Dimyristoyl Lecithin Research Articles

Interaction of phospholipid vesicles with cells. Endocytosis and fusion as alternate mechanisms for the uptake of lipid-soluble and water-soluble molecules.

Depending on their phospholipid composition, liposomes are endocytosed by, or fuse with, the plasma membrane, of Acanthamoeba castellanii. Unilamellar egg lecithin vesicles are endocytosed by amoeba at 28 degrees C with equal uptake of the phospholipid bilayer and the contents of the internal aqueous space of the vesicles. Uptake is inhibited almost completely by incubation at 4 degrees C or in the presence of dinitrophenol. After uptake at 28 degrees C, the vesicle phospholipid can be visualized by electron microscope autoradiography within cytoplasmic vacuoles. In contrast, uptake of unilamellar dipalmitoyl lecithin vesicles and multilamellar dipalmitoyl lecithin liposomes is only partially inhibited at 4 degrees C, by dinitrophenol and by prior fixation of the amoebae with glutaraldehyde, each of which inhibits pinocytosis. Vesicle contents are taken up only about 40% as well as the phospholipid bilayer. Electron micrographs are compatible with the interpretation that dipalmitoyl lecithin vesicles fuse with the amoeba plasma membrane, adding their phospholipid to the cell surface, while their contents enter the cell cytoplasm. Dimyristoyl lecithin vesicles behave like egg lecithin vesicles while distearoyl lecithin vesicles behave like dipalmitoyl lecithin vesicles.

Apparent dependence of interactions between cytochrome b5 and cytochrome b5 reductase upon translational diffusion in dimyristoyl lecithin liposomes.

Dimyristoyl lecithin liposomes, containing cytochrome b5 reductase (NADH:ferricytochrome b5 oxidoreductase, EC 1.6.2.2) and varying amounts of cytochrome b5, were used to measure flavoprotein catalysis alone and catalysis requiring electron transfer between the reductase and cytochrome as a function of temperature. Whereas flavoprotein catalysis showed a simple linear temperature dependence in an Arrhenius plot, the reaction involving electron transfer between the two bound enzymes showed a marked, 4-fold, change in rate at the crystalline-liquid crystalline phase transition of the hydrocarbon chains of the lecithin vesicles and a second, minor change involving the minor transition. These data represent strong evidence that protein-protein interactions in this membrane model system are dependent upon translational diffusion of nonpolar segments of the proteins in the hydrocarbon region of the phospholipid bilayer.

Oxygen diffusion in biological and artificial membranes determined by the fluorochrome pyrene.

Quenching of pyrene fluorescence by oxygen was used to determine oxygen diffusion coefficients in phospholipid dispersions and erythrocyte plasma membranes. The fluorescence intensity and lifetime of pyrene in both artificial and natural membranes decreases about 80% in the presence of 1 atm O2, while the fluorescence excitation and emission spectra and the absorption spectrum are unaltered. Assuming the oxygen partition coefficient between membrane and aqueous phase to be 4.4, the diffusion coefficients for oxygen at 37 degrees C are 1.51 X 10(-5) cm2/s in dimyristoyl lecithin vesicles, 9.32 X 10(-6) cm2/s in dipalmitoyl lecithin vesicles, and 7.27 X 10(-6) cm2/s in erythrocyte plasma membranes. The heats of activation for oxygen diffusion are low (less than 3 kcal/degree-mol). A dramatic increase in the diffusion constant occurs at the phase transition of dimyristoyl and dipalmitoyl lecithin, which may result from an increase in either the oxygen diffusion coefficient, partition coefficient, or both. The significance of the change in oxygen diffusion below and above the phase transition for biological membranes is discussed.

Thermodynamic constants for nonelectrolyte partition between dimyristoyl lecithin and water.

