Stimuli-responsive surfactant/phospholipid stabilized colloidal dispersions and their film formation

Methyl methacrylate (MMA) and n-butyl acrylate (nBA) were copolymerized into stable colloidal particles in the presence of micelle forming sodium dioctyl sulfosuccinate (SDOSS) and liposome forming 1,2-dilauroyl-sn-glycero-3-phosphocholine (DLPC) in aqueous media that serve as thermodynamically stable loci for lipophilic monomers and nanostructured templates. These studies show for the first time that hollow colloidal particles may coalesce to form polymeric films and the combination of SDOSS and DLPC dispersing agents provides a stimuli-responsive environment during film formation through which individual surface stabilizing components can be driven to the film-air (F-A) or film-substrate (F-S) interface. Attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) of p-MMA/nBA colloidal dispersions revealed preferential and enhanced mobility of SDOSS and DLPC lipid rafts to the F-A and F-S interfaces in response to thermal, ionic, and enzymatic stimuli.     

Lectin-recognizable colloidal dispersions stabilized by n-dodecyl beta-D-maltoside: particle-particle and particle-surface interactions

Recently, we reported that it is possible to utilize sugars as stabilizing agents for colloidal particles. This study shows that when n-dodecyl beta-D-maltoside (DDM) is utilized as a dispersing and stabilizing agent in the synthesis and stabilization of poly[methyl methacrylate-co-(n-butyl acrylate)] (p-MMA/nBA) colloidal particles, stable colloidal dispersions can be formed. Since understanding of sugar-protein interactions have numerous practical and scientific implications, these studies examine DDM-stabilized p-MMA/nBA colloidal particles and their specific binding properties with concanavalin A (Con A). By use of spectroscopic analysis, unique binding characteristics that are a function of DDM concentration, time, and the concentration of Con A are detected. When DDM-stabilized p-MMA/nBA particles are allowed to coalesce, DDM is released from the particle surfaces and, under suitable conditions, selectively stratifies in the areas of the excess of interfacial energy near the film-air (F-A) interface, thus providing sites for attracting Con A via alpha-glucose-OH hydrogen bonding. Consequently, adsorption of Con A at the F-A interfaces occur and the degree of adsorption is controlled by the amount of DDM at the F-A interface.     

Film formation from colloidal dispersions stabilized by sugar derivatives and their controllable release for selective protein adsorption

Although the use of sugar and sugar derivatives has been documented in polymer research for many years, there are no reports that would utilize these species as polymerization sites of colloidal polymeric particles that, later on, may be released during particle coalescence to form films with surfaces that differentiate protein adsorption. These studies show that, when n-dodecyl-beta-D-maltoside (DDM) is utilized for the synthesis and stabilization of poly[methyl methacrylate-co-(n-butyl acrylate)] (p-MMA/nBA) colloidal particles, upon particle coalescence DDM stratifies near the film-air (F-A) interface. By using attenuated total reflectance Fourier transform infrared (ATR FT-IR) spectroscopy and internal reflection infrared imaging (IRIRI), comparative adsorption studies on p-MMA/nBA surfaces exposed to globulin (Glo), fibrinogen (Fib), and bovine serum albumin (BSA) reveal that the presence of DDM selectively inhibits Glo and Fib adsorption, but does not affect BSA. The presence of DDM also enhances the rate of mobility of sodium dioctylsulfosuccinate (SDOSS) resulting from interactions between DDM and SDOSS moieties, and the surface morphologies change as a result of concentration variations of DDM in the colloidal dispersions.     

Formation and study of single metal ion-phospholipid complexes in biphasic electrospray ionization mass spectrometry

Single metal ion-phospholipid complexes are observed in biphasic electrospray ionization mass spectrometry (BESI-MS) using a dual-channel microsprayer. Such a microsprayer makes it possible to put into contact two immiscible liquids within the Taylor cone. Thus, L-α-dipalmitoyl phosphatidylcholine (DPPC) dissolved in 1,2-dichloroethane (DCE) reacts with aqueous metal cations (M = Na(+), K(+), Ca(2+), Cu(2+), La(3+)) yielding the formation of [M-DPPC(n)](z+) complexes. The number of phospholipid molecules ranges from 1 to 4 for monovalent ions, to 8 for divalent and to more than 10 for trivalent ions respectively. The large number of ligands observed involves the formation of solvent free single ion-phospholipid complexes.     

