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PubMed1986

Vesicular stomatitis virus binds and fuses with phospholipid domain in target cell membranes.

Fusion of vesicular stomatitis virus with some cells (HELR 66, KB, and human erythrocytes, both intact and trypsinized) and liposomes made of various natural and synthetic lipids was studied with spin-labeled phospholipid. Binding of virus was assayed separately with radiolabeled and spin-labeled virus. Binding to cells and liposomes was small at neutral pH but enhanced at acidic pHs. Fusion with cells and liposomes was negligibly small at neutral pH but greatly activated at acidic pHs lower than 6.5. Activation of fusion occurred at lower pH values than enhancement of binding. Fusion occurred rapidly and efficiently, reaching a plateau at 50-80% after 3 min at 37 degrees C. Binding and fusion with cells were enhanced by pretreatment of cells with trypsin. Binding to liposomes was dependent on the head group of the phospholipid, stronger to phosphatidylserine than to phosphatidylcholine, but not much dependent on the acyl chain composition. On the other hand, cis-unsaturated acyl chains were required for the efficient fusion, but there was only a small, if any, requirement for the head group. Cholesterol enhanced the fusion further. High fusion efficiency with cis-unsaturated phospholipids cannot be ascribed to the membrane fluidity but may be related to higher tail-to-head volume ratios. Possible mode of interaction of viral G glycoprotein with phospholipid is discussed. The virus cell entry mechanism is suggested as binding to the phospholipid domain in the cell surface membranes, endocytosis, and followed by fusion with the phospholipid domain in endosomes upon acidification.

Cell Line↗
PubMed1986

Interaction of europium(III) with phospholipid vesicles as monitored by laser-excited europium(III) luminescence.

The technique of laser-excited Eu(III) luminescence was applied to monitor Eu(III) binding to a variety of phospholipids. Eu(III) excitation spectra were similar with and without the presence of neutral phospholipids, while acidic phospholipids changed the spectrum in a concentration-dependent manner. Eu(III) appears to bind to the phosphate moiety with at least a 2:1 phospholipid:metal ion stoichiometry. Analysis of luminescence lifetimes reveals that only one or two waters of hydration are removed from Eu(III) by addition of neutral phospholipids, whereas acidic phospholipids and inorganic phosphate strip off all but one or two waters. Implications with regard to fusion and use of lanthanides as probes in membrane preparations are discussed.

Europium↗
PubMed1987

Quantitative contributions of cholesterol and the individual classes of phospholipids and their degree of fatty acyl (un)saturation to membrane fluidity measured by fluorescence polarization.

Steady-state fluorescence polarization (P) measurements, using the probe 1,6-diphenyl-1,3,5-hexatriene, in a large variety of well-defined liposomes at 25 degrees C allowed a quantitative description of the contributions of cholesterol, sphingomyelin, and (un)saturation of fatty acyl groups in the various phospholipids to the structural order (or the mutual affinity) of membrane lipids. The P values for liposomes prepared from lipid extracts of natural (purified) membranes of various origins could be more or less predicted (calculated) from the relative contributions of the individual lipid components. In all cases, the polarization varied with the cholesterol/phospholipid molar ratio (C/PL) according to the equation P = Pplat -(Pplat -Pzero) exp(-alpha C/PL), in which Pzero refers to the polarization without cholesterol and Pplat is a maximal plateau value, reached at a high C/PL (greater than 1). The "cholesterol-ordering coefficient" alpha of the phospholipids was found to increase with the fraction of sphingomyelin or dipalmitoylphosphatidylcholine molecules, indicating that the susceptibility of phospholipids to be ordered by cholesterol is increased by these compounds. Pzero increases curvilinearly with the fraction of either of these molecules. Pplat increases linearly with the fraction of saturated acyl chains for most phospholipids. Highly unsaturated fatty acyl chains (e.g., 20:4 and 22:6) strongly depress Pplat but not Pzero. The results suggest that such phospholipids are unlikely to associate with cholesterol and may thus create extremely fluid membrane domains. The disproportionation of cholesterol in the cell can be understood by the differing composition of the phospholipids in plasma membranes and endomembranes and their ordering susceptibility (affinity) toward cholesterol.

Animals↗
PubMed1987

Novel fluorescent phospholipids for assays of lipid mixing between membranes.