Partition coefficients (K's) between dimyristoyl lecithin liposomes and water were measured as a function of temperature for 16 nonelectrolytes. FromK and its temperature dependence, the partial molar free energy (ΔF), enthalpy (ΔH) and entropy (ΔS) of partition for each solute were extracted. By subtraction of ΔF, ΔH and ΔS of hydration of each solute (where known), ΔF, ΔH and ΔS of solution in lecithin could be calculated for some solutes. Among different solutes ΔS of solution increases approximately linearly with ΔH of solution, as also found in bulk solvents (the so-called Barclay-Butler relations). The Barclay-Butler slopedΔS/dΔH is approximately twice as steep for lecithin as for bulk nonpolar solvents. This effect is attributed in part to greater immobilization of solutes in bilayers than in bulk solvents.

A method for measuring nonelectrolyte partition coefficients between liposomes and water.

This series of papers describes methods for measuring solute partition coefficients between membrane suspensions and water, and applies these methods to the system dimyristoyl lecithin: water. Knowledge of partition coefficients is relevant to analyzing permeability coefficients, probing membrane structure, and evaluating permeation models. The theoretical section of this first paper derives equations to correct measured partition coefficients for the effects of trapped water in the precipitate, tritium exchange with lipids or membranes and nonsolvent water adjacent to membranes. The experimental section presents methods for measuring partition coefficients in liposomes of dimyristoyl lecithin, including techniques for minimizing effects of counter drift and quenching on double-label radioactive counting. These methods offer advantages in measuring membrane: water partition coefficients that are not high.

Interpretation of nonelectrolyte partition coefficients between dimyristoyl lecithin and water.

Nonelectrolyte partition coefficients (K's) and free energies of solution (ΔF l 's) in dimyristoyl lecithin liposomes and in bulk nonpolar solvents were compared. Individual substituent groups tend to have consistent effects onK, permitting the extraction of incremental free energies (δΔF), enthalpies (δΔH), and entropies (δΔS) of partition and of solution. Values of the selectivity constants and of δΔF l for the −CH2−and −OH groups in lecithin suggest that partitioned solutes are mainly located in a region slightly less hydrophobic than octanol and similar to C5H11OH in its solvent properties. Lecithin discriminates against branched solutes more than does a bulk solvent with the sames value. Below the endothermic phase-transition temperature (i.e., when the hydrocarbon tails “freeze”), ΔS and ΔH of partition increase 10-fold,K jumps down slightly, ΔS and ΔH of solution reverse in sign from negative to positive, and the Barclay-Butler constants become more positive. Partition in lecithin and in erythrocytes is similar, except for the absence of surface charge effects in lecithin. Resistance to nonelectrolyte permeation is inhomogeneously distributed through the bilayer, and the region of maximum partition does not provide the rate-limiting barrier. An appendix derives a simple general expression for the nonelectrolyte permeability of a membrane that may be asymmetrical, may have position-dependent partition coefficients and diffusion coefficients, and may have significant interfacial resistances.

Nonsolvent water in liposomes.

In liposomes of dimyristoyl lecithin at 40°C, a quantity of water equal to about 11.5 moles water per mole lecithin, or about one-third of the enclosed liposome water or one-fifth of the total pellet water, behaves as if it is unavailable for dissolving sucrose. This phenomenon represents permanent exclusion of sucrose, not simply a space that equilibrates slowly due to the low permeability of sucrose. The amount of nonsolvent water increases with temperature, and is similar to the amount of water bound to the phosphorylcholine groups as estimated by other methods. Nonsolvent water arises from a combination of the forces responsible for “salting-out” of nonelectrolytes from aqueous solutions by ions, and of steric effects adjacent to a surface. Measured liposome: water partition coeffecients must be corrected for the effect of nonsolvent water.

Microcalorimetric study of phospholipid binding to human apo-HDL

The binding of lysolecithin and synthetic short-chain lecithins: di-caproyl, di-lauroyl and di-myristoyl lecithins to a human apo-high density lipoprotein (apo-HDL) was followed by microcalorimetry. Complex formation was checked by ultracentrifugal flotation. The binding reaction was very rapid and strongly exothermal. The apparent binding enthalpy ΔH B together with the complex composition were computed from the binding curves. Both quantities were of the same order of magnitude for lysolecithin and for the shorter chain lecithins while the binding of di-myristoyl lecithin was characterized by a more highly exothermal reaction. The structure of the lipid phase strongly influences the enthalpy change. In the case of lysolecithin and of the shorter chain lecithins; which form micellar structures in water, the enthalpy change is mainly due to apoprotein-phospholipid complex formation. The disrupture of the myelin figures formed by the di-myristoyl lecithin accounts for the complementary heat effect. The phospholipid composition of the complexes isolated by ultracentrifugal flotation was lower than that determined by microcalorimetry, due to the presence of high salt concentrations in the ultracentrifuge.

