Binding Of Lecithin Research Articles

Evaluation of the effect of lecithin and nanolecithin in repairing membrane damage, maintaining membrane integrity, and improving human sperm function in the freezing-thawing process.

Our study aimed to evaluate the effects of lecithin nanoparticles on sperm quality during cryopreservation. In phase one, sperm-freezing media were prepared with lecithin concentrations (0.5%, 1%, and 2%) and lecithin nanoparticles of various sizes (50-100, 100-200, and ≥ 200nm). Post-thaw, sperm motility, viability, mitochondrial membrane potential (MMP), lipid peroxidation (measured by malondialdehyde, MDA), and DNA fragmentation were evaluated. In phase two, the acrosomal reaction was assessed in the best and worst-performing groups from phase one. DiI labeling detected interactions between lecithin nanoparticles and the sperm membrane. Field emission scanning electron microscopy (FESEM) examined the sperm membrane's surface structure and lecithin binding sites. Atomic force microscopy (AFM) assessed height differences in the sperm surface layer in the best-performing group from phase one. The group treated with 1% lecithin nanoparticles (50-100nm) showed significantly increased viability post-thaw compared to other groups, with reduced DNA fragmentation and MDA levels. While motility significantly decreased in all groups compared to before freezing levels, lower concentrations, and smaller particle sizes yielded better results. MMP also significantly decreased across all groups with no significant differences. The acrosomal reaction significantly decreased with 1% lecithin nanoparticles (50-100nm) compared to the 2% (≥ 200nm) group. DiI-labeled nanoparticles and FESEM revealed that lecithin nanoparticles primarily bound to and infiltrated the sperm membrane, particularly in the head and postacrosomal regions. Lecithin nanoparticles effectively bind to the sperm membrane, protecting it during the freeze-thaw process and improving sperm viability.

Lecithin Capping Ligands Enable Ultrastable Perovskite-Phase CsPbI3 Quantum Dots for Rec. 2020 Bright-Red Light-Emitting Diodes.

Bright-red light-emitting diodes (LEDs) with a narrow emission line width that emit between 620 and 635 nm are needed to meet the latest industry color standard for wide color gamut displays, Rec. 2020. CsPbI3 perovskite quantum dots (QDs) are one of the few known materials that are ideally suited to meet these criteria. Unfortunately, CsPbI3 perovskite QDs are prone to transform into a non-red-emitting phase and are subject to further degradation mechanisms when their luminescence wavelength is tuned to match that of the Rec. 2020 standard. Here, we show that zwitterionic lecithin ligands can stabilize the perovskite phase of CsPbI3 QDs for long periods in air for at least 6 months compared to a few days for control samples. LEDs fabricated with our ultrastable lecithin-capped CsPbI3 QDs exhibit an external quantum efficiency (EQE) of 7.1% for electroluminescence centered at 634 nm─a record for all-inorganic perovskite nanocrystals in Rec. 2020 red. Our devices achieve a maximum luminance of 1391 cd/m2 at 7.5 V, and their operational half-life is 33 min (T50) at 200 cd/m2─a 10-fold enhancement compared to control samples. Density functional theory results suggest that the surface strain in CsPbI3 QDs capped with the conventional ligands, oleic acid and oleylamine, contributes to the instability of the perovskite structural phase. On the other hand, lecithin binding induces virtually no surface strain and shows a stronger binding tendency for the CsPbI3 surface. Our study highlights the tremendous potential of zwitterionic ligands in stabilizing the perovskite phase and particle size of CsPbI3 QDs for various optoelectronic applications.

Phospholipids dock SARS-CoV-2 spike protein via hydrophobic interactions: a minimal in-silico study of lecithin nasal spray therapy.

