Surface Pressure Of Monolayers Research Articles

Synergistic effects of a membrane protein (spectrin) and Ca 2+ on the Na + permeability of phospholipid vesicles

1. 1.|Spectrin increases the surface pressure of phosphatidylserine and phosphatidylcholine monolayers when injected below the surface, to a greater extent at acid pH than at neutral pH. This effect is largest for phosphatidylserine monolayers, when increases in surface pressure are seen even at high initial film pressures (30–45 dynes/cm). Albumin shows similar effects. 2. 2.|Sonicated phosphatidylserine vesicles show very low 22Na + diffusion rates of 0.05 %/h, equivalent to 9·10 −13 cm/sec. The addition of spectrin and albumin increases this rate several orders of magnitude, to 20 and 75 %/h, respectively, but only at acid pH values (3.5–4.5). Spectrin also increases the diffusion rate of phosphatidylcholine vesicles 20-fold at pH 3.5, but has no effect at pH 7.4. 3. 3.|Ca 2+ and protein exhibit a synergistic effect on the permeability of phosphatidylserine and mixed phosphatidylserine/phosphatidylcholine vesicles. In contrast to protein alone, the effect of calcium plus protein is seen at both neutral and acid pH. Ca 2+ does not increase the effect of spectrin on phosphatidylcholine vesicles nor does it alter the penetration of spectrin into phosphatidylserine monolayers. Neither spectrin nor spectrin plus calcium have any effect on positively charged stearyl amine/phosphatidylcholine vesicles at pH 7.4. 4. 4.|The results are interpreted as indicating that both electrostatic attractions between protein and lipid, and conformational changes in the protein mediate penetration of the protein into the phospholipid bilayer, resulting in the large permeability increases observed. The role of Ca 2+ in the interactions is discussed. It is suggested that the binding of protein to phospholipid vesicles could produce areas of high negative charge density. Ca 2+ binding would then be enhanced leading to perturbations of the bilayer structure and to large increases in permeability.

A radiotracer study on hydrolysis of methyl- 14c palmitate in insoluble monolayers

Surface pressure and radioactivity ( R) of insoluble monolayers of methyl- 14C palmitate have been determined simultaneously as functions of time after spreading and of apparent molecular area ( A) of the ester which was contained originally in the spreading solution. A large rate of decrease in A is accounted for by the processes involving evaporation of the ester and its hydrolysis, to which a small rate of decrease in R is due.

The penetration of serum albumin into phospholipid monolayers of different fatty acid chain length and interfacial charge.

1. The highest surface pressure of phosphatidylcholine monolayers allowing penetration of delipidated serum albumin decreased in the order dibehenoyl>distearoyl>dipalmitoyl=dimyristoyl. This pressure was not related to the area occupied or to the space available between the phospholipid molecules at the interface. 2. Penetration of albumin into yeast phosphatidylcholine monolayers was increased by adding a small percentage of long-chain anions (phosphatidic acid, dicetylphosphoric acid) to the film but only when the protein was below its isoelectric point (i.e. positively charged). 3. Stearylamine added to phosphatidylcholine monolayers had no effect on albumin penetration even when the protein was oppositely charged to that of the phospholipid/water interface. 4. The results are discussed in relation to the activation of certain phospholipases by anionic amphipathic substances.

Studies of the Nylon Monolayer. III. The Interaction between the Nylon Monolayer and Acid Dye

Abstract The interaction of the monolayers of the Nylons 6 and 8 with the acid dye Orange II was studied by measuring the surface pressure of the nylon monolayers with and without Orange II in the substrate water. No change in the surface tension with the time was observed for the aqueous solution of Orange II in the concentration and pH ranges studied. The interaction between the nylon monolayers (film B) and Orange II was examined by observing the change in the F-A curve of the nylon monolayer due to the addition of Orange II to the substrate and the spreading of the solution. The presence of dye in a spreading solution has little effect, while the pH’s of the both the spreading solution and the substrate exhibit a marked effect on F-A curves. The observed interaction is compared with the behavior of practical dyeing in bulk of the solution.

