Equilibrium and metastable states in lecithin films

Horn, L.W.; Gershfeld, Norman L.

doi:10.1016/s0006-3495(77)85615-4

Cited by 71 publications

(16 citation statements)

References 20 publications

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“…By contrast, DPPC exhibits negligible surface tension lowering when it is placed on a water surface in powdered crystal form below T,, as found by Villalonga (21) and Phillips and Hauser (15), and as verified here in Table 1, case 2. The adsorption of DPPC is thus path dependent, and this correlates with the concept that, from a thermodynamic viewpoint, phosphatidylcholines below T, can exist in metastable onequilibrium states (4,6,15).…”

Section: Resultsmentioning

confidence: 65%

Path Dependence of Adsorption Behavior of Mixtures Containing Dipalmitoyl Phosphatidylcholine

et al. 1982

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Summaryor vortexing of a phospholipid mixture of a specific chemical composition may result in an aqueous dispersion of varying he adsorption of aqueous phospholipid dispersions containing composition due to differences in the ease of dispersion of mixture dipalmitoyl phosphatidylcholine (DPPC) is investigated at 35-components. Consequently, a clear probability exists for the for-370C as a preparation technique. Systems mation of variable bulk solution states in lung surfactant replacestudied in terms of surface pressure-time (74) adsorption behavior ment mixtures containing a high % of p~o s p~o~~p~~s~ T-~~~ difwere pure DPPC, 9:1 DPPC:di~almito~l ~~o s~h a~~~~~~t~a~~~~-ferent solution states can exhibit significant surface property difmine, I3 DPPC:egg P~~~P~~~~~Y~~~Y~~~~ (PG), and lipids ex-ferences. This raises the possibility that the therapeutic efficacy of from ' Ow lung lavage. The show that T -~ charac-a specific surfactant replacement mixture will not only be dependteristics can differ significantly depending on the technique by ent upon mixture compos~t~on, concentration, and delivery which the DPPC-containing mixtures are initially dispersed in method (which are currently receiving considerable attention), but 0.15 M NaCl solution. Examples of path dependence include the also upon the solution preparation procedure.fact that DPPC, which will not adsorb at T = 3S0C when placed one surface property that may depend strongly on dispersion in powdered crystals on the subphase surface, exhibits measurable is adsorption.a first step to characterizing the *rr-t changes after subphase dispersion by sonication or by mechan-potential magnitude of such effects on lung surfactant replaceical vortexing. For I 3 DPPC:PG, dispersion by sonication on ice ment, we investigated the adsorption of phospholipid mixtures or by mechanical vortexing gives faster adsorption than dispersion dipahitoyl p~o s p~a t i~y~c~o~~e (DPPC) for a variety by sonication without temperature control. The effect of heating of initial conditions. l-he solution preparation method was the to T = 4s0c, which is greater than the gel to liquid crystal variable in all cases investigated, with subphase ionic composition, temperature of DPPC ( T~ = 410C)9 is found be total surfactant concentration, and subphase temperature held particularly detrimental to the adsorptionof 7:3DPPC:PG. Of the E~~~-~~~ were done for pure DPPC and for the phospholipid mixtures studied, extracted cow lung lipids exhibited mixed systems of 7:3 (molar ratio) D P P C~ by far the greatest adsorption capability and also showed less path (PG) and 9: 1 ~~~~: d i~~l m i t~~l phosphatidylethanolam~ne dependence than I 3 DPPCPG. Similarly, in terms of dispersion (~p p~) , addition, adsorption were on techniques investigated, sonication on ice tended to give the most mixed lipids extracted by chlorofom and methanol from calf lung rapid adsorption for a given phospholipid mixture. lavage. The results support the interpretation that DPPC adsorption from aqueous dispersion differs depe...