The interaction of apoprotein from porcine high-density lipoprotein with dimyristoyl phosphatidylcholine.

1 The interactions between the lipid and protein in complexes of dimyristoyl lecithin and porcine apoprotein were studied using electron spin resonance and fluorescent probes, dissolved in the lipid and covalently bonded to the protein. 2 The chain-melting transition of dimyristoyl lecithin is broadened on complexing with porcine apoprotein, indicating that the cooperative interaction between the lipid hydrocarbon chains is modified in the complex. 3 The broadening of the chain-melting transition is seen to be greatest by probes located at or near the glycerol region of the phospholipid. 4 Labels covalently bound to the protein experience only a small perturbation from the lipid chain-melting transition. 5 The results are interpreted as being consistent with a model for the complex, consisting of a lipid-bilayer, partially coated with protein and with some interdigitation of the protein.

Effect of exogenous lysolecithin of liposomal membranes its relation to membrane fluidity

The effect of exogenous lysolecithin on liposomal membranes has been studied. Lysolecithin did not have any significant influence on the glucose permeability of egg lecithin liposomes at any temperature range tested, unless the incubation temperature was shifted down from 21 °C to 1 °C. With the shift-down of the temperature, lysolecithin-induced damage of liposomes occurred. When liposomes were prepared with dimyristoyl lecithin, they were sensitive to lysolecithin in the temperature range from 40 °C to 21 °C without the necessity for a shift-down of temperature. Sensitivity of dimyristoyl lecithin liposomes to lysolecithin was shown to be completely dependent on the temperature. Below 10 °C, the damage of the liposomes by lysolecithin was negligible. With liposomes containing the equimolar mixture of dimyristoyl lecithin and egg lecithin, lysolecithin had the largest effect on the permeability of glucose at around 15 °C. Generally, cholesterol incorporation suppressed the sensitivity of liposomes to lysolecithin. The results obtained in this study indicate that lysolecithin-induced liposomal damage requires certain states of fluidity in lipid bilayers. It seems likely that the first interaction of liposome with lysolecithin and the following expression of permeability change may require different states of fluidity of lipid bilayer.

Lateral Mobility of Pyrene in Model Membranes of Phospholipids with Different Chain Length

AbstractThe coefficients of lateral diffusion, Dp, of pyrene in lipid bilayers of several 1,2‐diacyl‐phosphatidyl cholines (distearyllecithin (DSL), di‐palmitoyllecithin (DPL), dimyristoyllecithin (DML) and dilauryllecithin (DLL) above the corresponding lipid phase transition were determined. Dp was obtained from the second order rate constant, ka, of the pyrene excimer formation. It is found that the lateral mobility of an apolar molecule (such as pyrene) in the hydrophobic region of lipid lamella does not depend on the hydrocarbon chain length (Dp ≈︁ 2 · 10−7 cm2/sec at 60°C). The pyren mobility is characterized by an activation energy of ΔEp+ ≈︁ 10 kcal/mol. The experimental data are interpreted in terms of a simple model that is based on the assumption that the hopping frequency of a diffusing particle is determined by the rate of formation of free volume in the hydrocarbon moiety of the membrane. The latter is created by thermal activation of rotational isomers (essentially gtg‐kinks) in the hydrocarbon chains. The hopping frequency of the pyrene molecule is related to the jump frequency of the kinks along the hydrocarbon chains.

