Study of calix[4]resorcinarene-dopamine complexation in mixed phospholipid monolayers formed at the air-water interface

We have studied the physical properties of monolayers formed by calix[4]resorcinarene and in mixtures with dipalmitoyl phosphatidylcholine (DPPC) in various molar ratios formed at the air-water interface and at presence of dopamine in water subphase by means of measurements of surface pressure and dipole potential. We showed that both calix[4]resorcinarene as well as its mixture with DPPC form stable monolayers at the water subphase. The presence of dopamine resulted in an increase of the mean molecular area and in a decrease of the compressibility modulus of the monolayers. For mixed monolayers at higher content of calix[4]resorcinarene (> 0.2 molar fraction) a deviation from ideal miscibility took place especially for monolayers in a solid state. This can be connected with formation of aggregates of calix[4] resorcinarene. Lowest miscibility and weakest interaction of dopamine with a monolayer was observed for calix[4]resorcinarene molar fraction of 0.33 in the monolayer.     

Interactions of phospholipid monolayers with carbohydrates

Surface pressure studies of phospholipid monomolecular films of dimyristoylphosphatidylcholine (DMPC) and dipalmitoylphosphatidylcholine (DPPC) formed at an air/water interface have been made and the effects on the films studied when various carbohydrates are present in the subphase. The results obtained show that at a given temperature, the area per molecule of DPPC increases with increasing concentration of the carbohydrate in the subphase. The carbohydrate which has the greatest expanding effect on the phospholipid monolayer is glycerol, followed in turn by trehalose, sucrose, glucose, raffinose, and inositol. The mechanism of monolayer expansion by glycerol is different from that observed in other carbohydrates, as the following experiments demonstrate. Below the phase transition temperature of DPPC, the area per molecule of DPPC at a pressure of 12.5 dyn/cm is the same with and without glycerol in the subphase. However, when the monolayer is heated to a temperature above the phase transition temperature for DPPC, the area/molecule on glycerol is considerably greater than the area/molecule on water at the same surface pressure. Cooling the monolayer back to the lower temperature produces an area/molecule of DPPC which is identical on both water and glycerol subphases. Glycerol therefore has no effect on the low-temperature (condensed) monolayers but causes expansion of the high-temperature (expanded) monolayers. By contrast with glycerol, both trehalose and sucrose interact with the DPPC monolayer producing an increased area/molecule over that observed on water, both with low-temperature (condensed) monolayers and with the high-temperature (expanded) monolayers. The efficiency of these carbohydrates at expanding the monolayer films (with the exception of glycerol) shows a strong correlation with their ability to stabilize membrane structure and function at low water contents.     

Membrane binding of a lipidated N-Ras protein studied in lipid monolayers

The adsorption of doubly lipidated full-length N-Ras protein on 1,2-dipalmitoyl-sn-phosphatidylcholine (DPPC) monolayers was studied by lateral pressure analysis, grazing incidence X-ray diffraction (GIXD), and specular reflectivity (XR). N-Ras protein adsorbs to the DPPC monolayer (lateral pressure of 20 mN/m) from the subphase thereby increasing the lateral pressure in the monolayer by 4 mN/m. The protein insertion does not alter the tilt angle and structure of the lipid molecules at the air/water interface but influences the electron density profile of the monolayer. Further, electron density differences into the subphase were observed. The Fresnel normalized reflectivity could be reconstructed in the analysis using box models yielding electron density profiles of the DPPC monolayer in the absence and in the presence of N-Ras protein. The electron density profiles of the DPPC monolayer in the presence of Ras showed clear intensity variations in the headgroup/glycerol/upper chain region, the so-called interface region where previous bilayer studies had confirmed Ras binding. Dedicated to Prof. K. Arnold on the occasion of his 65th birthday.     

