmitoyl lecithin and egg yolk lecithin (EYL) in small vesicles was shown to exhibit a dependence on the medium viscosity which was entirely consistent with the phosphorus line being narrowed by vesicular Brownian tumbling and by phospholipid diffusion. Furthermore, values of the diffusion constant D for the phospholipid molecules calculated from the data were in good agreement with independent measurements of the diffusion constant in sonicated and unsonicated phospholipid dispersions by other methods [4,6&9]. In contradiction to published results we present in this communication clear experimental evidence that the PMR methylene linewidth in small vesicles is dependent on the viscosity of the suspending medium and we extract a diffusion constant for egg yolk lecithin molecules in bilayers in agreement with that obtained by other techniques. We shall conclude that the difference in widths between the methylene line in vesicles and in multilamellar dispersions is determined by Brownian tumbling and lateral diffusion and that there is no need to invoke large additional narrowing mechanisms.

Equilibrium Penetration of Monolayers IV: Dipalmitoyllecithin–Cetrimonium Bromide System

Equilibrium surface pressure-area isotherms of dipalmi-toyllecithin monolayers were measured on substrates containing various concentrations of the surfactant, cetrimonium (hexadecyltrimethylam-monium) bromide. From these isotherms, the saturation adsorptions of surfactant for various surface lecithin concentrations were calculated. Plotting of these adsorptions against the inverse of the area per lecithin molecule, as required for the “accessible area” theory, revealed two linear segments, corresponding to penetration at high and at low monolayer areas. At both high and low areas, the adsorption into the accessible areas of the surface was similar to adsorption at a monolayer-free surface. The effective cross-sectional area of the monolayer molecule in the low area region was equal to the collapse area; in the high area region, it was equal to an area corresponding to the co-area, as calculated from the Amagat equation. The change in cross-sectional area corresponded to the transition in the monolayer from a liquid condensed state to a liquid expanded state.

Intermolecular interaction in the egg lecithin monolayers spread on aqueous alcohol solutions (author's transl)

The egg lecithin (PC) monolayer was spread on an aqueous butanol or hexanol solution, and the surface pressure-molecular area curves were obtained. From the increase of surface pressure by penetration of alcohol molecules into lecithin monolayer, the amount, penetrated or adsorbed amount, was calculated from the following equation [numerical formula] and the adsorption isotherms of Langmuir type were obtained. The amount of saturated adsorption of alcohol and k, the parameter which represents the affinity of adsorption, were calculated from the linear relation between C/T and C (alcohol concentration). The saturated amount of alcohol decreased with increase in surface concentration of lecithin, but k became minimum. This was explained by the cavity model. The lecithin monolayer penetrated by alcohol molecules forms a mixed monolayer of lecithin and alcohol. The mean area of mixed monolayer was larger than the area calculated by assuming additivity of the area of each component. It was concluded that alcohol molecules penetrating into the lecithin monolayer decrease the cohesive force between lecithin molecules.

人胃癌燐脂質に関する生化学的研究特に lecithin の脂肪酸分子内分布について

Lecithins are important constituents of biomembranes. In general, saturated fatty acids are present predominantly in the α-position and unsaturated ones in the β-position of lecithins. However, this positional specificity (of the fatty acids) is not always found, particularly in some experimental tumor lipids. It is described in this paper that lecithi ns of human stomach cancers were subjected to elucidate the positional specificity of the constituent fatty acids and the results obtained were as follows.1. There was no significant difference in phospholipid composition between normal and cancer stomach tissues.2. The main constituent fatty acids of the lecithins isolated from both stomach tissues were,16:0,16:1,18: 0,18:1,18:2 and 20: 4.3. In lecithins of cancer tissues, compared to normal ones,16:0 decreased and 18:0,18: 1,18: 2 and 20: 4 increased, resulting in more unsaturates were present in th e lecithin molecules than the saturates. At the α-position, the decrease of 16:0 and increase of 18: 0,18: 1 and 18: 2 were found and the decrease of 16:0 was over the increase of 18:0. At the,β-position,18:1 and 16:0 decreased and 18: 2 a nd 20:4 increased.The finding suggested that some metabolic disorders of lecithins were present in stomach cancer tissue.

Deuteron nuclear magnetic resonance studies of phase equilibria in a lecithin-water system.

Water deuteron NMR spectra have been studied for the system dipalmitoyllecithin (DPL)-heavy water (D2O) at different compositions and temperatures. From an analysis of the spectra in terms of quadrupole splittings, a phase diagram has been constructed for the temperature range 25-60 degrees C and the composition range 4-15 mol of D2O/mol of DPL. Evidence is given that the "pretransition" observed by differential scanning calorimetry is caused by a crossing of a three-phase line. Strong support for a specific hydration of about 11 water molecules per lecithin molecule in the phase between the pretransition and main transition is also found.

Pigment containing lipid vesicles

It was shown previously (Walz, 1976) that chlorophylla incorporated into the membrane of lecithin vesicles is a probe which detects the aggregational state of the lipids. This phenomenon is interpreted in terms of a solvatochromism, i.e., the effect of various solvents on the absorption spectrum of the solute. The sensor characteristics can be expressed by a set of solvatochromic coefficients, which are pertinent to the electronic transitions occuring in chlorophylla on excitation with light, and by means of the absorption bands associated with these transitions. An unambiguous resolution of spectra into absorption bands is not yet practicable, but at least part of the bands can be approximated by, Gaussian components which then allows us to estimate the solvatochromic coefficients From these data and based on the currently available theoretical and experimental information about, solvatochromism, it is concluded that the chromophore, i.e., the porphyrin ring of chlorophylla, is located adjacent to the glycerol-ester moieties of the lecithin molecules in the membrane, and that the sensor ability relies on different orientations of the chromophore for lecithin in different states of aggregation.