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PubMed1988

Insulin-induced changes in mechanical characteristics of lipid bilayers modified by liver plasma membrane fragments.

Insulin interaction with BLM with incorporated fragments of rat liver plasma membranes, containing hormone receptors, was studied by determining Young modulus of elasticity of bilayer lipid membranes in direction perpendicular to the surface, E. The presence of membrane proteins in a concentration of 60 micrograms.ml-1 induced a significant decrease in parameter E (to approx. 50%) as compared with values obtained in non-modified membranes during insulin action (concentration interval 10(-11)-10(-9) mol.l-1). The extent of the effect was dependent on the initial phase state of the membrane, on cholesterol content in BLM as well as on membrane proteins concentration in lipid bilayer.

Animals↗
PubMedDate not supplied

[Effect of chromium (III) ions and a cysteine complex of it on lipid bilayer membranes].

The interaction of Cr3+ ions and its cysteine complex with bilayer phospholipid membranes was investigated. It was found that chromium ions and the complex compound are adsorbed on the bilayer lipid membrane surface, changing the intramembrane potential difference. As pH increases, the adsorption of Cr3+ decreases and that of the complex rises. The adsorption of the complex leads to an increase in the rigidity of bilayer lipid membrane, which is not observed with chromium ions.

Chromium↗
PubMed1980

The appearance of single-ion channels in unmodified lipid bilayer membranes at the phase transition temperature.

Ion-specific channels in artificial membranes have been formed by the addition of gramicidin A, alamethicin, polyene antibiotics and some proteins to the solution surrounding the bilayer lipid membrane. Until now there have been no reports of single-ion channels in unmodified lipid membranes. We have now studied the electrical conductance of planar lipid bilayers membranes made of synthetic distearoylphosphorylcholine (DSPC). Current fluctuations of amplitude approximately 1pA and duration approximately 1 s have been discovered at phase transition temperature, which shows that the appearance of ionic channels may be the result of lipid domain interactions. This would explain the dramatic increase in ion permeability observed in liposomes during phase transition. We suggest that these channels could conduct the transmembrane ionic current in biological membranes without the involvement of peptides and proteins.

Electric Conductivity↗
PubMed1990

Rimantadine effects on the elasticity of bilayer lipid membranes and on ion transport through gramicidin D channels.

The effect of the antiviral preparation rimantadine on lipid bilayer membranes (BLM) was studied by measuring the modulus of elasticity in the direction normal to the surface (E perpendicular) and by estimating the conductance lambda, the lifetime tau of single gramicidin D channels (GRD), and the coefficient of nonlinearity beta of current voltage characteristics (IVC) of GRD-modified BLM. Rimantadine induced a nonmonotonic change in E perpendicular of BLM prepared from a mixture of egg lecithin with cholesterol: at relatively low rimantadine concentrations (0-40 micrograms/ml) E perpendicular first increased, reached a maximum and started to decrease. The effectivity of rimantadine was dependent on the cholesterol concentration in the BLM. Changes in E perpendicular suggest an increased ordering of the lipid bilayer at low rimantadine concentrations and formation of clusters of the preparation at concentrations exceeding those necessary to obtain maximal values of E perpendicular for the given BLM lipid composition. Rimantadine concentrations lifetime by approximately 20 percent, affected the degree of IVC nonlinearity and superlinearity of GRD-modified membranes, which suggests some effect on the height of the barrier at the ionic channel mouth and in its centre.

Cholesterol↗
PubMed2006

Tethered lipid bilayers on electrolessly deposited gold for bioelectronic applications.

This paper presents the formation of a novel biomimetic interface consisting of an electrolessly deposited gold film overlaid with a tethered bilayer lipid membrane (tBLM). Self-assembly of colloidal gold particles was used to create an electrolessly deposited gold film on a glass slide. The properties of the film were characterized using field-effect scanning electron microscopy, energy dispersive spectroscopy, and atomic force microscopy. Bilayer lipid membranes were then tethered to the gold film by first depositing an inner molecular leaflet using a mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphoethanolamine-N-[3-(2-pyridyldithio)propionate], 1,2-di-O-phytanyl-sn-glycero-3-phosphoethanolamine (DPGP), and cystamine in ethanol onto a freshly prepared electrolessly deposited gold surface. The outer leaflet was then formed by the fusion of liposomes made from DPGP or 1,2-dioleoyl-sn-glycero-3-phosphocholine on the inner leaflet. To provide functionality, two membrane biomolecules were also incorporated into the tBLMs: the ionophore valinomycin and a segment of neuropathy target esterase containing the esterase domain. Electrochemical impedance spectroscopy, UV/visible spectroscopy, and fluorescence recovery after pattern photobleaching were used to characterize the resulting biomimetic interfaces and confirm the biomolecule activity of the membrane. Microcontact printing was used to form arrays of electrolessly deposited gold patterns on glass slides. Subsequent deposition of lipids yielded arrays of tBLMs. This approach can be extended to form functional biomimetic interfaces on a wide range of inexpensive materials, including plastics. Potential applications include high-throughput screening of drugs and chemicals that interact with cell membranes and for probing, and possibly controlling, interactions between living cells and synthetic membranes. In addition, the gold electrode provides the possibility of electrochemical applications, including biocatalysis, bio-fuel cells, and biosensors.