A water-soluble calix[4]resorcinarene with L-pipecolinic acid groups as a chiral NMR solvating agent

A sulfonated calix[4]resorcinarene containing L-pipecolinic acid groups is investigated as a water-soluble chiral NMR solvating agent. Aromatic substrates with phenyl, indole, indane, naphthyl, and pyridyl rings are analyzed. The substrates, which are water soluble because of ammonium, hydroxyl, or carboxylate functional groups, form host-guest complexes by insertion of the aromatic ring into the cavity of the calix[4]resorcinarene. Enantiomeric discrimination with the calix[4]resorcinarene derivative with L-pipecolinic acid is compared with similar reagents with proline, hydroxyproline, and α-methylproline moieties that have previously been reported. The derivative with L-pipecolinic acid often produces the best enantiomeric discrimination for one or more hydrogen atoms of the 24 substrates examined herein.     

Miscibility of ternary mixtures of phospholipids and cholesterol in monolayers, and application to bilayer systems

We investigate miscibility transitions of two different ternary lipid mixtures, DOPC/DPPC/Chol and POPC/PSM/Chol. In vesicles, both of these mixtures of an unsaturated lipid, a saturated lipid, and cholesterol form micron-scale domains of immiscible liquid phases for only a limited range of compositions. In contrast, in monolayers, both of these mixtures produce two distinct regions of immiscible liquid phases that span all compositions studied, the alpha-region at low cholesterol and the beta-region at high cholesterol. In other words, we find only limited overlap in miscibility phase behavior of monolayers and bilayers for the lipids studied. For vesicles at 25 degrees C, the miscibility phase boundary spans portions of both the monolayer alpha-region and beta-region. Within the monolayer beta-region, domains persist to high pressures, yet within the alpha-region, miscibility phase transition pressures always fall below 15 mN/m, far below the bilayer equivalent pressure of 32 mN/m. Approximately equivalent phase behavior is observed for monolayers of DOPC/DPPC/Chol and for monolayers of POPC/PSM/Chol. As expected, pressure-area isotherms of our ternary lipid mixtures yield smaller molecular area and compressibility for monolayers containing more saturated acyl chains and cholesterol. All monolayer experiments were conducted under argon. We show that exposure of unsaturated lipids to air causes monolayer surface pressures to decrease rapidly and miscibility transition pressures to increase rapidly.     

Modifying dipalmitoylphosphatidylcholine monolayers by n-hexadecanol and dipalmitoylglycerol

The monolayer structure of pure dipalmitoylphosphatidylcholine (DPPC) and equimolar mixtures of DPPC/n-hexadecanol (C(16)OH) and DPPC/dipalmitoylglycerol (DPG) are studied by the film balance technique and grazing incidence X-ray diffraction measurements. At 20 degrees C, the binary systems exhibit complete miscibility. In contrast to pure DPPC monolayers, a condensing effect is observed in the presence of both non-phospholipid additives; but the phase transition behavior differs. The tilt angle of the hydrocarbon chains in the DPPC/C(16)OH mixture is significantly smaller than in pure DPPC monolayers. The tilt of the chains is even further reduced in the mixed monolayer of DPPC/DPG. A comparison of the three systems reveals distinct structural features such as phase state, chain tilt, and molecular area over a wide range of surface pressures. Therefore, these monolayers provide a highly suitable model to investigate the influence of structural parameters on biological processes occurring at the membrane surface, e.g. enzymatic reactions and adsorption events.     