A Langmuir film approach to elucidating interactions in lipid membranes: 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine/cholesterol/metal cation systems

The interactions between two membrane lipids, 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine (DPPE) and cholesterol (CHOL), were studied in Langmuir films using surface pressure isotherms and Brewster angle microscopy. The DPPE/CHOL interactions were probed for chosen monolayer and subphase (Na(+), Ca(2+)) composition at 20, 25, and 30 degrees C. The results obtained show that DPPE and CHOL are miscible for the cholesterol mol fractions x(CHOL)=0.3-0.5. Cholesterol induces condensation of the DPPE monolayers. The most significant condensation of the DPPE/CHOL monolayers was observed in the presence of Ca(2+) ions in the subphase at x(CHOL)=0.4. The negative deviation of the molecular surface area (MMA) additivity from the ideal behavior together with negative values of excess free enthalpy of mixing in the monolayers were interpreted in terms of attractive interactions between lipid molecules.     

Erythrocyte ion transport and membrane lipid composition in young and adult rats with NO-deficient hypertension

The aim of our study was to search for abnormalities of sodium and potassium transport in erythrocytes of male Wistar rats subjected to chronic L-NAME treatment (40 mg/kg/day) for 4 weeks either from weaning (4-week-old) or in adulthood (12-week-old). Sodium content, Na(+),K(+)-pump and Na(+),K(+)-cotransport activity, cation leaks as well as membrane cholesterol and phospholipid contents were determined in fresh erythrocytes. Chronic inhibition of NO synthase elicited similar blood pressure rise in both age groups which did not differ in the degree of NO synthase inhibition. No significant ion transport abnormalities were disclosed in erythrocytes of young NO-deficient rats, whereas erythrocyte Na(+) content, outward Na(+),K(+)-cotransport and inward Na(+) leak were significantly reduced in adult hypertensive animals compared to age-matched controls. It should be noted that the erythrocytes of adult control rats were characterized by higher activity of Na(+),K(+)-pump and Na(+),K(+)-cotransport, increased Na(+) and Rb(+) leaks and elevated membrane cholesterol content compared to those of young normotensive controls. Increased Na(+) leak and elevated membrane cholesterol content but reduced membrane phospholipid content were revealed in erythrocytes of adult hypertensive rats when compared to young hypertensive rats. It can be concluded that young and adult Wistar rats did not differ in the extent of NO synthase inhibition and blood pressure rise elicited by chronic L-NAME treatment. Our results exclude the important participation of classical sodium transport abnormalities in the pathogenesis of this NO-deficient form of experimental hypertension.     

Sodium and Other Inorganic Growth Requirements of Bacteroides amylophilus

Bacteroides amylophilus has growth requirements for Na(+), PO(4) (3-), K(+), and small quantities of Mg(2+). No requirement could be shown for Ca(2+) in media previously found growth-yield-limiting for Bacteroides succinogenes. Deletion of Co(2+), Mn(2+), Cl(-), or SO(4) (2-) did not affect growth. Quantitative studies indicate that Na(+), K(+), and PO(4) (3-) have differing effects on the growth of B. amylophilus. A concentration of sodium and potassium ions affects both growth rate and growth yield, whereas a phosphate concentration markedly affects growth yield, but affects growth rate only slightly, if at all. The sodium requirement of B. amylophilus is absolute. It cannot be replaced by K(+), Li(+), Rb(+), or Cs(+). The latter three monovalent cations are toxic to B. amylophilus if supplied to the organism at Na(+)-replacing concentrations. K(+) is inactive at similar concentrations. The K(+) requirement of B. amylophilus may be satisfied by Rb(+). The concentration of Na(+) required by B. amylophilus for abundant growth suggests that B. amylophilus should be considered a slightly halophilic organism. The results suggest that Na(+) may be a more frequent requirement among terrestial bacteria obtained from relatively low-salt environments than has been previously believed.     

