Phase behaviour of stearic acid-stearonitrile mixtures. A thermodynamic study in bulk and at the air-water interface

The solid-liquid phase behaviour of stearic acid (SA) and stearonitrile (SN) in binary mixtures was investigated by differential scanning calorimetry (DSC), and the formation of SA-SN mixed monolayers at the air-water interface was followed by surface pressure-area (pi-A) measurements and by Brewster angle microscope (BAM) observation. The solid-liquid phase diagram is a eutectic type phase diagram, with the eutectic composition 0.90相似文献   

Properties of cholesteryl esters in pure and mixed monolayers

The surface properties of cholesteryl palmitate, stearate, linoleate, linolenate, arachidonate, and acetate were investigated. Long-chain esters were not surface-active and force-area (pi-A) isotherms were not obtained. Unsaturated cholesteryl esters were oxidized at the air-water interface and these oxidized lipids gave expanded pi-A isotherms. Cholesteryl acetate had an equilibrium spreading pressure of 14.0 dynes/cm and formed a stable monolayer indistinguishable from cholesterol below that surface pressure. Cholesteryl linoleate formed mixed monolayers with surface-active lipids, and the amount of cholesteryl linoleate in the monolayer depended both on its solubility in the other lipid and on the surface pressure. Even at moderate surface pressures cholesteryl linoleate was extruded from the monolayer into a bulk phase. Cholesteryl acetate exhibited the well-known condensing effect of cholesterol in mixed monolayers with egg lecithin.     

Miscibility critical pressures in monolayers of ternary lipid mixtures

When phospholipids are mixed with cholesterol in a monolayer at an air-water interface, coexisting 2-dimensional liquid phases can be observed if the surface pressure, pi, is lower than the miscibility critical pressure, pi(c). Ternary mixtures of two phospholipid species with dihydrocholesterol have been reported to have critical pressures that are linearly proportional to the relative composition of the phospholipids. However, we report here that, if the acyl chains of the two phospholipids differ significantly in length or unsaturation, the behavior is markedly different. In this case, the critical pressure of the ternary mixture can be remarkably high, exceeding the critical pressures of the corresponding binary mixtures. High critical pressures are also seen in binary mixtures of phospholipid and dihydrocholesterol when the two acyl chains of the phospholipid differ sufficiently in length. Using regular solution theory, we interpret the elevated critical pressures of these mixtures as an attractive interaction between the phospholipid components.     

Molecular packing of high-density and low-density lipoprotein surface lipids and apolipoprotein A-I binding

The surface pressure (pi)-molecular area (A) isotherms for monolayers of human high-density lipoprotein (HDL3) and low-density lipoprotein (LDL) phospholipids and of mixed monolayers of these phospholipids with cholesterol spread at the air-water interface were used to deduce the likely molecular packing at the surfaces of HDL3 and LDL particles. LDL phospholipids form more condensed monolayers than HDL3 phospholipids; for example, the molecular areas of LDL and HDL3 phospholipids at pi = 10 dyn/cm are 88 and 75 A2/molecule, respectively. The closer packing in the LDL phospholipids monolayer can be attributed to the higher contents of saturated phosphatidylcholines and sphingomyelin relative to HDL3. Cholesterol condenses both HDL3 and LDL phospholipid monolayers but has a greater condensing effect on the LDL phospholipid monolayer. The pi-A isotherms for mixed monolayer of HDL3 phospholipid/cholesterol and LDL phospholipid/cholesterol at stoichiometries similar to those at the surfaces of lipoprotein particles suggest that the monolayer at the surface of the LDL particle is significantly more condensed than that at the surface of the HDL3 particle. The closer lateral packing in LDL is due to at least three factors: (1) the difference in phospholipid composition; (2) the higher unesterified cholesterol content in LDL; and (3) a stronger interaction between cholesterol and LDL phospholipids relative to HDL3 phospholipids. The influence of lipid molecular packing on the affinity of human apolipoprotein A-I (apo A-I) for HDL3 and LDL surface lipids was evaluated by monitoring the adsorption of 14C-methylated apo A-I to monolayers of these lipids spread at various initial surface pressures (pi i).(ABSTRACT TRUNCATED AT 250 WORDS)     

Enzyme-catalyzed oxidation of cholesterol in mixed phospholipid monolayers reveals the stoichiometry at which free cholesterol clusters disappear.