Binding of alkaline and alkaline earth cations in lecithin mesophases

The binding of ions in aqueous dimyristoyl lecithin mesophases was determined from the concentrations of electrolyte in the mesophase and in the purely aqueous electrolyte solution phase that coexists in equilibrium with the mesophase when large amounts of solution are present. Electrolytes studied included LiCl, NaCl, KCl, MgC1 2, CaC1 2, and BaCl 2. No evidence of binding was found with NaCl and KCl. Association “constants” computed for the binding of the other cations varied irregularly with the aqueous electrolyte solution phase concentration. The computed “constants” were about 0.4 for Li + and 1, 2 and 0.6, respectively, for Mg 2+, Ca 2+ and Ba 2+ ions, for a complex consisting of 1 phosphocholine group per cation, and 0.5, 1 and 0.4 for a complex consisting of 2 phosphocholine groups per cation.

The influence of the alkyl chain length of lecithins and lysolecithins on their interaction with α sl-casein

1. 1. The interactions between casein fractions and synthetic lecithins were examined by density gradient centrifugation as a function of the lipid alkyl chain length. Dicapryl (C 10) and dilauroyl (C 12) lecithin both formed lipid-protein complexes with α s1-casein but not with β-casein; also dicapryl lecithin did not interact with k-casein. Dimyristoyl (C 14) lecithin, however, showed no interaction with α s1-casein. 2. 2. The interactions between synthetic lysolecithins (C 10-C 20) and α s1-casein were also studied by density gradient ultracentrifugation. The results showed that the short-chain lysolecithins (C 10, C 12) formed complexes which had a tendency to dissociate under the experimental conditions used. C 14, C 16, and C 18 lysolecithins formed stable lipid-protein complexes whilst C 20 lysolecithin formed complexes with some difficulty. 3. 3. The experimental data have been correlated with the hydrophobic free energies of transfer of lipid monomer from water to lipid micelle (or bilayer).

An uncommon phosphatidylcholine specific for surface-active material in canine lung.

ArticleAn uncommon phosphatidylcholine specific for surface-active material in canine lung.R J King, J Ruch, and J A ClementsR J KingSearch for more papers by this author, J RuchSearch for more papers by this author, and J A ClementsSearch for more papers by this authorPublished Online:01 Nov 1973https://doi.org/10.1152/jappl.1973.35.5.778MoreSectionsPDF (1009 KB)Download PDF ToolsExport citationAdd to favoritesGet permissionsTrack citations ShareShare onFacebookTwitterLinkedInWeChat Previous Back to Top Next Download PDF FiguresReferencesRelatedInformation Cited ByDihydrotestosterone inhibits fibroblast-pneumonocyte factor-mediated synthesis of saturated phosphatidylcholine by fetal rat lung cellsBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol. 835, No. 1The phospholipids of lamellar body material from fetal rabbit lung tissue in culture. Unusual phosphatidylcholine fatty acid profileBiochimica et Biophysica Acta (BBA) - Lipids and Lipid Metabolism, Vol. 833, No. 1Lung surfactant phospholipids in different animal speciesLipids, Vol. 19, No. 11Membrane Composition, Structure, and FunctionMajor Phospholipids in SurfactantQuantitative determination of natural dipalmitoyl lecithin with dimyristoyl lecithin as internal standard by capillary gas-liquid chromatographyJournal of Chromatography A, Vol. 192, No. 1Pulmonary surfactant: Distribution of lipids, proteins and surface activity in ultracentrifugation of rabbit pulmonary washing and derived fractionsLipids, Vol. 12, No. 11LungRole of lamellar inclusions in surfactant production: studies on phospholipid composition and biosynthesis in rat and rabbit lung subcellular fractions.Journal of Lipid Research, Vol. 16, No. 6Phosphatidylglycerol in rat lung. II. Comparison of occurrence, composition, and metabolism in surfactant and residual lung fractions1 May 2002 | Biochemistry, Vol. 14, No. 4 More from this issue > Volume 35Issue 5November 1973Pages 778-81 https://doi.org/10.1152/jappl.1973.35.5.778PubMed4801133History Published online 1 November 1973 Published in print 1 November 1973 Metrics

Calorimetric Studies of Dilute Aqueous Suspensions of Bilayers Formed from Synthetic l-α-Lecithins