Analysis of Na+,K+-ATPase motion and incorporation into the plasma membrane in response to G protein-coupled receptor signals in living cells

Dopamine (DA) increases Na(+),K(+)-ATPase activity in lung alveolar epithelial cells. This effect is associated with an increase in Na(+),K(+)-ATPase molecules within the plasma membrane (). Analysis of Na(+),K(+)-ATPase motion was performed in real-time in alveolar cells stably expressing Na(+),K(+)-ATPase molecules carrying a fluorescent tag (green fluorescent protein) in the alpha-subunit. The data demonstrate a distinct (random walk) pattern of basal movement of Na(+),K(+)-ATPase-containing vesicles in nontreated cells. DA increased the directional movement (by 3.5 fold) of the vesicles and an increase in their velocity (by 25%) that consequently promoted the incorporation of vesicles into the plasma membrane. The movement of Na(+),K(+)-ATPase-containing vesicles and incorporation into the plasma membrane were microtubule dependent, and disruption of this network perturbed vesicle motion toward the plasma membrane and prevented the increase in the Na(+),K(+)-ATPase activity induced by DA. Thus, recruitment of new Na(+),K(+)-ATPase molecules into the plasma membrane appears to be a major mechanism by which dopamine increases total cell Na(+),K(+)-ATPase activity.     

Simultaneous phosphorylation of Ser11 and Ser18 in the alpha-subunit promotes the recruitment of Na(+),K(+)-ATPase molecules to the plasma membrane

Renal sodium homeostasis is a major determinant of blood pressure and is regulated by several natriuretic and antinatriuretic hormones. These hormones, acting through intracellular second messengers, either activate or inhibit proximal tubule Na(+),K(+)-ATPase. We have shown previously that phorbol ester (PMA) stimulation of endogenous PKC leads to activation of Na(+),K(+)-ATPase in cultured proximal tubule cells (OK cells) expressing the rodent Na(+), K(+)-ATPase alpha-subunit. We have now demonstrated that the treatment with PMA leads to an increased amount of Na(+),K(+)-ATPase molecules in the plasmalemma, which is proportional to the increased enzyme activity. Colchicine, dinitrophenol, and potassium cyanide prevented the PMA-dependent stimulation of activity without affecting the increased level of phosphorylation of the Na(+), K(+)-ATPase alpha-subunit. This suggests that phosphorylation does not directly stimulate Na(+),K(+)-ATPase activity; instead, phosphorylation may be the triggering mechanism for recruitment of Na(+),K(+)-ATPase molecules to the plasma membrane. Transfected cells expressing either an S11A or S18A mutant had the same basal Na(+),K(+)-ATPase activity as cells expressing the wild-type rodent alpha-subunit, but PMA stimulation of Na(+),K(+)-ATPase activity was completely abolished in either mutant. PMA treatment led to phosphorylation of the alpha-subunit by stimulation of PKC-beta, and the extent of this phosphorylation was greatly reduced in the S11A and S18A mutants. These results indicate that both Ser11 and Ser18 of the alpha-subunit are essential for PMA stimulation of Na(+), K(+)-ATPase activity, and that these amino acids are phosphorylated during this process. The results presented here support the hypothesis that PMA regulation of Na(+),K(+)-ATPase is the result of an increased number of Na(+),K(+)-ATPase molecules in the plasma membrane.     

Fromation and stoichiometry of a lysozyme-phospholipid-mitochondrial protein ternary complex.

Mitochondrial membranes reconstituted from lipid-depleted mitochondria and aqueous phospholipid dispersions still have the phospholipid negative charges available for ionic interaction with the basic protein, lysozyme. The stoichiometry of the binding is of about 6 nmoles of lysozyme per 100 nmoles of phospholipid in membranes reconstituted with Asolectin, and of 10 nmoles of phospholipid phosphorus in membranes reconstituted with cardiolipin. Unextracted submitochondrial particles ETP also bind lysozyme (about 3 nmoles per 100 nmoles of phospholipid). These observations indicate that the phospholipid anionic groups are not completely shielded by the mitochondrial proteins, which might occupy areas between the nonpolar groups of the lipid molecules.     

ERK1/2 mediates insulin stimulation of Na(+),K(+)-ATPase by phosphorylation of the alpha-subunit in human skeletal muscle cells