In this study, we have used cholesterol oxidase as a probe to study cholesterol/phospholipid interactions in mixed monolayers at the air/water interface. Mixed monolayers, containing a single phospholipid class and cholesterol at differing cholesterol/phospholipid molar ratios, were exposed to cholesterol oxidase at a lateral surface pressure of 20 mN/m (at 22 degrees C). At equimolar ratios of cholesterol to phospholipid, the average rate of cholesterol oxidation was fastest in unsaturated phosphatidylcholine mixed monolayers (1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine and egg yolk phosphatidylcholine), intermediate in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine, and slowest in sphingomyelin monolayers (egg yolk or bovine brain sphingomyelin). The average oxidation rate in mixed monolayers was not exclusively a function of monolayer packing density, since egg yolk and bovine brain sphingomyelin mixed monolayers occupied similar mean molecular areas even though the measured average oxidation rate was different with these two phospholipids. This suggests that the phospholipid acyl chain composition influenced the oxidation rate. The importance of the phospholipid acyl chain length on influencing the average oxidation rate was further examined in defined phosphatidylcholine mixed monolayers. The average oxidation rate decreased linearly with increasing acyl chain lengths (from di-8:0 to di-18:0). When the average oxidation rate was examined as a function of the cholesterol to phospholipid (C/PL) molar ratio in the monolayer, the otherwise linear function displayed a clear break at a 1:1 stoichiometry with phosphatidylcholine mixed monolayers, and at a 2:1 C/PL stoichiometry with sphingomyelin mixed monolayers.(ABSTRACT TRUNCATED AT 250 WORDS)     

Stability of fatty acid monolayers and the relationship between equilibrium spreading pressure, phase transformations, and polymorphic crystal forms

Force-area isotherms were obtained for hexadecanoic, octadecanoic, eicosanoic, and docosanoic acid monolayers at different compression rates. Equilibrium spreading pressures were determined both by monolayer collapse and by spreading from the bulk phase. Monolayers formed metastable phases at all pressures above their equilibrium spreading pressures and at all surface areas smaller than the surface areas at their equilibrium spreading pressures. These metastable phases collapsed to stable phases at the equilibrium spreading pressures of the fatty acids. Collapse phenomena and compression experiments at very slow compression rates suggested that a previously unrecognized phase transformation occurred at the equilibrium spreading pressure. The surface area at this phase transformation corresponded to the cross-sectional area of the C-form of the fatty acid crystal. Fatty acid monolayers at the phase transformations previously described by other workers had surface areas which were closely related to molecular areas in their A and B polymorphic crystal forms. These correlations indicated that molecular structure in saturated fatty acid monolayers was similar to molecular structure in fatty acid crystals.     

Effects of a cationic and hydrophobic peptide, KL4, on model lung surfactant lipid monolayers.

We report on the surface behavior of a hydrophobic, cationic peptide, [lysine-(leucine)4]4-lysine (KL4), spread at the air/water interface at 25 degrees C and pH 7.2, and its effect at very low molar ratios on the surface properties of the zwitterionic phospholipid 1,2-dipalmitoylphosphatidylcholine (DPPC), and the anionic forms of 1-palmitoyl-2-oleoylphosphatidylglycerol (POPG) and palmitic acid (PA), in various combinations. Surface properties were evaluated by measuring equilibrium spreading pressures (pi(e)) and surface pressure-area isotherms (pi-A) with the Wilhelmy plate technique. Surface phase separation was observed with fluorescence microscopy. KL4 itself forms a single-phase monolayer, stable up to a surface pressure pi of 30 mN/m, and forms an immiscible monolayer mixture with DPPC. No strong interaction was detected between POPG and KL4 in the low pi region, whereas a stable monolayer of the PA/KL4 binary mixture forms, which is attributed to ionic interactions between oppositely charged PA and KL4. KL4 has significant effects on the DPPC/POPG mixture, in that it promotes surface phase separation while also increasing pi(e) and pi(max), and these effects are greatly enhanced in the presence of PA. In the model we have proposed, KL4 facilitates the separation of DPPC-rich and POPG/PA-rich phases to achieve surface refinement. It is these two phases that can fulfill the important lung surfactant functions of high surface pressure stability and efficient spreading.     