Colloids↗
PubMed1990

Calmodulin interaction with mesocaine-modified lipid bilayer.

Calmodulin (CaM) interactions with bilayer lipid membranes (BLM) were studied by measuring modulus of elasticity in direction perpendicular to the membrane plane (E perpendicular) and intramembrane potential delta psi. Upon interaction of CaM with egg phosphatidylcholine and asolectin BLM the parameter E perpendicular grew slightly (not more than by 10% as compared to the respective vale for nonmodified BLM), suggesting a weak effect on the ordering of the hydrophobic moiety of the lipid bilayer. In the presence of mesocaine (Mes), a calmodulin inhibitor, CaM affected the incorporation of Mes into the membrane. It can be concluded that CaM affects the ordering of the polar (superficial) membrane region.

Acetanilides↗
PubMed2004

The protein-tethered lipid bilayer: a novel mimic of the biological membrane.

A new concept of solid-supported tethered bilayer lipid membrane (tBLM) for the functional incorporation of membrane proteins is introduced. The incorporated protein itself acts as the tethering molecule resulting in a versatile system in which the protein determines the characteristics of the submembraneous space. This architecture is achieved through a metal chelating surface, to which histidine-tagged (His-tagged) membrane proteins are able to bind in a reversible manner. The tethered bilayer lipid membrane is generated by substitution of protein-bound detergent molecules with lipids using in-situ dialysis or adsorption. The system is characterized by surface plasmon resonance, quartz crystal microbalance, and electrochemical impedance spectroscopy. His-tagged cytochrome c oxidase (CcO) is used as a model protein in this study. However, the new system should be applicable to all recombinant membrane proteins bearing a terminal His-tag. In particular, combination of surface immobilization and membrane reconstitution opens new prospects for the investigation of functional membrane proteins by various surface-sensitive techniques under a defined electric field.

Biomimetics↗
PubMedDate not supplied

[Effect of human plasma lipoproteins on ionic conductivity of lipid bilayer membranes].

An interaction was studied between various lipoproteins (low density lipoproteins--LDL, very low density lipoproteins--LVDL, subfractions of high density lipoproteins--HDL2, HDL3) and artificial bilayer lipid membranes (BLM) produced from oxydized cholesterol. The lipoproteins increased from 100 to 1000-fold the conductivity of BLM for cations Na+, K+, Ca2+, but not for anions. Critical concentrations of the lipoproteins at which their modifying effect was manifested, correlated reciprocally with the size of the lipoprotein particles; they were arranged as follows: VLDL < LDL < HDL2 < HDL3. Decrease in the pH value lowered these critical concentrations. Addition of Ca2+ into the solution decreased the critical concentrations of VLDL and LDL from 2- to 4-fold as well as of HDL2 and HDL3--from 9- to 12-fold. The electrostatic power appears to be important in interaction between the lipoproteins and bilayer lipid membranes.

Adult↗
PubMed1989

[Effect of beta-lactam antibiotics on lipid bilayer membranes. I. Penicillin antibiotics].

Interaction between penicillins and model membrane systems, flat black bilayer lipid membranes (BLM) composed of vegetable or bacterial phospholipids was studied with an account of the complicated structure of bacterial cell membranes and possible presence in them of "pure" bilayer lipid areas. By their effect on electroconductivity of the BLM the antibiotics could be divided into three groups: those having no effect on the BLM electroconductivity at the maximum concentrations i.e. benzylpenicillin, carbenicillin, piperacillin (at pH 6.0 and 7.0) and ampicillin (at pH 6.0), those insignificantly changing electroconductivity of the BLM i.e. carfecillin and azlocillin and those having a significant effect on the BLM electroconductivity i.e. ampicillin N-acyl derivatives and 6-APA. The effect of ampicillin on the BLM conductivity markedly depended on the electrolite pH. The penicillins bound to the bilayer and induced changes in the transmembrane potential (evident from the changes in the second harmonic of the capacitive current) and the BLM elasticity-capacitance parameters (evident from the changes in the ratio of the amplitudes of the first and third harmonics). It was shown that all the penicillins penetrated through the BLM composed of either vegetable or bacterial phospholipids. The capacity for the transmembrane transfer without changing of the bilayer conductivity must be connected with the fact that the penetrating antibiotics did not induce any changes in the BLM structure. The effect on the conductivity probably depended in its turn on the form of the molecule and the ratio of the hydrophilic and hydrophobic parts in it.