Differential effects of surfactant protein A on regional organization of phospholipid monolayers containing surfactant protein B or C

Epifluorescence microscopy combined with a surface balance was used to study monolayers of dipalmitoylphosphatidylcholine (DPPC)/egg phosphatidylglycerol (PG) (8:2, mol/mol) plus 17 wt % SP-B or SP-C spread on subphases containing SP-A in the presence or absence of 5 mM Ca(2+). Independently of the presence of Ca(2+) in the subphase, SP-A at a bulk concentration of 0.68 microg/ml adsorbed into the spread monolayers and caused an increase in the molecular areas in the films. Films of DPPC/PG formed on SP-A solutions showed a pressure-dependent coexistence of liquid-condensed (LC) and liquid-expanded (LE) phases. Apart from these surface phases, a probe-excluding phase, likely enriched in SP-A, was seen in the films between 7 mN/m < or = pi < or = 20 mN/m. In monolayers of SP-B/(DPPC/PG) spread on SP-A, regardless of the presence of calcium ions, large clusters of a probe-excluding phase, different from probe-excluding lipid LC phase, appeared and segregated from the LE phase at near-zero surface pressures and coexisted with the conventional LE and LC phases up to approximately 35 mN/m. Varying the levels of either SP-A or SP-B in films of SP-B/SP-A/(DPPC/PG) revealed that the formation of the probe-excluding clusters distinctive for the quaternary films was influenced by the two proteins. Concanavalin A in the subphase could not replace SP-A in its ability to modulate the textures of films of SP-B/(DPPC/PG). In films of SP-C/SP-A/(DPPC/PG), in the absence of calcium, regions consisting of a probe-excluding phase, likely enriched in SP-A, were detected at surface pressures between 2 mN/m and 20 mN/m in addition to the lipid LE and LC phases. Ca(2+) in the subphase appeared to disperse this phase into tiny probe-excluding particles, likely comprising Ca(2+)-aggregated SP-A. Despite their strikingly different morphologies, the films of DPPC/PG that contained combinations of SP-B/SP-A or SP-C/SP-A displayed similar distributions of LC and LE phases with LC regions occupying a maximum of 20% of the total monolayer area. Combining SP-A and SP-B reorganized the morphology of monolayers composed of DPPC and PG in a Ca(2+)-independent manner that led to the formation of a separate potentially protein-rich phase in the films.     

The interaction of liposomes containing intrinsic erythrocyte membrane proteins with lipid monolayers at air/water and oil/water interfaces

The main intrinsic membrane proteins of the human erythrocyte membrane, glycophorin and the anion transporter, were isolated by extraction with Triton X-100 and ion-exchange chromatography. After removal of detergent the extract consisted of proteolipid vesicles with a lipid:protein molar ratio in the range 50-60 and a diameter of the order of 200 nm. The interaction between these vesicles and dipalmitoylphosphatidylcholine (DPPC), cholesterol and cholesterol:DPPC (2:1 molar ratio) monolayers at air/water and n-decane/water interfaces has been studied. The vesicles interact with the monolayers, rapidly causing large increases in surface pressure. Limiting values of surface pressure, 39.4-43 mN . m-1 at air/water and 31.5-33.4 mN . m-1 at the n-decane/water interface, were reached at protein levels above 1 microgram . ml-1. At the air/water interface, and probably at the n-decane/water, surface pressure increases were limited by monolayer collapse. Compression isotherms and surface potential measurements indicated that material from the proteolipid vesicles entered the monolayer phase. In contrast to proteolipid vesicles, injection of protein-free liposomes beneath the monolayer resulted in smaller, slower increases in surface pressure. Thus, the presence of intrinsic membrane proteins in vesicles greatly facilitated the transfer of material into the lipid monolayer.     

Conformational changes of the lecithin headgroup in monolayers at the air/water interface