Phase behaviour of stearic acid-stearonitrile mixtures: A thermodynamic study in bulk and at the air-water interface

The solid-liquid phase behaviour of stearic acid (SA) and stearonitrile (SN) in binary mixtures was investigated by differential scanning calorimetry (DSC), and the formation of SA-SN mixed monolayers at the air-water interface was followed by surface pressure-area (π-A) measurements and by Brewster angle microscope (BAM) observation. The solid-liquid phase diagram is a eutectic type phase diagram, with the eutectic composition 0.90 < X_SN < 0.95 and T^eut = 40.9 °C. The DSC results also suggest that the two components are immiscible in the solid phase but form a liquid mixture with positive deviations to the ideal behaviour. At the air-water interface, the two components form liquid condensed monolayers in the entire range of compositions, at low surface pressures, while solid mixed monolayers only form at high surface pressures for X_SN < 0.8. Thermodynamic analysis indicates that SA and SN are miscible in the liquid condensed phase, with negative deviations from the ideal behaviour. The variation of the collapse surface pressure of mixed monolayers also indicates miscibility at the air-water interface.     

A comparative study of the phase transitions of phospholipid bilayers and monolayers

Phase transitions in bilayers and monolayers of various synthetic phospholipids with different chain lengths as well as different polar head groups were studied by differential scanning calorimetry or with the film balance technique, respectively. With the film balance, area versus temperature curves (isobars) were recorded at different surface pressures. The monolayer phase transition from the fluid-condensed to the fluid-expanded phase is shifted towards higher temperature when the lateral pressure in the monolayer is increased. The temperature dependence of the equilibrium pressure as well as the magnitude of the area change at the transition depends only on the nature of the phospholipid head group and not on the chain length of the hydrocarbon chains of the lipid. Phospholipids with strong intermolecular attractive interactions between the head groups show low values for dpi/dTm and for the area change, deltaf, whereas phospholipids with negatively charged head groups without intermolecular attractive forces exhibit higher values for dpi/dTm and deltaf. The shift of the monolayer phase transition temperature when increasing the chain length of the lipid is almost identical to the shift in Tm observed for the bilayer system of the same phospholipids. A comparison of monolayer and bilayer systems on the basis of the absolute value of the molecular area of the phospholipid in the bilayer gel phase and the change in area at the bilayer and monolayer transition leads to the following conclusions. The behaviour of the bilayer system is very similar to that of the respective monolayer system at a lateral pressure of approx. 30 dyne/cm, because at this pressure the absolute area and the area change in both systems are the same. Further support for this conclusion comes from the experimental finding that a lateral pressure of 30 dyne/cm the shift in Tm due to the increase in charge when the methyl ester of phosphatidic acid is investigated is the same for the bilayer and the monolayer system.     

Rapid compression transforms interfacial monolayers of pulmonary surfactant

Films of pulmonary surfactant in the lung are metastable at surface pressures well above the equilibrium spreading pressure of 45 mN/m but commonly collapse at that pressure when compressed in vitro. The studies reported here determined the effect of compression rate on the ability of monolayers containing extracted calf surfactant at 37 degrees C to maintain very high surface pressures on the continuous interface of a captive bubble. Increasing the rate from 2 A(2)/phospholipid/min (i.e., 3% of (initial area at 40 mN/m)/min) to 23%/s produced only transient increases to 48 mN/m. Above a threshold rate of 32%/s, however, surface pressures reached > 68 mN/m. After the rapid compression, static films maintained surface pressures within +/- 1 mN/m both at these maximum values and at lower pressures following expansion at < 5%/min to > or = 45 mN/m. Experiments with dimyristoyl phosphatidylcholine at 37 degrees C produced similar results. These findings indicate that compression at rates comparable to values in the lungs can transform at least some phospholipid monolayers from a form that collapses readily at the equilibrium spreading pressure to one that is metastable for prolonged periods at higher pressures. Our results also suggest that transformation of surfactant films can occur without refinement of their composition.     

Interaction of plasma apolipoproteins with lipid monolayers.