A series of fluorescent phospholipids has been synthesized, by a general and versatile procedure, with various fluorescent groups attached to the methyl-terminal half of one acyl chain in an otherwise normal phospholipid structure. Phospholipids labeled with (dialkylamino)coumarin moieties, and to a slightly lesser extent those labeled with a bimane group, exhibit a strong and stable blue fluorescence in phospholipid dispersions that is relatively insensitive to the physical state of the lipid phase. The fluorescence of these labeled phospholipids is efficiently quenched by resonance energy transfer to lipids labeled with a [[(dimethylamino)phenyl]azo]phenyl or a methyl(nitrobenzoxadiazolyl)amino group when these acceptors are incorporated into the same bilayer as the donor species. Acyl chain labeled phospholipid probes, both of whose chains are at least sixteen carbons in length, exchange extremely slowly between lipid vesicles (less than 1% exchange/h). These properties allow various donor-acceptor combinations of probes to be employed in sensitive and reliable assays of lipid mixing accompanying membrane fusion. We demonstrate that, in two particularly demanding applications (assays of the calcium-mediated coalescence of phosphatidylserine vesicles and of the proton-triggered coalescence of phosphatidylethanolamine vesicles), some combinations of acyl chain labeled probes offer substantial advantages over the commonly used N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)phosphatidylethanolamine/N-(l issamine rhodamine B sulfonyl)phosphatidylethanolamine pair to monitor accurately the progress of lipid mixing between vesicles.

Fluorescent Dyes↗
PubMed1990

Protein-mediated phospholipid translocation in the endoplasmic reticulum with a low lipid specificity.

The outside-inside translocation rate of various amphiphilic spin-labeled phospholipids has been measured in rat liver endoplasmic reticulum vesicles. The eight spin-labels tested experienced a fast flip-flop rate with the same half-time of approximately 20 min at 37 degrees C. The stationary distribution of these phospholipid analogues was ca. 45% on the inner vesicular leaflet and 55% on the external one, showing that there is no net enrichment of some lipid in one layer under the experimental conditions used. The initial rate of translocation was reduced 4-fold if membranes were preincubated with N-ethylmaleimide (2 mM) and was about an order of magnitude lower in liposomes made from the extracted lipids. An apparent saturability of the transbilayer diffusion can be deduced from the variation of the initial velocity of the relocation kinetics vs the amount of analogue incorporated in the membrane. Moreover, translocation rates of two different spin-labeled phospholipids introduced simultaneously in the membrane were almost equally reduced by the presence of the other lipid. On the other hand, no competition between the water-soluble dibutyroylphosphatidylcholine and the amphiphilic spin-labeled phospholipids could be detected. Overall, these results suggest that phospholipid translocation in the endoplasmic reticulum is a protein-mediated process with a low specificity, which tends, in the absence of any other metabolic event, to equilibrate the phospholipid composition of the two membrane halves.

Animals↗
PubMed1978

Location and interactions of phospholipid and cholesterol in human low density lipoprotein from 31P nuclear magnetic resonance.

The major phospholipids, phosphatidylcholine and spingomyelin, of low density lipoprotein (LDL) are accessible to small amounts of Pr3+, suggesting that the head groups of all mobile phospholipids are on the surface of the particle in contact with the aqueous medium. The major source of the nuclear Overhauser effect enhancement of 31P resonances is the N-methyl proton of the choline moiety, indicating close N-methyl phosphate group interactions, probably similar to those found previously in phospholipid vesicles. This behavior of the phospholipid head groups in LDL is similar to that in small vesicles without cholesterol, suggesting that in LDL most of the cholesterol is not associated with mobile, surface phospholipids. In contrast to LDL, where the presence of a large protein immobilizes some phospholipid head groups, immobilization does not occur in high density lipoprotein, consistent with occurrence of smaller peptides in the latter.

Chemical Phenomena↗
PubMed1978

Effect of membrane phospholipid compositional changes on adenylate cyclase in LM cells.

Adenylate cyclase activities were examined in mouse LM cell membranes which had been supplemented with polar head groups and/or fatty acids. Basal, fluoride-, and PGE1-stimulated activities varied systematically with changes in phospholipid composition, and PGE1-stimulated activities correlated with the average degree of unsaturation of the phospholipid fatty acids or with the primary amino group character of the phospholipid polar head groups. In addition, the Km for ATP of basal adenylate cyclase was systematically changed by both polar head group and fatty acid supplementation. Alteration of the membrane lipid composition also changed the temperature dependence of the enzyme and the lag time between addition of PGE1 and the onset of a change in catalytic rate. However, none of the alterations in the enzyme activity could be correlated with the viscosities of supplemented membranes and, instead, seemed to be characteristic for a specific polar head group or fatty acid composition. The data suggest a specific interaction of the enzyme with phospholipids and indicate that structural features of phospholipids may play a role in regulating adenylate cyclase activity. It is proposed that adenylate cyclase can exist in several different conformations in the membrane depending upon the phospholipid composition.