Understanding the physical and chemical properties of viral infections at molecular scales is a major challenge for the scientific community more so with the outbreak of global pandemics. There is currently a lot of effort being placed in identifying molecules that could act as putative drugs or blockers of viral molecules. In this work, we computationally explore the importance in antiviral activity of a less studied class of molecules, namely surfactants. We employ all-atoms molecular dynamics simulations to study the interaction between the receptor-binding domain of the SARS-CoV-2 spike protein and the phospholipid lecithin (POPC), in water. Our microsecond simulations show a preferential binding of lecithin to the receptor-binding motif of SARS-CoV-2 with binding free energies significantly larger than k_mathrm{B}T. Furthermore, hydrophobic interactions involving lecithin non-polar tails dominate these binding events, which are also accompanied by dewetting of the receptor binding motif. Through an analysis of fluctuations in the radius of gyration of the receptor-binding domain, its contact maps with lecithin molecules, and distributions of water molecules near the binding region, we elucidate molecular interactions that may play an important role in interactions involving surfactant-type molecules and viruses. We discuss our minimal computational model in the context of lecithin-based liposomal nasal sprays as putative mitigating therapies for COVID-19.Supplementary InformationThe online version supplementary material available at 10.1140/epje/s10189-021-00137-3.

Responses to Higher Concentration Lecithin of Apoptosis Relevant Factors and Detection of Specific Lecithin Binding Proteins by AC-MS assay

Lecithin in mixed micelles attenuates cytotoxicity by interacting with proteins or other cell inclusions. The reaction was then captured via magnetic beads binding approach. This research proposal was designed to discover the impacts of lecithin on apoptosis relevant factors (including caspase 3/8/9 and PARP) by Western Blot and specific protein binding mechanism of lecithin detoxification pathway, using caco-2 cell model. Preliminary investigation of the properties of the proteins was conducted by MS (Mass Spectrometry) couplet to AC (Affinity Chromatography) assay. Further research of particular proteins was to identify the size and peptide sequence. This study also provided solid evidence for the previous research result, which was lecithin reduce cytotoxicity induced by SDC contained mixed micelles.

Endoplasmic Reticulum (ER) Stress Enhances Tip60 (A Histone Acetyltransferase) Binding to the Concanavalin A

Herein, we report that the concanavalin A binding of Tip60 (a target of the human immunodeficiency virus type 1-encoded transactivator Tat interacting protein 60 KD; a histone acetyltransferase; HAT) is enhanced as the result of endoplasmic reticulum (ER) stress. The cell expression of Tip60 combined with site-directed mutagenesis analysis was used to identify the glutamine 324 residue as the lecithin binding (Concanavalin A; Con A) site. The Tip60 N324A mutant strain, which seems to be the Con A binding-deficient, was attenuated the protein-protein interactions with FE65 and its protein stability, but its ability of G0-G1 cell cycle arrest was not interrupted. Interestingly, both HAT activity and the nuclear localization of Tip60 N324A mutant were enhanced than those of Tip60 WT. Thus, our results indicate that the Con A binding deficient of Tip60 seems to be one of the most pivotal posttranslational modifications (such as N-glycosylation) for its functional regulation signal, which is generated in response to ER stress.

A binding study of phospholipase A2 with lecithin, lysolecithin and their tetrahedral intermediates using molecular modeling.

We used molecular modeling to examine the binding of 1,2-dioctanoyl-sn-glycero-3-phosphocholine (a lecithin), 1-octanoyl-sn-glycero-3-phosphocholine (a lysolecithin) and their tetrahedral intermediates in the catalytic site of phospholipase A2 (PLA2). We performed energy minimization on each complex, computed the binding energy, determined the relative binding energy among the complexes and calculated the difference in inter- and intramolecular energies of the components in the complexes. We found that the calculated orientation of the sn-1 ester bond of lysolecithin in the active site is similar to that of the sn-2 ester bond in lecithin, thus permitting PLA2 to hydrolyze lysolecithin using the same mechanism as it uses to hydrolyze lecithin. On the other hand, the binding of lecithin is energetically more favorable by 4.5 kcal/mol than the binding of lysolecithin to the enzyme, and the binding of the lecithin tetrahedral intermediate is also energetically more favorable by 19.7 kcal/mol than the binding of the lysolecithin tetrahedral intermediate to the enzyme, which explains why lecithin is a better substrate than lysolecithin in the catalytic site. These results indicate that the activation energy for the hydrolysis of lysolecithin is higher than that for lecithin, consistent with the observed slower rate for the hydrolysis of lysolecithin.