The monolayer technique has been used to study the interaction of lipids with plasma apolipoproteins. Apolipoprotein C-II and C-III from human very low density lipoproteins, apolipoprotein A-I from human high density lipoproteins and arginine-rich protein from swine very low density lipoproteins were studied. The injection of each apoprotein underneath a monolayer of egg phosphatidy[14C]choline at 20 mN/m caused an increase in surface pressure to approximately 30 mN/m. With apolipoprotein C-II and apolipoprotein C-III there was a decrease in surface radioactivity indicating that the apoproteins were removing phospholipid from the interface; the removal of phospholipid was specific for apolipoprotein C-II and apolipoprotein C-III. Although there was a removal of phospholipid from the monolayer, the surface pressure remained constant and was due to the accumulation of apoprotein at the interface. The rate of surface radioactivity decrease was a function of protein concentration, required lipid in a fluid state and, of the lipids tested, was specific for phosphatidylcholine. Cholesterol and phosphatidylinositol were not removed from the interface. The addition of 33 mol% cholesterol to the phosphatidylcholine monolayer did not affect the removal of phospholipids by apolipoprotein C-III. The addition of phospholipid liposomes to the subphase greatly facilitated the apolipoprotein C-II-mediated removal of phospholipid from the interface. Although apolipoprotein A-I and arginine-rich protein gave surface pressure increases, phospholipid was only slightly removed fromthe interface by the addition of liposomes. Based on these findings, we conclude that the apolipoproteins C interact specifically with phosphatidylcholine at the interface. This interaction is important as it relates to the transfer of the apolipoproteins C and phospholipids from very low density lipoproteins to other plasma lipoproteins. The addition of human plasma high density lipoproteins or very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of phosphatidyl[14C]choline from the interface 3--4 fold. Low density lipoproteins did not affect the rate of decrease. During lipolysis of very low density lipoproteins to the subphase increased the apolipoprotein C-mediated removal of with the lipid monolayer. Lipolysis experiments were performed in a monolayer trough containing a surface film of egg phosphatidyl[14C]choline and a subphase of very low density lipoproteins and bovine serum albumin. Lipolysis was initiated by the addition of purified milk lipoprotein lipase to the subphase. As a result of lipolysis, there was a decrease in surface radioactivity of phosphatidylcholine. The pre-addition of high density lipoproteins decreased the rate of decrease in surface radioactivity...     

Phospholipid monolayers at the triolein-saline interface: production of microemulsion particles and conversion of monolayers to bilayers

Interfacial tensions of phospholipid monolayer at the triolein (TO)-saline interface were measured. The adsorption isotherms and the interfacial pressure-molecular area curves were evaluated on the basis of the measurements. Phosphatidylcholine (PC) forms a highly condensed monolayer, with a large lateral attractive interaction; phosphatidylethanolamine (PE) and phosphatidylserine (PS) form expanded monolayers with smaller lateral interaction energies. At the lowest interfacial tension (the highest interfacial pressure), the mole fractions of PC, PE, and PS in the monolayers are estimated as 0.95, 0.73, and 0.88, respectively. Therefore, PC forms the most stable monolayer at the interface. These results are consistent with the finding that the stable TO particles in aqueous solution were produced by using PC as an emulsifier, and PE and PS did not stabilize the particles. The phase diagram of TO and PC mixtures in saline obtained from theoretical considerations predicts the equilibrium conversion of the monolayers on TO particles to bilayers. This process may be closely related to the transformations of very low density lipoproteins and chylomicrons to high-density lipoproteins in plasma. The particle sizes of the emulsion are calculated theoretically as a function of PC mole fraction in the TO-PC mixture and compared with the experimental values obtained from quasi-elastic light scattering (QLS) measurements.     

Peripheral protein adsorption to lipid-water interfaces: the free area theory

In fluid monolayers approaching collapse, phospholipids and their complexes with diacylglycerols hinder adsorption to the monolayer of the amphipathic protein, colipase. Herein, a statistical, free-area model, analogous to that used to analyze two-dimensional lipid diffusion, is developed to describe regulation by lipids of the initial rate of protein adsorption from the bulk aqueous phase to the lipid-water interface. It is successfully applied to rate data for colipase adsorption to phospholipid alone and yields realistic values of the two model parameters; the phospholipid excluded area and the critical free surface area required to initiate adsorption. The model is further developed and applied to analyze colipase adsorption rates to mixed monolayers of phospholipid and phospholipid-diacylglycerol complexes. The results are consistent with complexes being stably associated over the physiologically relevant range of lipid packing densities and being randomly distributed with uncomplexed phospholipid molecules. Thus, complexes should form in fluid regions of cellular membranes at sites of diacylglycerol generation. If so, by analogy with the behavior of colipase, increasing diacylglycerol may not trigger translocation of some amphipathic peripheral proteins until its abundance locally exceeds its mole fraction in complexes with membrane phospholipids.     