Insulin stimulates Na(+),K(+)-ATPase activity and induces translocation of Na(+),K(+)-ATPase molecules to the plasma membrane in skeletal muscle. We determined the molecular mechanism by which insulin regulates Na(+),K(+)-ATPase in differentiated primary human skeletal muscle cells (HSMCs). Insulin action on Na(+),K(+)-ATPase was dependent on ERK1/2 in HSMCs. Sequence analysis of Na(+),K(+)-ATPase alpha-subunits revealed several potential ERK phosphorylation sites. Insulin increased ouabain-sensitive (86)Rb(+) uptake and [(3)H]ouabain binding in intact cells. Insulin also increased phosphorylation and plasma membrane content of the Na(+),K(+)-ATPase alpha(1)- and alpha(2)-subunits. Insulin-stimulated Na(+),K(+)-ATPase activation, phosphorylation, and translocation of alpha-subunits to the plasma membrane were abolished by 20 microm PD98059, which is an inhibitor of MEK1/2, an upstream kinase of ERK1/2. Furthermore, inhibitors of phosphatidylinositol 3-kinase (100 nm wortmannin) and protein kinase C (10 microm GF109203X) had similar effects. Notably, insulin-stimulated ERK1/2 phosphorylation was abolished by wortmannin and GF109203X in HSMCs. Insulin also stimulated phosphorylation of alpha(1)- and alpha(2)-subunits on Thr-Pro amino acid motifs, which form specific ERK substrates. Furthermore, recombinant ERK1 and -2 kinases were able to phosphorylate alpha-subunit of purified human Na(+),K(+)-ATPase in vitro. In conclusion, insulin stimulates Na(+),K(+)-ATPase activity and translocation to plasma membrane in HSMCs via phosphorylation of the alpha-subunits by ERK1/2 mitogen-activated protein kinase.     

Dielectric properties of spherical macroion suspensions. I. Study on monodisperse polystyrene latex

Dielectric properties of polystyrene latex suspended in aqueous media are investigated with special attention to the effect of volume fraction of the latex and salt concentration. The experimental data show the existence of two dispersions, one in the low-frequency range from 10(3) to 10(5) Hz. and the other in the high-frequcncy range from 10(5) to 10(7) Hz. In the salt-free system. both dispersions are of the Debye type and their relaxation limes arc insensitive to the volume fraction. Addition of H2SO4 to the suspension enlarges the magnitude of the low-frequency dispersion and reduces that of the high-frequency dispersion. whereas it does not affect the relaxation times. In the mixture of two species of counterions, e.g. H+ and Na(+), the low-frequency dispersion deviates from the Debye type. while the high-frequency dispersion docs not. From these facts, the high- and low-frequency dispersions are thought to be due to the radial and tangential components of the displacement current at the surface of the latex. The latter process is consistent with the Schwarz theory of the dielectric dispersion of colloidal suspensions.     

Methylene blue prevents methylmalonate-induced seizures and oxidative damage in rat striatum

Methylene blue (MB) is a thiazine dye with cationic and lipophilic properties that acts as an electron transfer mediator in the mitochondria. Due to this metabolic improving activity and free radicals scavenging effects, MB has been used in the treatment of methemoglobinemia and ifosfamide-induced encephalopathy. Considering that methylmalonic acidemia consists of a group of inherited metabolic disorders biochemically characterized by impaired mitochondrial oxidative metabolism and reactive species production, we decided to investigate whether MB, protects against the behavioral and neurochemical alterations elicited by the intrastriatal injection of methylmalonate (MMA). In the present study we showed that intrastriatal injection of MB (0.015-1.5nmol/0.5microl) protected against seizures (evidenced by electrographic recording), protein carbonylation and Na(+),K(+)-ATPase inhibition ex vivo induced by MMA (4.5micromol/1.5microl). Furthermore, we investigated whether convulsions elicited by intrastriatal MMA administration are accompanied by striatal protein carbonyl content increase and changes in Na(+),K(+)-ATPase activity in rat striatum. The effect of MB (0.015-1.5nmol/0.5microl) and MMA (4.5micromol/0.5microl) on striatal NO(x) (NO(2) plus NO(3)) content was also evaluated. Statistical analysis revealed that the MMA-induced NO(x) content increase was attenuated by intrastriatal injection of MB and the duration of convulsive episodes correlated with Na(+),K(+)-ATPase inhibition, but not with MMA-induced total protein carbonylation. In view of that MB decreases MMA-induced neurotoxicity assessed by behavioral and neurochemical parameters, the authors suggest that MB may be of value to attenuate neurological deficits of methylmalonic acidemic patients.     