Influence of vesicle surface composition on the interfacial binding of lecithin:cholesterol acyltransferase and apolipoprotein A-I

Interfacial binding affinities and capacities of lecithin:cholesterol acyltransferase (LCAT) and apolipoprotein A-I (apoA-I) for surfaces of different phosphatidylcholine (PC) composition, cholesterol content, and apolipoprotein content were measured with a vesicle model system. Native polyacrylamide gel electrophoresis was used to separate free protein from vesicle-bound protein. ApoA-I was isolated from human plasma and radiolabeled with iodine, whereas radiolabeled LCAT was purified from the media of Chinese hamster ovary cells that were transfected with human LCAT cDNA and incubated in the presence of [35S] cysteine and methionine. Bound and free radiolabeled LCAT and apoA-I were quantified by phosphorimage analysis. ApoA-I binding was not influenced by cholesterol content (14 mole%) but was influenced by the PC fatty acyl composition of the vesicle. PC species containing long chain, polyunsaturated fatty acids (PUFA) in the sn-2 position resulted in increased binding affinity (Kd = 75-177 nM) but reduced capacity (0.1-0.3 apoA-I/ 1000 PC) in comparison to sn-1 palmitoyl, sn-2 oleoyl PC (POPC, 750 nM and 1.4 apoA-I/1000 PC). LCAT binding affinity to POPC (2190 nM) was stronger in the presence of cholesterol (530 nM), and LCAT binding capacity was reduced (2.63 and 0.6 molecules LCAT/1000 PC, respectively). In comparison to POPC, LCAT binding affinity to sn-1 palmitoyl, sn-2 arachidonyl PC was stronger (611 nM) and binding capacity was reduced (0.7 LCAT/1000 PC). LCAT binding affinity and capacity to sn-1 palmitoyl, sn-2 eicosapentaneoyl PC (2041 nM, and 2.5 LCAT/1000 PC) were similar to those observed for POPC. We conclude that vesicle surface PC fatty acyl composition and cholesterol content significantly influence LCAT and apoA-I interfacial binding and therefore may alter LCAT enzymatic activity.

The diafiltration method for the study of the binding of macromolecules to heavy metals

A membrane process known as continuous diafiltration has been utilized as an effective method for the study of the binding of macromolecules to ions. Data from one experiment will result in an entire isotherm when temperature and pH are closely controlled. This paper discusses the theory of continuous diafiltration and describes a procedure for quantifying variable membrane rejection behavior. The binding of five heavy metals (Cd, Cu, Ni, Pb, Zn) individually and collectively, to natural lecithin was studied. Copper exhibited stronger binding when it was the lone ion compared to when it was in a mixture of the five metals. Further, the membrane rejected copper at a constant rate of 10% in the first case compared to a variable rate with an average of 79% in the second. This work was performed to characterization the binding of lecithin to heavy metals as a step in the development of a treatment technique termed micellar enhanced ultrafiltration.

Binding of lecithin:cholesterol acyltransferase to reconstituted high density lipoproteins is affected by their lipid but not apolipoprotein composition.