The relationship between cell injury and osmotic volume reduction: IV. The behavior of hardy wheat membrane lipids in monolayer

Lipid extracts from two winter wheat cultivars, Kharkov and Champlein, were studied as monomolecular layers on a Langmuir trough. An abrupt collapse of the lipid monolayers from unhardened and hardened Champlein and unhardened Kharkov was observed at pressures of 22 to 25 dynes/cm with only little return of lipid to the interface on removal of pressure. In marked contrast, the more hardy cultivar, Kharkov, in hardened state, contained lipids which progressively migrated from the interface on increasing pressure but returned with decreasing pressure, the collapse pressure being 16 to 19 dynes/cm². The same trends held true for purified phospholipids from both cultivars and treatments with the exception that the collapse pressure of hardened Kharkov phospholipid rose to the same 20 to 25 dynes/ cm range as the other purified extracts.In an attempt to duplicate conditions obtaining in a plasmolyzing cell, hardened Kharkov phospholipids were layered on a diluted aqueous cell extract, intensifying the hardening effects already observed with Kharkov total lipid extract on water and permitting a complete recovery of lipid on decompression of the monolayer. We conclude that an important element of freezing injury in winter wheat is the irreversible loss of membrane material, especially lipids, from cell membranes and that the unique reversibility of this process in hardened Kharkov greatly extends its freezing resistance.     

Thyroid Hormones Affect the Membrane Dipolar Organization. Is It a General Event in Their Non-genomic Action?

The surface balance technique was employed to study the interactions of 3,5,3',5' tetraiodo L-thyronine, 3,5,3' triiodo L-thyronine, and 3,5-diiodothyronine with monomolecular phospholipid monolayers spread at the air-water interface. With this technique the insertion of thyroid hormones into egg yolk phosphatidylcholine was investigated. An increase of surface pressure and a substantial decrement in surface potential were observed after the injection of these hormones beneath a phospholipid monolayer. The negative dipole contribution upon hormone interaction opposes the well-known positive contribution of phospholipids. These effects correlated with iodo content of the thyroid molecule analogues 3,5,3',5' tetraiodo L-thyronine >3,5,3' triiodo L-thyronine >3,5-diiodothyronine. To our knowledge, these observations suggest a new and surprising effect of thyroid hormones on the regulation of transmembrane dipolar organization.     

Vinculin-lipid monolayer interactions: a model for focal contact formation

Vinculin-lipid interactions were investigated in a modified Langmuir trough. Provided proper conditions, vinculin had the potential to penetrate into phospholipid monolayers and to form rigid, cohesive protein films even at phospholipid monolayer pressures similar to those assumed to exist in living cell membranes. The equilibrium constant for this reaction was estimated to be on the order of 2.5 X 10(-9) to 2.2 X 10(-7) mol/liter (for pressures between 25 and 35 mN/m). Penetration velocity depended on lipid composition: it was high with acidic phospholipids, intermediate with mixtures of acidic and neutral phospholipids, and low with neutral phospholipids. Electron microscopy of freeze-dried/metal-shadowed vinculin films, recovered from the phospholipid monolayer surface, revealed relatively tightly packed globular particles, 13 to 18 nm in diameter, on average significantly larger than the particles seen in glycerol-sprayed and rotary metal-shadowed preparations of soluble vinculin. The lipid monolayer penetration ability of vinculin appears to depend on its conformation. Acid treatment or low salt buffers induced reversible changes in vinculin conformation such that it abolished its lipid penetration potential. These conformational changes could be documented by both circular dichroism and fluorescence spectroscopy. These results indicate that in the focal contact area vinculin may act like a "glue" and link, in a reversible way, stress fibers of cultured cells via their anchor proteins to the extracellular matrix.     

Activation of protein kinase C in lipid monolayers

The potential of lipid monolayers spread at an air-water interface was investigated as a well defined membrane model able to support protein kinase C (PKC) association and activation. PKC association to a mixed phospholipid film (phosphatidylcholine, phosphatidylserine) could be detected by an increase of the monolayer surface pressure. This association was strikingly dependent upon the presence of submicromolar concentrations of Ca2+. The effect of Ca2+ resulted in an increase of the PKC penetration into the lipid core at a given permissive surface pressure as well as in a marked increase of the critical surface pressure (29-38 dynes/cm) above which the enzyme was excluded from the membrane. Inclusion of diacylglycerol or tetradecanoate phorbol acetate (TPA) did not modify the PKC-monolayer association in a detectable manner. PKC associated to the lipid layer exhibited the expected catalytic property and was fully activated when diacylglycerol or TPA was included in the membrane. PKC activity was highly dependent upon the surface pressure of the lipid monolayer, being optimal between 30 and 35 dynes/cm. Study of the compression isotherm of various diacylglycerol structures revealed that all potent PKC agonists exhibited an expanded liquid phase behavior with collapse pressure below 40 dynes/cm, in contrast to weak activators which showed condensed isotherms with high collapse pressure (approximately equal to 60 dynes/cm). These observations showed that the lipid monolayer system is well adapted to the study of the molecular mechanisms involved in the regulation of PKC activity at a model membrane interface. They are in line with the suggestion of a major role of Ca2+ in the association (translocation) of PKC to membrane in living cell and suggest that diacylglycerol (and TPA) might activate membrane-associated PKC through local change in the surrounding lipid phase organization.     