The headgroup conformation of the phospholipid dipalmitoyl-glycero-phosphocholine (DPPC) in monolayers at the air/water interface has been studied by neutron reflection in the fluid like liquid-expanded (LE) and in the crystal like solid (S) phase. Information on the headgroup conformation in the two phases has been obtained by scattering contrast variation of the lipid monolayer using four differently deuterated species of DPPC: perdeuterated, chain perdeuterated, choline group perdeuterated and selectively headgroup deuterated. Since the measurements were done mainly on a subphase of null reflecting water (i.e. water scattering contrast matched to the air) there is no subphase contribution to reflectivity and the simplest one layer model can be employed for the data analysis, thus minimising the number of free parameters. A remarkable change of the headgroup orientation was observed between the LE and the S phase. We found that the phosphate-nitrogen dipole of the DPPC headgroup exhibits an in-plane orientation with respect to the monolayer in the LE phase but it assumes a more parallel orientation to the surface normal at lateral pressures above 30 mN/m (S phase). Moreover, this conformational change is accompanied by a significant alteration of the headgroup hydration.Abbreviations DPPC Dipalmitoyl-Phosphatidylcholine - DMPC Dimyristoyl-Phosphatidylcholine - DPPE Dipalmitoyl-Phosphatidylethanolamine - DMPE Dimyristoyl-Phosphatidylethanolamine - DMPA Dimyristoyl-Phosphatic Acid - DMPG Dimyristoyl-Phosphatidylglycerol Correspondence to: T M. Bayed     

Lipid compositional analysis of pulmonary surfactant monolayers and monolayer-associated reservoirs

Pulmonary surfactant is a lipid:protein complex containing dipalmitoyl-phosphatidylcholine (DPPC) as the major component. Recent studies indicate adsorbed surfactant films consist of a surface monolayer and a monolayer-associated reservoir. It has been hypothesized that the monolayer and its functionally contiguous reservoir may be enriched in DPPC relative to bulk phase surfactant. We investigated the compositional relationship between the monolayer and its reservoir using paper-supported wet bridges to transfer films from adsorbing dishes to clean surfaces on spreading dishes. Spreading films appear to form monolayers in the spreading dishes. We employed bovine lipid extract surfactant [BLES(chol)] containing [3H]DPPC and either [14C]palmitoyl, oleoyl-phosphatidylcholine (POPC), [14C]dipalmitoyl-phosphatidylglycerol (DPPG), [14C]palmitoyl, oleoyl-phosphatidylglycerol (POPG), or [14C]cholesterol. Radiolabeled phosphatidylglycerols were prepared using phospholipase D. The studies demonstrated that the [3H]DPPC-[14C] POPC ratios were the same in the prepared BLES dispersions as in Langmuir-Blodgett films, indicating a lack of DPPC selectivity during film formation. Furthermore, identical 3H-14C isotopic ratios were observed with DPPC and either 14C-labeled POPC, DPPG, POPG, or cholesterol in the original dispersions, the bulk phases in adsorption dish D1, and monolayers recovered from spreading dish D2. These relationships remained unperturbed with 2-fold increases in bulk concentrations in D1 and 10-fold variations in D1-D2 surface area. These results indicate adsorbed surfactant monolayers and their associated reservoirs possess similar lipid compositions and argue against selective adsorption of DPPC.     

Interaction of poly(ethylene-glycols) with air-water interfaces and lipid monolayers: investigations on surface pressure and surface potential.

We have characterized the surface activity of different-sized poly(ethylene-glycols) (PEG; M(r) 200-100,000 Da) in the presence or absence of lipid monolayers and over a wide range of bulk PEG concentrations (10(-8)-10% w/v). Measurements of the surface potential and surface pressure demonstrate that PEGs interact with the air-water and lipid-water interfaces. Without lipid, PEG added either to the subphase or to the air-water interface forms relatively stable monolayers. Except for very low molecular weight polymers (PEGs < 1000 Da), low concentrations of PEG in the subphase (between 10(-5) and 10(-4)% w/v) increase the surface potential from zero (with respect to the potential of a pure air-water interface) to a plateau value of approximately 440 mV. At much higher polymer concentrations, > 10(-1)% (w/v), depending on the molecular weight of the PEG and corresponding to the concentration at which the polymers in solution are likely to overlap, the surface potential decreases. High concentrations of PEG in the subphase cause a similar decrease in the surface potential of densely packed lipid monolayers spread from either diphytanoyl phosphatidylcholine (DPhPC), dipalmitoyl phosphatidylcholine (DPPC), or dioleoyl phosphatidylserine (DOPS). Adding PEG as a monolayer at the air-water interface also affects the surface activity of DPhPC or DPPC monolayers. At low lipid concentration, the surface pressure and potential are determined by the polymer. For intermediate lipid concentrations, the surface pressure-area and surface potential-area isotherms show that the effects due to lipid and PEG are not always additive and that the polymer's effect is distinct for the two lipids. When PEG-lipid-mixed monolayers are compressed to surface pressures greater than the collapse pressure for a PEG monolayer, the surface pressure-area and surface potential-area isotherms approach that of the lipid alone, suggesting that for this experimental condition PEG is expelled from the interface.     