The reaction of lecithin:cholesterol acyltransferase (LCAT) with high density lipoproteins (HDL) is of critical importance in reverse cholesterol transport. We studied the relationship between LCAT binding and HDL composition using two assays to determine LCAT binding affinity for discoidal reconstituted HDL (rHDL). We prepared rHDL with egg phosphatidylcholine (egg-PC), cholesterol, and either apolipoprotein (apo) A-I or apoA-II. The rHDL, identical in lipid content, had sizes of 96 and 100 A, respectively. Binding constants (Kd) determined by the activity-inhibition method were 2.2 +/- 0.3 x 10(-7) and 1.1 +/- 0.3 x 10(-16) M, whereas those determined by a solid-phase method were 3.3 +/- 0.9 x 10(-7) and 3.7 +/- 0.9 x 10(-7) M for apoA-I and apoA-II rHDL, respectively. The stoichiometry was 1 LCAT bound/rHDL. The appVmax/appKm for apoA-I was 80-fold higher than for apoA-II rHDL. The large difference between LCAT-binding constants and enzymatic activity measurements for the two particles suggests that LCAT binding and activation by apolipoproteins are independent events. To determine the effects of phospholipid headgroup on LCAT binding affinity, we tested rHDL containing up to 16 mol % of egg phosphatidylethanolamine (egg-PE), egg phosphatidic acid (egg-PA), or bovine phosphatidylserine (PS). Kd was unchanged for PS rHDL, but increased 6-fold with increasing PE content. AppVmax increased with PE content, but decreased with PS or PA relative to egg-PC controls. AppKm increased in PE rHDL, but remained unchanged in rHDL with PA or PS. Fluorescence characterization of the lipid domains of rHDL shows small differences in the polarity of the headgroup region of PE rHDL. Thus, LCAT binding is influenced by the lipid, but not the protein composition of rHDL. AppVmax values reflect active site preferences, while appKm values reflect interfacial binding affinity.

Cooperativity in lipid activation of 3-hydroxybutyrate dehydrogenase: role of lecithin as an essential allosteric activator.

3-Hydroxybutyrate dehydrogenase (BDH) is a lecithin-requiring mitochondrial enzyme which catalyzes the interconversion of 3-hydroxybutyrate and acetoacetate with NAD(H) as coenzyme. The purified enzyme devoid of lipid (i.e., the apodehydrogenase or apoBDH) can be reactivated with soluble lecithin or by insertion into phospholipid vesicles containing lecithin. Two different models have been proposed to explain the sigmoidal lipid activation curves. For both models, activation of BDH is assumed to require the binding of two lecithin molecules per functional unit. Activation of soluble enzyme (dimeric form) by short-chain (soluble) lecithin is consistent with a model in which lecithin binding is noncooperative, whereas activation of the membrane-bound enzyme (tetrameric form) indicates cooperativity between the lecithin binding sites. A new comprehensive model is presented in which lecithin is considered to be an essential allosteric activator that shifts the equilibrium between conformational states of the enzyme. Resonance energy transfer data, reflecting NADH binding to membrane-bound and soluble apoBDH, are consistent with such a lecithin-induced conformational change. Apparent dissociation constants for binding of NADH to BDH are approximately 10 microM and approximately 37 microM for BDH activated by bilayer and soluble lecithin, respectively. The maximal fluorescence resonance energy transfer (delta F max) increases with higher mole fraction of lecithin in the bilayer. The largest changes occur between mole fractions 0 and 0.13, thereby correlating with enzymic function. Essentially no binding of NADH is observed in the absence of lecithin.(ABSTRACT TRUNCATED AT 250 WORDS)

Noncooperative vs. cooperative reactivation of D-beta-hydroxybutyrate dehydrogenase: multiple equilibria for lecithin binding are determined by the physical state (soluble vs. bilayer) and composition of the phospholipids.