Electrolytes↗
PubMed1986

Phospholipid surface bilayers at the air-water interface. III. Relation between surface bilayer formation and lipid bilayer assembly in cell membranes.

Lipid bilayer assembly in cell membranes has been simulated with total lipid extracts from human red blood cells and from mesophilic and thermophilic bacteria grown at several temperatures. Aqueous dispersions of these natural lipid mixtures form surface bilayers, a single bimolecular lipid state, but only at the growth temperature of the source organism. Thus, a single isolated bilayer state forms spontaneously in vitro from lipids that are available in vivo at the growth temperature of the cell. Surface bilayers form at a specific temperature that is a function of hydrocarbon chain length and degree of fatty acid unsaturation of the phospholipids; this property is proposed as an essential element in the control of membrane lipid composition.

Air↗
PubMed1999

An analysis of the size selectivity of solute partitioning, diffusion, and permeation across lipid bilayers.

The lipid bilayers of cell membranes are primarily responsible for the low passive transport of nonelectrolytes across cell membranes, and for the pronounced size selectivity of such transport. The size selectivity of bilayer permeation has been hypothesized to originate from the hindered transport of solutes across the ordered-chain region. In this paper, we develop a theoretical description that provides analytical relationships between the permeation properties of the ordered-chain region of the lipid bilayer (partition and diffusion coefficients) and its structural properties, namely, lipid chain density, free area, and order parameter. Emphasis is placed on calculating the size selectivity of solute partitioning, diffusion, and overall permeability across the ordered-chain region of the lipid bilayer. The size selectivity of solute partitioning is evaluated using scaled-particle theory, which calculates the reversible work required to create a cavity to incorporate a spherical solute into the ordered-chain region of the lipid bilayer. Scaled-particle theory is also used to calculate the work required to create a diffusion path for solutes in the interfacial region of the lipid bilayer. The predicted size dependence of the bilayer permeability is comparable to that observed experimentally. The dependence of solute partition and diffusion coefficients on the bilayer structural parameters is also discussed.

Diffusion↗
PubMed1990

Structure of polymerizable lipid bilayers: water profile of a diacetylenic lipid bilayer using elastic neutron scattering.

Elastic neutron scattering experiments have been used to study the hydration of multibilayers of 1,2-bis(10,12-tricosadiynoyl)-sn-glycero-3-phosphocholine (DC8,9PC). Previously published FTIR spectroscopic data had suggested, based on shifts in the carbonyl (C = O) stretch frequencies, that the phosphocholine headgroup in these polymerizable lipid bilayers was much less hydrated than that of saturated phosphatidylcholines. Our results demonstrate that the DC8,9PC headgroup is at least as well hydrated as that of dipalmitoylphosphatidylcholine (DPPC), a saturated lipid, under the same conditions.

1,2-Dipalmitoylphosphatidylcholine↗
PubMed1989

Conductance transition induced by an electric field in lipid bilayers.

A cooperative phenomenon showing a structural change in the organization of bilayer lipid membranes at a critical value of the applied electric field is presented. The transition is characterized by a sharp increase in conductance. The phenomenon can be observed under current-clamp conditions (rather than the usual voltage-clamp conditions) to avoid rupturing the membrane. At a critical potential value the conductance increases and therefore the potential decreases to keep the current constant. Results refer to membranes made of egg phosphatidylcholine (PC), diphytanoylphosphatidylcholine and cholesterol/egg PC. It is found that the critical potential at which the transition occurs depends dramatically on pH and ionic concentration, indicating that the electrical properties of the external surface determine the major characteristics of such a transition.

Cholesterol↗
PubMed1990

Detection of transient capacitance increase associated with channel formation in lipid bilayers.

The insertion of alpha- and beta-latrotoxins and sea anemone (Radianthus macrodactilus) toxin into bilayer lipid membranes (BLMs) was investigated using the method of simultaneous conductance/capacitance measurement. All the toxins investigated induced capacitance changes which preceded toxin-induced conductance increases. The processes that may underlie the observed effect are discussed.

Animals↗
PubMed1990

Effects of local anesthetics on mechanical characteristics of lipid bilayers and on the ion transport dynamics.