Influence of vitamin C on alcohol binding to phospholipid monolayers

The simple model of the biological membrane is provided by well-controlled lipid monolayers at the air-water interface. The Maxwell displacement current technique (MDC) provides novel approach to conformation study of the membrane models. The effect of alcohols is interaction with membrane molecules, mainly with the lipid head group and consequent changes in physical-chemical properties of the membrane. The aim of study is to detect changes in structural, electrical and mechanical properties of dipalmitoyl-phosphatidylcholine (DPPC) monolayer on the subphase of methanol-water and ethanol-water mixtures before and after addition of antioxidant agent, vitamin C. Monolayers properties are investigated by a surface pressure analysis (including mechanical properties evaluation) and the Maxwell displacement current measurement, the dipole moment projection calculation. Surface pressure-area isotherms show similar behaviour of the DPPC monolayer on alcohol-water mixtures independently on presence of vitamin C. Binding/adsorption process induces change of electron density distribution across monolayer and thus the molecular dipole moment. We observe small or negligible binding of methanol molecules on oxygen bonds of DPPC. Thus the antioxidant, vitamin C, has no significant effect. For ethanol-water mixtures is observed recovery of electrical properties in presence of antioxidant agent. We suppose that vitamin C regulates DPPC-ethanol molecules interaction.     

Surfactant protein A forms extensive lattice-like structures on 1,2-dipalmitoylphosphatidylcholine/rough-lipopolysaccharide-mixed monolayers

Due to the inhalation of airborne particles containing bacterial lipopolysaccharide (LPS), these molecules might incorporate into the 1,2-dipalmitoylphosphatidylcholine (DPPC)-rich monolayer and interact with surfactant protein A (SP-A), the major surfactant protein component involved in host defense. In this study, epifluorescence microscopy combined with a surface balance was used to examine the interaction of SP-A with mixed monolayers of DPPC/rough LPS (Re-LPS). Binary monolayers of Re-LPS plus DPPC showed negative deviations from ideal behavior of the mean areas in the films consistent with partial miscibility and attractive interaction between the lipids. This interaction resulted in rearrangement and reduction of the size of DPPC-rich solid domains in DPPC/Re-LPS monolayers. The adsorption of SP-A to these monolayers caused expansion in the lipid molecular areas. SP-A interacted strongly with Re-LPS and promoted the formation of DPPC-rich solid domains. Fluorescently labeled Texas red-SP-A accumulated at the fluid-solid boundary regions and formed networks of interconnected filaments in the fluid phase of DPPC/Re-LPS monolayers in a Ca(2+)-independent manner. These lattice-like structures were also observed when TR-SP-A interacted with lipid A monolayers. These novel results deepen our understanding of the specific interaction of SP-A with the lipid A moiety of bacterial LPS.     