Abstract The gel-liquid crystal transitions in lipid bilayers formed from synthetic dimyristoyl, dipalmitoyl and distearoyl l-α-lecithins have been studied by high sensitivity differential scanning calorimetry in dilute aqueous suspensions ranging in concentration from 0.4 to 6.6 mg ml-1. Each lipid shows two endothermic transitions, an extremely sharp main transition and a broader transition accompanied by a smaller heat absorption at a temperature 5–10° below the main transition. The enthalpy increases in the main transition are respectively 6.3, 9.7, and 10.8 kcal per mole of monomeric lipid. The main transition widths, which are not very reproducible, reach a minimum in the case of dimyristoyl lecithin of as little as 0.2° for 10% to 90% conversion, suggesting that these transitions would be truly isothermal with completely pure lipids. The apparent heat capacities of the lipids in the liquid crystal state are, with the possible exception of dipalmitoyl lecithin, no more than 5 cal deg-1 (mole of lipid)-1 larger than in the gel state, indicating that the hydrocarbon chains have much less mobility in the liquid crystalline state than in the corresponding liquid normal paraffins. This conclusion was also reached by Phillips et al. (Phillips, M. C., Williams, R. M., and Chapman, D. (1969) Chem Phys. Lipids 3, 234) on the basis of entropy comparisons.

Lipid mobility in Acholeplasma membranes using deuteron magnetic resonance

Acholeplasma laidlawii B have been grown on media supplemented with perdeuterated lauric and palmitic acids. The lauric acid was shown to be elongated to myristic acid-d 23 and palmitic acid-d 23, and these acids were incorporated into the membrane lipids. Infrared measurements indicated the membrane proteins were predominantly α-helical. Deuteron magnetic resonance spectroscopy of the deuterated lipids in intact membranes indicated that the lipids were in a state of mobility rather similar to that of the gel state of dimyristoyl lecithin. This is consistent with our interpretation of results obtained by differential scanning calorimetry and X-ray diffraction. The existence of rigid lipid regions in organisms lacking cholesterol may not be uncommon, and may occur in E. coli also.

The interaction energies of cholesterol and lecithin in spread mixed monolayers at the air-water interface

1. 1. The interaction between dilauroyl lecithin, diundecyloyl lecithin, didecanoyl lecithin and dinonanoyl lecithin with cholesterol was investigated using the Goodrich method. No interaction with cholesterol was found for dinonanoyl lecithin, while with didecanoyl lecithin small effects could be detected only at high surface pressure. Strong condensation effects occurred with diundecyloyl lecithin and dilauroyl lecithin. The pressure-area curves of these lecithins are given. 2. 2. Assuming a regular surface mixture, a theory was derived which allows one to describe the collapse pressure of a mixed monolayer with miscible components. 3. 3. The interaction between distearoyl lecithin, dipalmitoyl lecithin, dimyristoyl lecithin, dilauroyl lecithin, diundecyloyl lecithin, didecanoyl lecithin, dinonanoyl lecithin, oleoyl-stearoyl lecithin, dioleoyl lecithin and dilinoleoyl lecithin with cholesterol was investigated by measuring the collapse pressure of the mixed monolayers. An interaction parameter and interaction energies were calculated. 4. 4. According to this method distearoyl lecithin, dipalmitoyl lecithin, dinonanoyl lecithin and dilinoleoyl lecithin showed no interaction with cholesterol; while dimyristoyl lecithin, dilauroyl lecithin, diundecyloyl lecithin, oleoyl-stearoyl lecithin and dioleoyl lecithin interacted markedly with cholesterol. A small effect was observed for didecanoyl lecithin. The most pronounced effect was observed for dilauroyl lecithin and oleoyl-stearoyl lecithin. 5. 5. The results obtained using the Goodrich and collapse pressure methods are in good agreement.

Longitudinal capillary waves. Part 2.—Experiments

It has been shown theoretically that longitudinal waves can easily be studied at an interface with a high elastic modulus. Measurements on mixed monolayers of cholesterol and dimyristoyl lecithin show that the behaviour of longitudinal waves is in accordance with predictions from theory. The elastic modulus at this interface as obtained from the wavelength of longitudinal waves at 200 c/sec, is several times the “equilibrium” modulus obtained from the slope of force-area curves.

Rates of replacement of lecithins and alveolar instability in rat lungs.

Rates of replacement of lecithins and alveolar instability in rat lungs.