Surface Pressure Relaxation and Hysteresis in Stearic Acid Monolayers at the Air-Water Interface

Time-dependent changes in the surface pressure of stearic acid monolayers were examined using an automated Wilhelmy-type film balance. Different surface pressure-area isotherms were obtained for two different rates of compression. Pressure relaxation from preselected surface pressures was examined as a function of time. The results indicated two types of relaxation which, along with the compression rate effect, may be rationalized on the basis of changes in molecular orientation and redistribution, together with expulsion from the monolayer at areas below the limiting area per molecule. Marked hysteresis effects were also noted when stearic acid monolayers were subjected to compression expansion cycles. The effect of repeated cycling and the minimum area of compression on hysteresis were investigated. The onset and extent of hysteresis may also be explained on the basis of expulsion and reentry and orientation and redistribution of molecules at the interface.

Fatty acid monolayers in the expanded state: II. The effect of compression velocities

In order to make clear physicochemical states of monolayers, the effect of compression velocities on the monolayers of myristic and stearic acids was investigated. It was observed that the surface pressure vs. area (π vs. A) curves of the myristic acid monolayer were markedly affected by compression velocities, whereas those of the stearic acid monolayer were virtually the same for various compression velocities. The effect of compression velocities on the myristic acid monolayer was explained by its desorption; this was proved theoretically by a desorption mechanism by which the molecules dissolve into the underlying solution and then diffuse away from the surface. The π vs. A n curve, where A n is the net area per molecule, for myristic acid was satisfactorily described by the equation of state developed in Part I of this series.

Infrared Spectra and Surface Pressure of Myristic Acid Monolayers on Iron Chloride Solutions.

Infrared spectra and surface pressure of myristic acid monolayers on iron chloride solutions

The surface properties of pure phospholipids in relation to those of lung extracts

An investigation has been undertaken into the surface pressure and surface potential of thin films of certain pure and mixed phospholipids in relation to the surface properties exhibited by crude lung extracts. The high stable surface pressures obtained by compression of monolayers of saturated, choline-containing phospholipids, in contrast to the corresponding ethanolamine phospholipids, has been attributed to the uniquely close surface packing of the former molecules, which is possible almost throughout their entire length. Certain foreign molecules render such structures unstable, but others are eliminated by “squeeze-out” during compression. The “characteristic” surface properties of lung surfactant can be ascribed to various causes as follows. High surface pressure: to high dipalmitoyllecithin content with perhaps some contribution by other disaturated choline phospholipids and sphingomyelin; instability and gel-liquid state at high pressure : to heterogeneity of the compressed film; “hysteresis”: to replacement from a “surface store”, during expansion, of surfactant eliminated by “squeeze-out” during previous compression; plateau in the compression phase at about 45–50 dyne/cm : to rapid “squeeze-out” of some of the more readily eliminated substances, this “squeeze-out” then continuing at a slower rate throughout the remainder of the compression phase but remaining incomplete. In addition, it has been suggested that a conformational change of the choline moiety from a co-planar to a co-axial arrangement occurs during compression of saturated choline phospholipids and may contribute to the surface pressure and surface potential characteristics of monolayers of such substances and of lung extracts.

Interaction of polyene antibiotics with single and mixed lipid monomolecular layers

1. 1. Etruscomycin, amphotericin B, and pimaricin preferentially interact with cholesterol, and not with lecithin, monolayers at low molar ratios of antibiotic/lipid. Similar results have been previously reported for filipin and nystatin. At initial surface pressures above the collapse pressures of the antibiotics, the ability of the polyenes to increase the surface pressure of a cholesterol monolayer is in the order: filipin ⪢ etruscomycin ⪢ amphotericin B > pimaricin > nystatin. These observations suggest that the ability of the polyene antibiotics to cause membrane damage may be correlated with their affinity for sterol. Derivatives of filipin, which have little or no biological activity, also prduce a much weaker interaction with cholesterol monolayers than the parent antibiotic. 2. 2. In mixed monolayers of lecithin and cholesterol, the surface pressure increase obtained with filipin is diminished as the relative content of the phospholipid is raised. This observation supports previous studies indicating that the polyene sensitivity of a membrane may be dependent on the phospholipid/sterol ratio and not on the presence of sterol per se. 3. 3. Filipin, nystatin and pimaricin can interact with monolayers of lecithin (in the absence of cholesterol) at high molar ratios of antibiotic/lipid. These observations are consistent with the results of e sessa and W weissmann that some of the polyenes can release markers from liposomes prepared with lecithin alone. Past and present experiments suggest that interaction between the polyenes and membrane phospholipid is probably without significance as regards the antifungal and hemolytic activity of the antibiotics. At high molar ratios, filipin can also increase the surface pressure of oleic acid monolayers. These results are in accord with several reports indicating that addition of fatty acids, as well as phospholipids, to the medium can antagonize the growth inhibitory and lytic properties of the polyenes. 4. 4. Filipin has only a slight effect on the surface pressure of cholesterol acetate monolayers, which is consistent with the view that a free hydroxyl group is necessary for interaction with the polynees. This conclusion is supported by the fining that filipin can also interact with monolayers of cetyl alcohol at low molar ratios of antibiotic/lipid. The inhibitory influence of urea suggests that hydrogen bond formation may play an important role in polyene sterol—interaction.