Interaction of lipid vesicles with monomolecular layers containing lung surfactant proteins SP-B or SP-C

Pulmonary surfactant contains two families of hydrophobic proteins, SP-B and SP-C. Both proteins are thought to promote the formation of the phospholipid monolayer at the air-fluid interface of the lung. The Wilhelmy plate method was used to study the involvement of SP-B and SP-C in the formation of phospholipid monolayers. The proteins were either present in the phospholipid vesicles which were injected into the subphase or included in a preformed phospholipid monolayer. In agreement with earlier investigators, we found that SP-B and SP-C, present in phospholipid vesicles, were able to induce the formation of a monolayer, as became apparent by an increase in surface pressure. However, when the proteins were present in a preformed phospholipid monolayer (20 mN/m) at similar lipid to protein ratios, the rate of surface pressure increase after injection of pure phospholipid vesicles into the subphase at similar vesicle concentrations was 10 times higher. The process of phospholipid insertion from phospholipid vesicles into the protein-containing monolayers was dependent on (1) the presence of (divalent) cations, (2) the phospholipid concentration in the subphase, (3) the size of the phospholipid vesicles, (4) the protein concentration in the preformed monolayer, and (5) the initial surface pressure at which the monolayers were formed. Both in vesicles and in preformed monolayers, SP-C was less active than SP-B in promoting the formation of a phospholipid monolayer. The use of preformed monolayers containing controlled protein concentrations may allow more detailed studies on the mechanism by which the proteins enhance phospholipid monolayer formation from vesicles.     

Interaction of long-chain nicotinates with dipalmitoylphosphatidylcholine

The interaction of four long-chain nicotinates, compounds that are of interest as potential chemopreventive agents, with dipalmitoylphosphatidylcholine (DPPC) was investigated in monolayers at the air-water interface and in fully hydrated bilayers. For the monolayer studies, the compression isotherms of mixtures of the respective nicotinate with DPPC were recorded at various compositions on a hydrochloric acid subphase (pH 1.9-2.1, 37 +/- 2 degrees C). The headgroup of the nicotinates (24-29 A2/molecule) is larger than that of the hydrophobic tail (20 A2/molecule). The pure nicotinates exhibit a temperature- and chain length-dependent transition from an expanded to a condensed phase. Analysis of the concentration dependence of the average molecular area at constant film pressure and the concentration dependence of the breakpoint of the phase transition from the expanded to the condensed state suggests that all four DPPC-nicotinate mixtures are partially miscible at the air-water interface. Although a complex phase behavior with several phase transitions was observed, differential scanning calorimetry studies of the four mixtures are also indicative of the partial miscibility of DPPC and the respective nicotinate. Overall, the complex phase behavior most likely results from the head-tail mismatch of the nicotinates and the geometric packing constraints in the two-component lipid bilayer.     

The influence of plant hormones on phospholipid monolayer stability

The influence of hormones in water subphase on the stability of monolayers built of phospholipid mixtures extracted from embryogenic (PLE) and nonembryogenic (PLNE) wheat calli was examined. Additionally, experiments on individual lipids, dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidic acid (DPPA), were performed. DPPC was chosen because it was the main phospholipid present in both calli. Negatively charged DPPA could mimic a negatively charged natural mixture of lipids. As hormones, auxins (IAA and 2,4-D), cytokinins (zeatin and kinetin) and zearalenone were chosen. The time of monolayer stability for PLNE calli was much longer than for PLE calli. Kinetics of monolayer stability of PLNE was similar to DPPA, whereas that of PLE was similar to DPPC. Generally, hormones increased the time after which the monolayer stability was reached and decreased the surface pressure. The greatest effect was observed for auxins (especially IAA), whereas cytokinins affected the monolayer stability to a lesser degree.     

Proton transport at the monolayer-water interface.

It is shown that when monolayers of stearic acid, palmitic acid, DPPC, or DPPS are compressed above some critical area Ac a lateral conduction mechanism is initiated at the monolayer/water interface. The interfacial conductance increases on further increasing the molecular packing density in the monolayer. All compounds also show major changes in surface potential at Ac the potential becoming more positive in all cases. It is argued that this is a consequence of structural reorganisation at the headgroup/water interface causing a significant reduction in the local permittivity. The critical area, Ac, is approximately double the molecular areas estimated from the pressure-area isotherm, and experiments with stearic acid monolayers show that Ac decreases significantly when the chaotropic ion SCN-, which is known to disrupt the molecular structure of water, is added to the subphase. It is likely, therefore, that the structural changes occurring at Ac involve the formation of a hydrogen bonded network between monolayer headgroups and adjacent water molecules at the monolayer/water interface. It is suggested that the conduction mechanism initiated at Ac arises from proton hopping along this hydrogen-bond network.     