Monovalent cation activation in Escherichia coli inosine 5'-monophosphate dehydrogenase

Inosine 5'-monophosphate dehydrogenase (IMPDH) catalyzes the oxidation of inosine 5'-monophosphate (IMP) to xanthosine 5'-monophosphate with the concomitant reduction of NAD to NADH. Escherichia coli IMPDH is activated by K(+), Rb(+), NH(+)(4), and Cs(+). K(+) activation is inhibited by Li(+), Na(+), Ca(2+), and Mg(2+). This inhibition is competitive versus K(+) at high K(+) concentrations, noncompetitive versus IMP, and competitive versus NAD. Thus monovalent cation activation is linked to the NAD site. K(+) increases the rate constant for the pre-steady-state burst of NADH production, possibly by increasing the affinity of NAD. Three mutant IMPDHs have been identified which increase the value of K(m) for K(+): Asp13Ala, Asp50Ala, and Glu469Ala. In contrast to wild type, both Asp13Ala and Glu469Ala are activated by all cations tested. Thus these mutations eliminate cation selectivity. Both Asp13 and Glu469 appear to interact with the K(+) binding site identified in Chinese hamster IMPDH. Like wild-type IMPDH, K(+) activation of Asp50Ala is inhibited by Li(+), Na(+), Ca(2+), and Mg(2+). However, this inhibition is noncompetitive with respect to K(+) and competitive with respect to both IMP and NAD. Asp50 interacts with residues that form a rigid wall in the IMP site; disruption of this wall would be expected to decrease IMP binding, and the defect could propagate to the proposed K(+) site. Alternatively, this mutation could uncover a second monovalent cation binding site.     

Osmo and ionic regulation of black tiger prawn (Penaeus monodon Fabricius 1798) juveniles exposed to K(+) deficient inland saline water at different salinities

An 11-day trial was conducted to investigate the osmoregulatory capacity (OC) and regulation of K(+), Na(+), Ca(2+) and Mg(2+) of Penaeus monodon juveniles when exposed to K(+) deficient inland saline water (ISW) of four different salinities (5, 15, 25 and 35 ppt). The survival of juveniles showed a positive linear relationship (R(2) ranging from 0.72 to 0.98) with salinity. At the end of the trial, juveniles were able to survive only in 5 ppt of ISW and showed no changes in OC when transferred from ocean water (OW) to ISW. Further, the OC of juveniles in 5 ppt of ISW was significantly different (P<0.05) from the OC of juveniles exposed to 15, 25 and 35 ppt and exhibited strong serum K(+), Na(+), Ca(2+) and Mg(2+) regulation monitored over 16 h. In contrast, at 35 ppt, significant decrease (P<0.05) in serum K(+) and Mg(2+) concentrations and accumulation of serum Na(+) concentration occurred after 16 h of exposure to ISW. At higher salinity, an increase in serum Na(+) concentration leads to an increase in the serum osmolality of the juveniles, which in turn causes decrease in the OC of the juveniles. The results of this study suggest that K(+) deficiency in ISW has a negative effect on survival, OC and the ability of P. monodon juveniles to regulate serum Na(+), K(+), Ca(2+) and Mg(2+) concentrations. These effects are compounded as salinity increases.     

Activation of Na(+), K(+), Cl(-)-cotransport mediates intracellular Ca(2+) increase and apoptosis induced by Pinacidil in HepG2 human hepatoblastoma cells

The role of Na(+), K(+), Cl(-)-cotransport (NKCC) in apoptosis of HepG2 human hepatoblastoma cells was investigated. Pinacidil (Pin), an activator of ATP-sensitive K(+) (K(ATP)) channels, induced apoptosis in a dose- and time-dependent manner in HepG2 cells. Pin increased intracellular K(+) concentration ([K(+)](i)). Bumetanide and furosemide, NKCC inhibitors, significantly inhibited the Pin-induced increased [K(+)](i) and apoptosis, whereas K(ATP) inhibitors (glibenclamide and tolbutamide) had no effects. The Pin-induced [K(+)](i) increase was significantly prevented by reducing extracellular Cl(-) concentration, and Pin also increased intracellular Na(+) concentration ([Na(+)](i)), further indicating that these effects of Pin may be due to NKCC activation. In addition, Pin induced a rapid and sustained increase in intracellular Ca(2+) concentration ([Ca(2+)](i)), which was completely prevented by the NKCC inhibitors. Treatment with EGTA or BAPTA/AM markedly inhibited the Pin-induced apoptosis. Inhibitors of Na(+), Ca(2+)-exchanger, bepridil, and benzamil significantly prevented both [Ca(2+)](i) increase and apoptosis induced by Pin. Taken together, these results suggest that Pin increases [Na(+)](i) through NKCC activation, which leads to stimulation of reverse-mode of Na(+), Ca(2+) exchanger, resulting in [Ca(2+)](i) increase, and in turn, apoptosis. These results further suggest that NKCC may be a good target for induction of apoptosis in human hepatoma cells.     