Adenylyl Cyclases↗
PubMed2005

Phospholipid regulates the activation of factor X by tissue factor/factor VIIa (TF/VIIa) via substrate and product interactions.

Although the phospholipid requirement for tissue factor (TF) activity has been well-established, the mechanism by which the surface regulates enzymatic activity remains unclear. We added phospholipid vesicles to already relipidated TF (30/70 PS/PC) and found that added lipid can both enhance and inhibit the rate of factor X (F.X) activation. Using active-site-inhibited F.Xa we demonstrate that F.Xa is a more potent inhibitor of TF/VIIa at lower lipid concentrations, and that this inhibition is attributable to high surface occupancy by F.Xa near the enzyme. We also find that exactly twice as many F.Xa molecules are bound to a lipid surface at saturation as F.X, and that a dimer model of F.Xa binding to the lipid can account for the experimentally observed, preferential binding of F.Xa (compared to F.X) to phospholipid surfaces. We manipulated the amount of phospholipid available to each TF molecule by controlling vesicle size and the number of TF molecules per vesicle and found that, as the 2D radius of phospholipid available to each TF molecule was increased, the observed k(cat) increased hyperbolically toward a maximum or "true k(cat)". At a 2D lipid radius of approximately 37 nm, the observed k(cat) was 50% of the "true k(cat)". Thus, phospholipid surface serves as a conduit for F.X presentation and F.Xa removal, and the rate at which F.Xa leaves the vicinity of the enzyme, either by lateral diffusion or desorption from the surface, regulates the rate of F.X activation. We argue that these findings require reevaluation of existing models of coagulation.

Binding, Competitive↗
PubMed2006

Characterization of the interaction of single tryptophan containing mutants of IpaC from Shigella flexneri with phospholipid membranes.

Shigella flexneri causes dysentery after invading the epithelial cells of the human colon. Enterocyte invasion is induced by the bacterial effector IpaC (invasion plasmid antigen C), which triggers Shigella entry into epithelial cells by a rather poorly understood mechanism. IpaC is also involved in pathogen escape into the host cell cytoplasm following uptake, and this property may be reflected in its ability to disrupt phospholipid vesicles in vitro. Purified recombinant IpaC interacts with liposome vesicles to cause the release of small molecules trapped inside. This interaction requires that the liposomes possess an acidic phospholipid component. To better understand the events involved in the disruption of liposomes by IpaC, single tryptophan mutants were generated to permit the use of intrinsic fluorescence, circular dichroism, and ultraviolet absorption spectroscopies to examine the effect that phospholipid membrane association has on IpaC structure and stability. These mutants were also used to determine how amino acid substitutions within specific regions of IpaC influence its activity in vivo. The outcomes of this study include findings that cholesterol greatly impacts IpaC association with phospholipid membranes, tryptophan incorporation into specific regions of IpaC (especially near the C-terminus) can greatly impact its in vivo activity, and interaction with phospholipid membranes causes differing degrees of change in the fluorescence of tryptophan residues introduced at specific sites within IpaC. These data, together with fluorescence quenching analyses, provide new functional and structural information concerning IpaC and its insertion into phospholipid membranes.

Amino Acid Substitution↗
PubMed1996

Fatty acids and anionic phospholipids alter the palmitoyl coenzyme A kinetics of hepatic monoacylglycerol acyltransferase in Triton X-100 mixed micelles.