D-beta-Hydroxybutyrate dehydrogenase (BDH) is a lecithin-requiring mitochondrial enzyme that catalyzes the interconversion of beta-hydroxybutyrate and acetoacetate. The purified soluble enzyme devoid of lipid (i.e., the apodehydrogenase) can be reactivated with soluble lecithin or by insertion into phospholipid vesicles containing lecithin. Lipid activation curves have a sigmoidal shape, and two models have been proposed to explain them. We have previously reported that the kinetics of reactivation with short-chain lecithins in the soluble state is consistent with a model in which the enzyme enzyme contains two identical, noninteracting lecithin binding sites, both of which must be occupied to activate the enzyme [noncooperative mechanism; Cortese, J.D., Vidal, J.C., Churchill, P., McIntyre, J.O., & Fleischer, S. (1982) Biochemistry 21, 3899-3908]. More recently a kinetic model involving cooperative interactions between lecithin binding sites was proposed for the reactivation of the membrane-bound enzyme [Sandermann, H., Jr., McIntyre, J.O., & Fleischer, S. (1986) J. Biol. Chem. 261, 6201-6208]. This study reinvestigates the basis for the different conclusions in these two studies. The previous study with soluble lecithins was limited to about 34% of maximal activation compared with mitochondrial phospholipid, due to inactivation of the enzyme at the critical micellar concentration. We could now extend this study to 91% activation by increasing the ethanol concentration. This experimental evidence confirms that the soluble system follows a noncooperative equation. We provide a new kinetic approach to test the cooperative model. A velocity equation is derived for a Hill-type cooperative ligand binding system interacting with a mixture of ligands. This equation predicts a proportionality between an overall weighted cooperative dissociation constant [Kcoop(w)] and a dissociation constant for a single lecithin (PC) species from interacting sites (KPC), regulated by the PC molar fraction (XPC): 1/Kcoop(w) = XPC/KPC. The equation was applied to the data of Sandermann et al. [Sandermann, H., Jr., McIntyre, J.O., & Fleischer, S. (1986) J. Biol. Chem. 261, 6201-6208] as well as to newly obtained data. The results obtained over a wide range of PC molar fractions and different mixtures of bilayer phospholipids fit this equation, confirming the cooperative behavior. We conclude that BDH has a different mode of reactivation depending on the nature of the lipid environment. With soluble lecithin, the activation is noncooperative, whereas in the bilayer, mixtures of phospholipids give cooperative behavior that fits a Hill equation.(ABSTRACT TRUNCATED AT 400 WORDS)

Site—site interaction in the lipid activation of β-hydroxybutyrate dehydrogenase

Kinetic data for the activation of the β-hydroxybutyrate dehydrogenase by long-chain lecithins [(1979) Biochemistry 18, 2420–2429; (1983) J. Biol. Chem. 258, 208–214] are analyzed. A previous kinetic model [(1982) Biochemistry 21, 3899–3908] is shown not to apply. Instead, the use of a two-site Adair equation points to a strongly cooperative interaction between the lecithin binding sites (Δ G, −2.8 kcal/mol).

Kinetic studies on the reactivation of d-β-hydroxybutyrate dehydrogenase with mixtures of short-chain lecithins

d-β-hydroxybutyrate dehydrogenase, purified as soluble, lipid-free apoenzyme (inactive) from rat liver mitochondria can be reactivated by the short-chain dihexanoyl, diheptanoyl, and dioctanoyl lecithins at the monomeric state, upon formation of a reversible enzyme-lecithin complex. Previous studies with these lecithins suggested that reactivation of the apoenzyme requires the simultaneous occupation of two identical, noninteracting lecithin binding sites via a rapid equilibrium random mechanism. The short-chain lecithins exhibited similar reactivating capacities, differing only in their affinities towards the enzyme. In order to further test that model, the reactivation of the apoenzyme was studied when two or three short-chain lecithins were simultaneously present in the reaction medium. The initial velocities were measured either as a function of the concentration of one lecithin while the other(s) were kept constant, or as a function of the total phospholipid concentration with mixtures of different lecithins at a constant molar ratio. The pertinent equations were derived on the principles of multiple equilibria with identical, noninteracting sites able to be occupied by any of the different lecithins present in the reaction medium, with the doubly occupied enzyme as the only active species. In agreement with the above-proposed model, the results obtained indicates that the molar fraction of the doubly occupied (active) enzyme species can be calculated from equilibrium considerations and that the maximal attainable with the different short-chain lecithins are similar.