Dipalmitoylphosphatidylcholine and cholesterol in monolayers spread from adsorbed films of pulmonary surfactant

Pulmonary surfactant forms a surface film that consists of a monolayer and a monolayer-associated reservoir. The extent to which surfactant components including the main component, dipalmitoylphosphatidylcholine (DPPC), are adsorbed into the monolayer, and how surfactant protein SP-A affects their adsorptions, is not clear. Transport of cholesterol to the surface region from dispersions of bovine lipid extract surfactant [BLES(chol)] with or without SP-A at 37 degrees C was studied by measuring surface radioactivities of [4-(14)C]cholesterol-labeled BLES(chol), and the Wilhelmy plate technique was used to monitor adsorption of monolayers. Results showed that transport of cholesterol was lipid concentration dependent. SP-A accelerated lipid adsorption but suppressed the final level of cholesterol in the surface. Surfactant adsorbed from a dispersion with or without SP-A was transferred via a wet filter paper to a clean surface, where the surface radioactivity and surface tension were recorded simultaneously. It was observed that 1) surface radioactivity was constant over a range of dispersion concentrations; 2) cholesterol and DPPC were transferred simultaneously; and 3) SP-A limited transfer of cholesterol.These results indicate that non-DPPC components of pulmonary surfactant can be adsorbed into the monolayer. Studies in the transfer of [1-(14)C]DPPC-labeled BLES(chol) to an equal or larger clean surface area revealed that SP-A did not increase selective adsorption of DPPC into the monolayer. Evaluation of transferred surfactant with a surface balance indicated that it equilibrated as a monolayer. Furthermore, examination of transferred surfactants from dispersions with and without prespread BLES(chol) monolayers revealed a functional contiguous association between adsorbed monolayers and reservoirs.     

Asymmetric lipid bilayer formation stabilized by DNA at the air/water interface

The lipid bis(guanidinium)-tren-cholesterol (BGTC) is a cationic cholesterol derivative bearing guanidinium polar headgroups used for gene transfection either alone or formulated as liposomes with the zwitterionic lipid 1,2-di-[cis-9-octadecenoyl]-sn-glycero-3-phosphoethanolamine (DOPE). Previous investigations have shown its ability to strongly interact with DNA and form asymmetric lipid bilayers at the air/water interface when mixed with DOPE. Here, with a view to further investigate its physicochemical behavior, we studied the interactions of mixtures of BGTC with another zwitterionic lipid, 1,2-Dimyristoyl-sn-Glycero-3-Phosphocholine, (DMPC), with DNA at the air/water interface by using the Langmuir monolayer technique coupled with Brewster Angle Microscopy (BAM) and Polarization Modulation Infra Red Reflexion Absorption (PMIRRAS) spectroscopy and we investigate DNA–BGTC/DMPC interactions. We demonstrate that when DNA is injected into the subphase in excess compared to the positive charges of BGTC, it adsorbs to BGTC/DMPC monolayers at 20 mN/m whatever the lipid monolayer composition (1/5, 2/3 or 3/2 BGTC/DMPC molar ratio) and forms an incomplete monolayer of either isotropic or anisotropic double strands depending on the BGTC content in the monolayer. Compression beyond the collapse of some mixed DNA–BGTC/DMPC (2/3 and 3/2 molar ratio) systems leads to the formation of DNA monolayers underneath asymmetric lipid bilayers characterized by a bottom layer of BGTC in contact with DNA and a top layer mainly constituted of DMPC.