In order to gain a better understanding of the kinetics of activation and inhibition of hepatic monoacylglycerol acyltransferase (MGAT) (EC 2.3.1.22) by fatty acid, we examined the effect of fatty acid with respect to MGAT's long-chain acyl-CoA substrate in Triton X-100 mixed micelles. At concentrations between 2.5 and 5.3 mol %, oleic acid stimulated MGAT activity 2-fold, whereas oleic acid inhibited MGAT at concentrations higher than 7.5 mol %. The dependence on palmitoyl-CoA was highly cooperative with a Hill constant of greater than 2.4. When present at less than 3 mol%, oleic acid eliminated the lag in the dependence curve. When concentrations of oleic acid were higher than 3 mol %, Michaelis-Menton kinetics were observed with an apparent k(m) value of about 54 microM for palmitoyl-CoA but with progressively decreasing Vmax values. This effect was not observed with octanoic acid, suggesting that the medium-chain fatty acid is unable to associate stably with the mixed micelle and, thus, cannot substantially alter substrate affinity. When anionic phospholipids were tested, phosphatidic acid, lysophosphatidic acid, phosphatidylserine, and phosphatidylinositol eliminated some of the lag in activation by palmitoyl-CoA. At high molar concentrations of the anionic lipid activators, apparent k(m) values ranged from 77 microM for phosphatidic acid to 196 microM for phosphatidylinositol. Zwitterionic phospholipids had no effect, nor did the non-phospholipid activators bovine serum albumin or sn-1,2-diacylglycerol. CaCl2, but not neomycin or KC1, could overcome the inhibitory effect of oleic acid; thus, the inhibitory effect of fatty acid did not appear to occur by electrostatic interactions. These blockers did not change the effects observed with the anionic phospholipid activators or with the inhibitor, sphingosine. An altered k(m) for palmitoyl-CoA in the presence of fatty acid or anionic phospholipid suggests that both long-chain fatty acids and phospholipid cofactors may induce a conformational change in MGAT, thereby altering the enzyme's affinity for its long-chain acyl-CoA substrate. These data further support the hypothesis that the synthesis of glycerolipids via the monoacylglycerol pathway may be highly regulated via a variety of lipid second messengers such as phosphatidic acid and diacylglycerol, as well as by the influx of fatty acids derived from high-fat diets, or from the hydrolysis of adipocyte triacylglycerol during fasting or diabetes.

Acyltransferases↗
PubMed1996

Interaction of calmodulin-binding domain peptides of nitric oxide synthase with membrane phospholipids: regulation by protein phosphorylation and Ca(2+)-calmodulin.

Endothelial nitric oxide synthase (eNOS) is unique among the NO synthase isozymes in being modified with myristoyl group, which appears to be necessary for its membrane association. However, the presence of myristoylated eNOS in cytosolic fraction after the stimulation-dependent translocation of the enzyme from membrane to cytosol suggests that other regions may be involved in the eNOS-membrane interaction and its regulation. In this study, we have synthesized a 20-amino acid peptide corresponding to the putative calmodulin-binding domain of human eNOS and studied the interaction of the peptide with calmodulin and with various membrane phospholipids. The peptide formed a stoichiometric complex with calmodulin. Upon addition of various acidic phospholipids, the peptide showed a drastic conformational change from random coil to alpha-helix, as was evidenced by circular dichroism spectroscopy. These results suggest that the same domain of eNOS binds both calmodulin and membrane phospholipids. Furthermore, we found that the synthetic peptide was phosphorylated in vitro by protein kinase C. Phosphorylation of the peptide decreased its interaction with membrane phospholipids. Thus, our results raise the possibility that the calmodulin-binding domain is directly involved in the membrane association of eNOS and that phosphorylation of the domain and Ca(2+)-calmodulin may regulate the interaction. Synthetic peptides corresponding to the calmodulin-binding domains of macrophage and neuronal isozymes showed similar abilities to bind phospholipids, suggesting that the calmodulin-binding domains of NO synthase serve as the phospholipid-binding domains as well.

Amino Acid Sequence↗
PubMed1998

Release of phospholipids from erythrocyte membranes by taurocholate is determined by their transbilayer orientation and hydrophobic backbone.

Bile salts mediate a specific release of phosphatidylcholine (PC) from the canalicular membrane into the bile fluid. We utilized human red blood cells (RBC) as a model system to study the release of endogenous phospholipids as well as phospholipid analogues from plasma membranes in the presence of the bile salt taurocholate (TC). Short- and long-chain fluorescent as well as spin-labeled analogues with various headgroups were chosen. RBC were labeled either on the exoplasmic or on the cytoplasmic leaflet with the analogues and incubated with various concentrations of TC. Analogues on the exoplasmic layer could be readily released by TC. Release was most efficient above the critical micellar concentration (CMC) of TC. Release was independent of the headgroup, but depended on the fatty acid chain length of the analogues; i.e., it was lower for long-chain than for short-chain labeled phospholipids. Analogues on the cytoplasmic leaflet were efficiently shielded from TC-mediated release. The preferential release of endogenous PC and sphingomyelin (SM) from the erythrocyte membrane above the CMC supports the conclusion that TC-mediated release of phospholipids occurs preferentially from the exoplasmic leaflet independent of their headgroup. However, the extent of release of endogenous phospholipids was significantly lower in comparison to that of analogues, endorsing the relevance of the hydrophobic backbone for bile salt mediated release of phospholipids. Implications for the mechanism of the release of PC from the canalicular membrane into the bile fluid are discussed.