The influence of phytohormones on the properties of wheat phospholipid monolayers at the water-air interface

The surface behaviour of monolayers of wheat phospholipids in the presence of phytohormones introduced into the water phase was studied using Langmuir's method. The phospholipids were extracted from the plasmalemma of non-embryogenic (NE) and embryogenic (E) calli initiated from two types of explant: immature inflorescences (inf) and embryos (emb). The surface properties were investigated in model systems of monolayers of mixed phospholipids with: 1) natural amphiphile composition (PL); 2) a determined hydrophobic part (16:0) and the natural percentage composition of the hydrophilic part (PPL); and 3) a determined hydrophilic part (PC) and the natural percentage composition of the hydrophobic part (HPL). The lower limit values of the molecular area (A(lim)) were observed for NE rather than for E monolayers in all the investigated systems (PL, PPL and HPL). The collapse pressure (pi(coll)) of the monolayer decreased in the order PPL>PL>HPL, indicating the high stability of monolayers containing saturated hydrocarbon chains. The injection of non-surface-active phytohormones into the water subphase and the subsequent formation of natural and also artificial phospholipid monolayers of E and NE causes a decrease in monolayer stability against collapse and molecular close packing. As a result of their amphipathic (hydrophilic-hydrophobic) structure, the surface properties of E phospholipids are probably optimal for these systems. The decreasing stability of the NE monolayer caused by the presence of the phytohormone seems to be advantageous in terms of membrane preparation for the differentiation process. All the investigated lipid monolayers (highly) stimulated the adsorption of indole-3-acetic acid (to the highest extent/degree) (among the examined phytohormones) from the subphase. Zearalenone had a significant influence on the surface properties of NE PPL and NE HPL monolayers. This may be connected with the ability of this phytohormone to affect the non-embryogenic structure of wheat. An anomalous temperature effect was observed in the presence of indole-3-acetic acid (IAA) in the bulk; phospholipid monolayers of embryogenic calli induced from embryos (E emb) when the temperature decreased from 25 to 15 degrees C. This phenomenon is ascribed to the dehydration of the polar groups in the monolayer     

Thermotropic behavior of liposomes from egg yolk lecithin, hydrogenized egg yolk lecithin and their mixtures

The thermotropic properties of multilamellar liposomes from egg yolk lecithin, hydrogenized egg yolk lecithin and several mixtures of these two lipids were studied with the application of excimer--forming optical probe pyrene and microcalorimetry. It was discovered that when the proportion of the egg yolk lecithin in the lipid mixture was raised the temperature of the main phase transition reduced. For all this, independent of the lipid mixture composition when the temperature was raised, apparently, polarity of pyrene microenvironment in the liposomes bilayers decreased. On the basis of the analysis of solidus and liquidus curves obtained from calorimetric studies of the lipid mixtures and bend points of Arrhenius anamorphose obtained during the pyrene excimer formation measurements some conclusions were made about the role of unmodified and hydrogenized egg yolk lecithin cluster formation in the determination of thermotropic properties of the liposomes from the above two lipids mixtures. High temperature phase transition discovered for the egg yolk lecithin while measuring the pyrene excimer formation is proposed to be closely connected with temperature-dependent changes in the organization of phospholipid heads on the interphase bilayer/H2O solution.     

Interferon incorporated into liposomes. A method for the design of homologous and heterologous liposomes and the control of their in-vivo permeability]

The specific features of the fatty acid composition of phospholipid carriers obtained from raw materials of vegetable and animal origin were studied. Differences in the enrichment of phospholipids of different origin with polyene fatty acids were shown. The method for obtaining fluoroliposomes incorporating such components as phospholipids of mouse organs, egg yolk, etc. were proposed. The study proved that the homology of the lipid base of liposomes facilitated their binding by tropic organs and more rapid liberation of the blood stream from them. The selection of lipid carriers and their sources was determined by their uniformity, morpho-functional importance, phospholipid and fatty acid composition, as well as their homology as regards their composition features.