Transport of ions across lipid monolayers: II. Reduction of polarographic currents of Cu(II) by decylammonium monolayers

The rate of transport of Cu (II) ions across a decylammonium monolayer was measured as a function of decylamine and salt concentration and also of potential using the polarographic technique. Utilizing information about the structure of the monolayer, it is possible to give the transport results in terms of molecular parameters. For constant salt concentration, the monolayer permeability to ions decreases with an increase in monolayer concentration and surface pressure. The effects of varying salt concentration on the permeability are somewhat complicated because of simultaneous changes in surface concentration and pressure. Some unusual humps in the polarogram appear to be due to the adsorption of micelles above the critical micelle concentration. The data were analyzed in terms of transport rate constants for crossing the monolayer on the basis of a model due to Koutecky. An expression for the rate constant was derived in terms of absolute rate theory and an activation area was estimated on this basis. The derived rate constant helps to explain a number of aspects of the transport process including the conclusion that the transported ionic species is actually monovalent.

Apparent dipole moment of a long-chain surfactant molecule in a gaseous monolayer from surface potential measurements

The Helmholtz model of the simple parallel-plate condenser has often been used to represent the potential across the double layer resulting from spreading a long-chain surfactant at the air/water interface. Guastalla, using a modified Helmholtz model, has suggested a method for determing the apparent dipole moment of the surfactant molecule in the gaseous region. The method involves extrapolation of experimental surface potential and surface concentration data to infinite dilution of surfactant. Surface potentials and surface pressures of gaseous monolayers of myristic and palmitic acids over aqueous substrates at various pit have been investigated. The apparent dipole moment and molecular weight of the spread molecule have been calculated from these data. When the pit of the aqueous substrate is below 4.5, the fatty acid is molecularly dispersed and the low surface potential indicates that the apparent dipole moment of the fatty acid is small; either the fatty acid molecule lies practically flat on the surface of the liquid or interaction between the long-chain fatty acid and the water molecules of the substrate occurs. When the pH of the aqueous substrate is above 4.5, the fatty acid gradually ionizes and the monolayer slowly desorbs. It is concluded that the Guastalla interpretation of the dipole moment is inadequate.

Lipid-protein in teraction at the air-water interface

1. 1.The spreading of a protein solution with a glass rod into the plane of a cholesterol monolayer greatly reduced the time necessary to attain an equilibrium surface pressure in the mixed monolayer. The results obtained with this spreading method coincided with those obtained by injecting the protein solution into the bulk of the subphase supporting the lipid monolayer. 2. 2.On a phosphate buffer solution (pH 7.2) there was a linear relationship between the total surface pressure of the mixed monolayer and the molar fraction of amino acid residues at the air-water interface; this suggests a non-specific dissolution process in which the hydrocarbon chains of the amino acid residues and the cholesterol molecules are the chemical species involved. 3. 3.The free energy of mixing for this process, as well as for the surface dissolution of cetyl alcohol and cholesterol, practically coincided with that corresponding to an ideal system; this suggests that the driving forces for both processes could be of entropic origin and that no specific interactions occur between the components of the surface solution.