Bile↗
PubMed1999

Electrostatic interactions during acidic phospholipid reactivation of DnaA protein, the Escherichia coli initiator of chromosomal replication.

The initiation of Escherichia coli chromosomal replication by DnaA protein is strongly influenced by the tight binding of the nucleotides ATP and ADP. Anionic phospholipids in a fluid bilayer promote the conversion of inactive ADP-DnaA protein to replicatively active ATP-DnaA protein in vitro, and thus likely play a key role in regulating DnaA activity. Previous studies have revealed that, during this reactivation, a specific region of DnaA protein inserts into the hydrophobic portion of the lipid bilayer in an acidic phospholipid-dependent manner. To elucidate the requirement for acidic phospholipids in the reactivation process, the contribution of electrostatic forces in the interaction of DnaA and lipid was examined. DnaA-lipid binding required anionic phospholipids, and DnaA-lipid binding as well as lipid-mediated release of DnaA-bound nucleotide were inhibited by increased ionic strength, suggesting the involvement of electrostatic interactions in these processes. As the vesicular content of acidic phospholipids was increased, both nucleotide release and DnaA-lipid binding increased in a linear, parallel manner. Given that DnaA-membrane binding, the insertion of DnaA into the membrane, and the consequent nucleotide release all require anionic phospholipids, the acidic headgroup may be necessary to recruit DnaA protein to the membrane for insertion and subsequent reactivation for replication.

Bacterial Proteins↗
PubMed2002

Selective sterol-phospholipid associations in fluid bilayers.

The nearest-neighbor preferences of three exchangeable lipid monomers (two phospholipids that differ in length, A and B, and a derivative of cholesterol, C) have been quantified in the fluid bilayer state by use of the nearest-neighbor recognition method (Davidson, S. K. M.; Regen, S. L. Chem. Rev. 1997, 97, 1269). Thus, an analysis of the equilibrium dimer distributions has shown that (i) the sterol favors both phospholipids as nearest neighbors relative to other sterol molecules, (ii) that this recognition is selective (i.e., the sterol favors the longer phospholipid as a nearest neighbor over the shorter one, especially when the sterol concentrations in the bilayer is high (e.g., 40 mol %), and (iii) the phospholipids, themselves, are unable to recognize each other. Taken together, these findings indicate that the probable mechanism by which cholesterol induces homoassociation of A and B in analogous bilayers is one in which the sterol "pulls" two or more of the longer phospholipid monomers (B) out of a "sea" of randomly mixed A and B. These findings also lend support for the notion of cholesterol-phospholipid complexation in fluid bilayers. The biological implications of these findings are briefly discussed.

Cholesterol↗
PubMed2003

Oxidatively truncated docosahexaenoate phospholipids: total synthesis, generation, and Peptide adduction chemistry.

The recent immunological detection of extraordinarily high levels of carboxyethylpyrrole (CEP) modifications of proteins from the retinas of individuals with age-related macular degeneration provided presumptive evidence for the involvement of docosahexaenoate-derived oxidatively truncated phospholipids in retinal pathology. To facilitate the in vivo detection and characterization of the chemistry and biological activities of these postulated naturally occurring molecules, a family of oxidatively truncated phospholipids was prepared by total syntheses. Their formation in oxidation reactions of a docosahexaenoate ester of 2-lysophosphatidylcholine (DHA-PC) was also demonstrated. Free radical-induced oxidative cleavage of DHA-PC promoted by myeloperoxidase or copper ions generates similar mixtures of these phospholipids. The most abundant products were 1-palmitoyl-2-succinoyl-sn-glycero-3-phosphatidylcholine (4.7%) and 2-(6-carboxy-4-oxohex-5-enoyl)-1-palmitoyl-sn-glycero-3-phosphatidylcholine (1.7%). Both of these oxidatively truncated phospholipids are homologues of biologically active arachidonate-derived phospholipids. A minor product from DHA-PC, 2-(4-hydroxy-7-oxohept-5-enoyl)-1-palmitoyl-sn-glycero-3-phosphatidylcholine (0.4% yield), reacted with the epsilon-amino group of a peptide lysyl residue to produce a CEP derivative in 0.7% yield. These observations support the previous conclusion, based on immunological evidence, that CEPs are generated by the reaction of an oxidatively truncated phospholipid with proteins in the retina and further indicate that CEP protein modifications probably represent only a tiny fraction of the products generated upon oxidative damage of DHA-PC in photoreceptor disk membranes.