Bilayer lipid membranes (BLM) of various composition were used to study the effects of local anesthetics (LA) carbisocaine and lidocaine on mechanical membrane characteristics and on the transport dynamics of ions across gramicidin D ionic channels. Carbisocaine concentrations of 20 mumols/l-0.1 mmol/l caused a considerable decrease (by 15-40%) in modulus of elasticity E1 in direction perpendicular to membrane surface. The effect of lidocaine was approx. one order of magnitude weaker. LA-induced changes in E1 were shown to depend on both the lipid composition of the membrane and the electrolyte pH. Neutral forms of LA induce marked changes in E1. An analysis of current-voltage (I-V) characteristics of BLM modified by the channel forming agent gramicidin D revealed that carbisocaine significantly affects the superlinear segment of the I-V relationship; this suggests a strong effect on the transport dynamics of ions through the internal channel region. The results of the study suggest that the action of both carbisocaine and lidocaine may be non-specific. The effectivity of the non-specific action of LA is determined by the hydrophobic moiety of the local anesthetic molecule.

Anesthetics, Local↗
PubMed1990

[Modeling of damage to cell membranes during photodynamic therapy: photosensitization of planar lipid bilayers by hematoporphyrin dimethyl ether].

The variations of electrical conductance of planar bilayer lipid membranes (BLM) sensitized by hematoporphyrin dimethyl ether under visible light illumination were studied. The conductance of BLM does not change for some period after switching on the light, then an increase in the conductance starts and the membrane breaks. This "induction" time does not depend on addition of azide or ferricyanide to the solution, on addition of BHT to the lipid and on substitution of air for argon in the cell. The induction time for any new BLM, formed in the same cell immediately after the previous membrane was broken, is shorter. The variation of BLM boundary potentials during induction time was not observed. The results obtained suggest that the photodamage of BLM sensitized by HPD leads to accumulation of uncharged reaction products and oxygen does not take part in this process.

Cell Membrane↗
PubMedDate not supplied

[Properties of lipid bilayer membranes modified by brain Na+,K+-ATPase subunits].

Large (alpha) and small (beta) subunits (SU) of the enzyme were obtained from the high-purified Na+, K+-ATPase preparations of the cattle brain. Molecular masses of the subunits (95 and 55 kD, respectively) have been determined and the properties of bilayer lipid membranes (BLM) modified by them were investigated. The both proteins are capable of inducing the channel conductivity in BLM which is selective to alkaline metals ions in case of alpha-SU, alpha-SUE modified BLM possess some properties of Na+, K+-ATPase: the cardial glucosides at large and small doses have a specific action, the action of the above glycosides and vanadate differs; vanadate intensifies the inhibitory effect of ouabain; the cardial glycosides and K+ have an antagonistic action; the effect of ouabain depends on the content of Ca2+ in the medium. At the same time other properties of this enzyme (dependence on ATP, magnesium ions, etc.) are not manifested with introduction into BLM. It is supposed that the ability of Na+, K+- ATPase subunits to form channel-like current fluctuations in BLM is a property of the obtained proteins and it is not obligatory realized in the processes of active K+ and Na+ transmembrane transfer.

Animals↗
PubMed2001

Optimization of receptor-G protein coupling by bilayer lipid composition II: formation of metarhodopsin II-transducin complex.

The visual transduction system was used as a model to investigate the effects of membrane lipid composition on receptor-G protein coupling. Rhodopsin was reconstituted into large, unilamellar phospholipid vesicles with varying acyl chain unsaturation, with and without cholesterol. The association constant (K(a)) for metarhodopsin II (MII) and transducin (G(t)) binding was determined by monitoring MII-G(t) complex formation spectrophotometrically. At 20 degrees C, in pH 7.5 isotonic buffer, the strongest MII-G(t) binding was observed in 1-stearoyl-2-docosahexaenoyl-sn-glycero-3-phosphocholine (18:0,22:6PC), whereas the weakest binding was in 1-stearoyl-2-oleoyl-sn-glycero-3-phosphocholine (18:0,18:1PC) with 30 mol% cholesterol. Increasing acyl chain unsaturation from 18:0,18:1PC to 18:0,22:6PC resulted in a 3-fold increase in K(a). The inclusion of 30 mol% cholesterol in the membrane reduced K(a) in both 18:0,22:6PC and 18:0,18:1PC. These findings demonstrate that membrane compositions can alter the signaling cascade by changing protein-protein interactions occurring predominantly in the hydrophilic region of the proteins, external to the lipid bilayer. These findings, if extended to other members of the superfamily of G protein-coupled receptors, suggest that a loss in efficiency of receptor-G protein binding is a contributing factor to the loss of cognitive skills, odor and spatial discrimination, and visual function associated with n-3 fatty acid deficiency.

Cholesterol↗