Reactivation of D-beta-hydroxybutyrate dehydrogenase with short-chain lecithins: stoichiometry and kinetic mechanism.

D-beta-Hydroxybutyrate dehydrogenase (BDH), purified as soluble, lipid-free apoenzyme (inactive) from either beef heart or rat liver mitochondria, can be reactivated by short-chain lecithins in the monomeric state. The enzyme was reactivated with dihexanoyl- [PC(6:0)], diheptanoyl- [PC(7:0)], and dioctanoyllecithins [PC(8:0)]. The titration curves of enzyme activity as a function of the phospholipid concentration are consistent with a model in which the enzyme contains two identical, noninteracting lecithin binding sites. The simultaneous occupation of these sites (via an equilibrium random mechanism) is required to activate the apoenzyme. Similar results were obtained with both rat liver and beef heart apoenzymes. The maximal velocities obtained with the different lecithins were similar [110-140 mumol of NAD+ reduced min-1 (mg of protein)-1]. The KL values (the apparent dissociation constants of the lecithin-site complexes) were 1.2 X 10(-4) M [PC(8:0)], 1.5 X 10(-3) M [PC(7:0)], and 4.5 X 10(-3) M [PC(6:0)] at 37 degrees C. This was confirmed by using phospholipase A2 to compete with the dehydrogenase for the lecithin monomers. Comparison of the delta G degrees values for complex formation with the different lecithins shows an average contribution of approximately 2.4 kJ/mol (0.9RT) per CH2 group. The interaction of the apolar moiety of lecithin with the protein seems to be essential for effective binding of phosphatidylcholine to apoBDH. The delta G degrees values, when combined with the estimated delta H degrees values, suggest that the binding of lecithin to the apoenzyme is approximately 60% enthalpy and approximately 40% entropy driven.

Binding of cardiolipin/lecithin and monoamine oxidase to lipid-depleted mitochondrial membrane structure

Lipid-depleted pig liver mitochondrial residues were incubated with different proportions of the acidic phospholipid cardiolipin and the zwitterionic phospholipid lecithin in either separate or mixed liposomes. When cardiolipin and lecithin were present in separate liposomes all of the cardiolipin but no lecithin bound to the residues. When present in the same liposomes, cardiolipin also caused binding of lecithin to the mitochondrial residues. When monoamine oxidase solubilized from pig liver mitochondria by extraction of the phospholipids was included in the incubation, binding of the enzyme to the residues occurred in the presence of cardiolipin. The percentage of enzyme bound followed the same trend as the binding of phospholipids to the mitochondrial residues.

Sulfhydryl reagents and lecithin binding to butanol-extracted membranes

There is evidence suggesting that sulfhydryl groups play some role in protein structure. There is some evidence suggesting that protein sulfhydryl groups may be related in some way to lipid binding to certain proteins. The present studies were designed to show whether sulfhydryl reagent treatment of phospholipid-depleted lyophilized erythrocyte membranes would affect the subsequent binding of [ 14C]-lecithin to these membranes. The results indicate that inorganic and organic mercurials and iodoacetamide significantly depress the magnitude of labeled lecithin binding. Studies also show that this inhibition is proportionately greater for larger amounts of phospholipid bound than smaller.

Water lecithin binding in lecithin-water lamellar phases at 20°C

1H and 31P continuous wave and spin-echo NMR measurements have been made on lecithin-water mixtures as a function of water content at 20 °C. An analysis of the data demonstrates the existence of two water environments, lecithin bound and free. Conclusions are presented concerning the stoichiometry and kinetics of the binding. The results indicate that six molecules of water are bound to one lecithin molecule and the lifetime of the bound water is 6·10 −5±3·10 −5 s.