Gill Na(+), K(+)-ATPase in a series of hyper-regulating gammarid amphipods: enzyme characterisation and the effects of salinity acclimation

The enzyme Na(+), K(+)-ATPase was investigated in the gills of selected hyper-regulating gammarid amphipods. Gill Na(+), K(+)-ATPase was characterised with respect to the main cation and co-factor concentrations for the freshwater amphipod Gammarus pulex. The optimum cation and co-factor concentrations for maximal gill Na(+), K(+)-ATPase activity in G. pulex were 100mM Na(+), 15mM K(+), 15mM Mg(2+) and 5mM ATP, at pH 7.2. The effects of salinity acclimation on gill Na(+), K(+)-ATPase activity and haemolymph sodium concentrations was investigated in selected gammarid amphipods from different salinity environments. Maximal enzyme activity occurred in all gammarids when acclimated to the most dilute media. This maximal activity coincided with the largest sodium gradient between the haemolymph and the external media. As the haemolymph/medium sodium gradient decreased, a concomitant reduction in gill Na(+), K(+)-ATPase activity occurred. This implicates the involvement of gill Na(+), K(+)-ATPase in the active uptake of sodium from dilute media in hyper-regulating gammarids.     

Electron microscopy of phospholipid vesicles reconstituted with purified renal Na,K-ATPase

Purified Na,K-ATPase after reconstitution into phospholipid vesicles catalyzed an active coupled transport with a ratio close to 3Na/2K. A uniform population of closed vesicles with average diameters close to 900 A are observed after freeze-fracture and thin sectioning. After freeze-fracture intramembranous particles with diameters of 80-100 A are observed. The data suggest that these particles correspond to Na,K-ATPase molecules.     

Requirement for negatively charged dispersions of phospholipids for interaction with lipid-depleted adenosine triphosphatase.

The basis of the requirement for a net negative charge on phospholipid dispersions able to re-activate lipid-depleted (Na++K+)-dependent adenosine triphosphatase was studied. The origin and density of the charge in phospholipid dispersions were varied before interaction with the adenosine triphosphatase protein, and the charge density on restored phospholipid-adenosine triphosphatase complexes was changed after interaction. The results indicated that: (a) re-activation requires a lamellar arrangement of the lipid molecules with sufficient density of negative charge, but not necessarily negatively charged phospholipid molecules; (b) the net charge appears to be necessary for the correct interaction between the enzyme protein and the phospholipids, although the amount of phospholipid that binds to the protein is also a function of the nature of the acyl chains; (c) it is not possible on the basis of these findings and those in the literature to decide unequivocally if the charge is also required for the enzyme reaction itself. The possible relevance of the findings to the situation in vivo is discussed in terms of the charge being concerned only with lipid-protein interaction.     

X-ray diffraction and foam film investigations of PC head group interaction in water/ethanol mixtures

The influence of ethanol on single phospholipid monolayers at the water/air interface and in foam films has been investigated. Grazing incidence X-ray diffraction investigations (GIXD) of Langmuir monolayers from 1,2-distearoyl-phosphatidylcholine (DSPC) spread on water subphases with different amounts of ethanol were performed. The thickness and free specific energy of formation of foam films stabilized by 1,2-dimyristoyl-phosphatidylcholine (DMPC) at different concentrations of ethanol in the film forming dispersions were measured. The GIXD investigations show that the tilt angle of the alkyl chains in the PC lipid monolayer decreases with increasing concentration of ethanol caused by a decrease of the diameter of the head groups. With increasing ethanol content of the solution also the thickness of the aqueous core of PC lipid foam films decreases. We assume that ethanol causes a decreasing probability for the formation of hydrogen bonds of water molecules to the PC head groups. The distinct difference between the effects of ethanol on lipid bilayers as described in the literature and on monolayers and foam films found in this study is discussed. Whereas PC monolayers at the water/air interface become unstable above 25 vol.% ethanol, the PC foam films are stable up to 50 vol.% ethanol. This is related to the decrease of the surface excess energy per lipid molecule by the interaction between the two film surfaces.