Phase Transitions in Poly-n-Alkyl Methacrylate Monolayers

Abstract The effects of temperature on the surface pressure of monolayers of polymethacrylates with n-alkyl groups containing from 9 to 18 carbon atoms have been studied. Two kinds of phase transitions have been observed in the surface pressure-area isotherms. On the basis of the bulk properties of the polymers, these phase changes have been interpreted as the transition of the monolayer to a three-dimensional fluid state and as side-chain crystallization.

Studies on membrane model. I. Surface pressure and surface potential of pure phospholipid monolayers.

Studies on membrane model. I. Surface pressure and surface potential of pure phospholipid monolayers.

The interaction of the psychotomimetic glycolate esters with adenosine triphosphate, calcium and lecithin monolayers

The action of a psychotomimetic agent, N-methyl-3-piperidinol cyclopentyl-phenylglycolate on the surface pressure and surface viscosity of lecithin monolayers was investigated. Evidence is presented suggesting that PMCG is associating with the phosphate group of the lecithin as well as with the fatty acid chains of the lecithin molecule. Also, it was shown that the drug forms associations with Ca 2+ and phosphate ions and with ATP. The association with ATP primarily involves the adenine group, while the phosphate chain interferes in some manner with this association. The results are discussed in terms of their possible significance in explaining some of the observed effects of PMCG and related agents on excitable tissue.

Influence of Water Structures on the Surface Pressure, Surface Potential, and Area of Soap Monolayers of Lithium, Sodium, Potassium, and Calcium

Influence of Water Structures on the Surface Pressure, Surface Potential, and Area of Soap Monolayers of Lithium, Sodium, Potassium, and Calcium

The action of calcium and anticholinergic psychotomimetic agents on surface films

The action of a psychotomimetic agent, N-methyl-3-piperidyl glycolate (NPB), was investigated on the surface pressure and surface viscosity of interfacial monolayers of stearic acid. A comparison was made between the action of calcium and NPB on the physicochemical properties of surface films. Both calcium and NPB interact with the film to promote condensation and increase surface viscosity. There is a close similarity in the pressure-area curves and the viscosity changes obtained with both calcium and NPB that suggests a similarity in their mode of interaction with the film. It is proposed that NPB can interact with two adjacent stearic acid molecules by virtue of electrostatic, hydrogen bond, and van der Waals forces. NPB can also interact with surface films in a manner which is different from calcium, and so impart additional effects to the film. The findings are discussed in terms of their possible significance to an understanding of the role of calcium in the bioelectric membrane.

Properties of ionized monolayers. Part 5.—Surface potentials and pressures of insoluble monolayers of sodium octadecyl sulphate

Properties of ionized monolayers. Part 5.—Surface potentials and pressures of insoluble monolayers of sodium octadecyl sulphate

The interaction of myristic acid monolayers with thorium and lanthanum solutions

The hydrolysis of thorium and lanthanum ions in solution, although of general chemical interest, is of particular importance in colloid chemistry in view of the importance of these ions in studies on the flocculation of lyophobic colloids. Unfortunately conventional electrometric methods of investigating hydrolysis require a high concentration of hydrolyzable cation and an even higher concentration (ca. 3 M) of added “inert” electrolyte; the method is not sufficiently sensitive to detect hydrolysis in the concentration regions of interest to colloid chemistry. However, the transition surface pressure of myristic acid monolayers forms a very sensitive detector of ion hydrolysis in the lower pH regions. Moreover, hydrolysis can be detected in solutions as dilute as 10 −6 M in the absence of added electrolyte. In this paper the interaction of myristic acid monolayers with thorium and lanthanum is used as a method of investigating the hydrolysis of these ions.

Surface viscosities of mixed unimolecular films

Variations of the surface viscosities with surface pressure of binary mixed monolayers of stearic acid with octadecanol and with arachidic acid were measured. A torsional surface viscometer was employed together with a horizontal-type film balance and a surface trough which was maintained at 25.00°C. The observed fluidities indicated that homogeneous surface solutions were formed throughout the entire composition ranges of both mixtures. The long-chain fatty acid mixtures appeared to give nearly perfect monolayer solutions, whereas complex intermolecular interactions occurred in the acid + alcohol solutions.