Erythrocyte Membrane Lipids and Rh Antigen Activity

The Rh antigens have never been totally and reproducibly obtained in free solution. Indirect evidence, based among other observations on the reversible loss of Rh antigen activity of lyophilized Rh-positive erythrocyte membranes with mercurial sulfhydryl reagents, suggests that the activity may depend on membrane protein. With the hypothesis that this membrane protein may be associated perhaps structurally with membrane lipid, studies were undertaken on the effects of organic solvents on lyophilized membrane Rh antigen activity. The antigen activity was abolished after extensive extraction with 100% 1-butanol, but could be regenerated to approximately 50% of the unextracted membranes by the addition of certain lipids. The present investigations establish that phospholipids are the only class of lipids which result in such regeneration. The binding of 14C-labeled lecithin of biological origin was measured in benzene solution, in sonicated aqueous dispersions, and in 5% methanol-ether dispersions. Regeneration of Rh activity was also followed, which showed that the binding of aqueous sonicated phospholipids (liposomes) was associated with the best regeneration and the maximum labeled lecithin bound. The binding of 14C-fatty acids also occurred under similar conditions, but no associated regeneration of Rh antigen activity was observed. Similarly, an extensive series of nonphosphorus-containing lipids failed to regenerate the antigen activity. Synthetic dipalmitoyl lecithin was found to bind to the 1-butanol-extracted membranes, but not to result in regenerated activity. Labeled phosphorylcholine showed little binding to these membranes, and large amounts of unlabeled phosphorylcholine only mildly depressed the binding of labeled lecithin. This suggests that the binding of the lecithin is predominantly hydrophobic. A graded effect of different phospholipids was noted in regard to the extent of antigen regeneration. Thus, the Rh antigen activity is dependent on the presence of bound phospholipid, containing at least one unsaturated fatty acid, with neither the polar nor the nonpolar portion of the molecule alone satisfying this requirement.

The influence of fatty acid composition on the rate of binding of lecithin by extracted mitochondria

1. (1)|A technique for measuring the rate of binding of lipid micelles by mitochondrial protein has been developed. 2. (2)|After an initial rapid uptake, lecithin micelles were bound by mitochondrial protein at a steady rate. With increasing concentrations of lecithin in micellar solutions this steady rate was increased towards a maximum rate. 3. (3)|These results have been interpreted as indicating that the binding was a two-step process, in which the second step was rate limiting. The first step was considered to be the collision of micelles with protein particles and the second a re-arrangement of micelles so that the lecithins formed bonds with structural protein. 4. (4)|Comparisons of the rates of binding of micelles of lecithins from normal and deficient rats has shown that fatty acid composition can influence this binding. Calculation from the experimental data showed that the maximum rate of binding of “deficient” lecithins was 2.5 to 3.0 times greater than that of “normal” lecithins. 5. (5)|These results suggest that the hydrophobic bonds between phospholipids and structural protein are influenced by fatty acid composition and that phospholipids from normal rats are bound by structural protein more slowly than are those from deficient rats. 6. (6)|It is suggested that structural protein has some special sites for hydrophobic bonding of arachidonic acid, in which phospholipids containing arachidonic acid are bound more slowly but also more firmly than other phospholipids. This could explain the reported fragility of lipoprotein membranes in animals deficient in essential fatty acids.

Comparative liberation of bound phosphatides from red cells of man, ox, and camel.

SummaryThe red cells of the camel are like those of true ruminants in being resistant to lysis by cobra venom but dissimilar in appearing to contain lecithin. The idea that the resistance of camel cells to venom is due to the binding of lecithin so that it is inaccessible to venom enzymes has been tested in terms of comparative extractability into ether-ethanol mixtures of phosphatides from cells of man, ox, and camel. The lipids were liberated much less readily in the case of the camel, indicating that the lipid complexes are different and more stable.