Combinatorial Chemistry Techniques↗
PubMed2007

Lateral intermolecular forces between biomembrane lipids in two dimensions: 1,2-dipalmitin at the heptane/water interface compared with phospholipids.

The lateral interaction forces between phospholipids in two-dimensional arrays are fundamental to understanding membrane biophysics. In previous studies the related thermodynamic functions have been measured for spread phospholipid monolayers at the oil/water interface over a range of temperatures and densities, and the two-dimensional virial coefficients obtained. These coefficients have been computed from a model that emphasizes the head group zwitterion interactions. In this study we examine the contribution of the diglyceride portion of phospholipid molecules to the lateral intermolecular forces. Measurements of the heptane/water interfacial tension as a function of the concentration of 1,2-dipalmitoyl glycerol (DP) in the heptane were made over a range of low surface pressures at 25 degrees C. Infrared measurements on the DP solutions show that the solutions are ideal. The results are interpreted to give two-dimensional virial coefficients for the adsorbed monolayer. The second virial coefficient B2(T) for DP is +0.31 nm2/molecule, in marked contrast to the much larger positive values found for the corresponding phospholipids at the same interface and temperature, and clearly indicating an attractive component to the lateral potentials of mean force between pairs of DP molecules. The contribution of the diglyceride moiety to the pair potentials of the phospholipids thus appears to be minor but not negligible. The differences in the second virial coefficients for DP and the phospholipids are interpreted primarily in terms of the orientation of the ester carbonyl dipoles, also drawing on spectroscopic and diffraction evidence from related structures.

Chemistry, Physical↗
PubMed1996

Effects of phospholipids on the in vitro percutaneous penetration of prednisolone and analysis of mechanism by using attenuated total reflectance-Fourier transform infrared spectroscopy.

We investigated the effects of 10 phospholipids on the in vitro percutaneous penetration of prednisolone (PR) through the dorsal skin of guinea pigs. A marked enhancing effect of PR penetration was observed in the presence of phospholipids that have unsaturated acyl chains. A maximum of 68-fold enhancement was observed compared to that of control. On the contrary, phospholipids that have saturated acyl chains did not significantly increase the amount of PR passing to the receptor side. Attenuated total reflectance-Fourier transform infrared spectroscopy was used to monitor the outer several microns of stratum corneum (SC) surface. It was observed that phospholipids that have unsaturated acyl chains induced higher and broader absorbance shifts in the C-H bond stretching region while phospholipids that have saturated acyl chains induced lower and sharper absorbance shifts in the C-H bond stretching region. A significant parallel between the amount of PR penetrated and the lipid-chain fluidity of the SC was found. These results suggest that phospholipids may influence the percutaneous penetration of PR by changing the lipid-chain fluidity of the SC.

Animals↗
PubMed2004

Incorporation of glycoconjugated porphyrin derivatives into phospholipid monolayers: a screening method for the evaluation of their interaction with a cell membrane.

The use of porphyrin derivatives in photodynamic therapy is of excellent prospect for the treatment of superficial or easily reachable tumors. The selection of porphyrin derivatives by tumor cells depends to a large extent of their ability to interact with the biological membrane. The evaluation of porphyrin interaction with phospholipids can thus be used as a screening method. In this work we report on the assessment of the interaction of three new porphyrin derivatives with various phospholipids forming Langmuir films by surface tension and surface pressure measurements, grazing incidence X-ray diffraction, and liquid chromatography on an IAM stationary phase. The results show that the hydroxylated phenylporphyrin (m-THPP) is able to interact with all studied phospholipids and to significantly disorganize the structure of their monolayers. Obviously, the interaction occurs at the level of the hydrophobic chains of a phospholipid. A triglucoconjugated phenylporphyrin (m-TPP(Glu)3) also interacts with the phospholipids though to a lesser extent. Conversely, the tetraglucoconjugated derivative (m-TPP(Glu)4) exhibits both a weak surface activity and a poor affinity for the studied phospholipids. Thus, whereas m-THPP and m-TPP(Glu)3 are expected to penetrate into a biological membrane, m-TPP(Glu)4 seems unlikely to do so.

Cell Membrane↗