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Section: Resultsmentioning

confidence: 65%

Path Dependence of Adsorption Behavior of Mixtures Containing Dipalmitoyl Phosphatidylcholine

et al. 1982

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“…As already reported [Ill, stepwise addition of lipids gave compression curves which are somewhat more expanded than the ones obtained by a continuous compression (moving barrier system). Such differences, originating in the way the films are formed have recently been discussed [30]. Nevertheless it is thought that the diffusion transition has only to be connected to the appearance of a well defined gel state.…”

Section: Discussionmentioning

confidence: 99%

A Fluorescence Approach of the Determination of Translational Diffusion Coefficients of Lipids in Phospholipid Monolayer at the Air-Water Interface

Teissié¹,

Tocanne²,

Baudras³

1978

Eur J Biochem

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In the present work, it is shown that the photobleaching technique as well as experimentation based on fluorescence recovery after bleaching can be extended to monolayers spread at the air-water interface. A mathematical model is derived which allows the determination of translational diffusion coefficients of species diffusing in such a system. Using 12-(9-anthroyl)stearic acid (anthroylstearate) as a fluorescent probe, dispersed either in dipalmitoylphosphatidylcholine or in dipalmitoylphosphatidylglycerol in various conditions of subphase ionic composition and surface pressure of the monolayer, including phase transition domains, we are led to the following conclusions :1. Anthroylstearate molecules seem to aggregate in 'microdomains' where their fluorescence properties remain unchanged regardless of the compression states of the host monolayer.2. In any case, a break in the diffusion constants appears on compressing films of both dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylglycerol. In particular, this break coincides with the liquid expanded to gel phase transition of these lipids when it occurs.3. Diffusion of anthroylstearate in dipalmitoylphosphatidylglycerol depends strongly on the subphase ionic strength and on the nature of cations: Na', Mg2+, Ca2+.In recent years, much interest has been expressed in the study of lateral diffusion of phospholipids and proteins in biomembranes. Such a process which participates in the more general concept of 'membrane fluidity' seems to play a significant role in modulating membrane functions of some proteins [l]. Many of the studies reported on lateral diffusion have been carried out by use of spectroscopic methods, basically electron spin resonance [2], nuclear magnetic resonance , whereas experimentation on monolayers have been scarce and based on the use of radioactive tracers [lo]. Lipid monolayers at the air-water interface have proved to be good membrane models in which not only the temperature and subphase pH and ionic composition can be controlled, but also the molecular packing of the lipids. We have reported recently [ 111 that fluorescence measurements are feasible with such monolayers at very low concentrations of the probe (mole ratio of the order of In the present work, the photobleaching technique has been extended to monolayers and the experimentation based on fluorescence recovery after bleaching as well. A mathematical treatment of the data has been derived which allows the determination of translational diffusion coefficients in such a system. The results presented deal with the diffusion of 12-(9-anthroy1)stearic acid (anthroylstearate) dispersed either in dipalmitoylphosphatidylcholine or in dipalmitoylphosphatidylglycerol in various conditions of subphase ionic composition and surface pressure of the monolayer, including phase transition domains. 1 : 100).

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“…Thus, the points represent temperature dependence of the tension of the monolayer that was at equilibrium with liposomes at just above their tm-C, where B and C are constants. That such behavior is due to a property of the monolayer and is not a consequence of the procedure by which it was generated is indicated by the fact that ir-A compression isotherms for Myr2-PtdCho obtained in other laboratories (11)(12)(13), when replotted as or-F, also exhibit linear relationships in which a break occurs in the region of [10][11][12][13][14][15] dynes/cm. Moreover, examination of literature data on polar lipids reveals this behavior to be quite common except when the acyl chains are highly heterogeneous.…”

Section: Methodsmentioning

confidence: 99%

“…There is some controversy regarding equilibrium pressures of monolayers below the lipid phase-transition temperature (13,19,20). In our experience, the rate of equilibration is strongly influenced by the purity of the lipid and the method of sample preparation (see also ref.…”

Section: Methodsmentioning

confidence: 99%

Lipid monolayer states and their relationships to bilayers.

MacDonald¹,

Simon²

1987

Proc. Natl. Acad. Sci. U.S.A.

158

133

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Uncommon methods of formation and analysis of lipid monolayers have enabled the recognition of several monolayer states and the identification of that in which molecular organization corresponds closely to that of the bilayer. Monolay-ers were formed by continuously adding a solution ofphospholipid [dimyristoyl phosphatidylcholine in hexane/ethanol, 9:1 (vol/ vol)] to the air/water interface of a constant-area trough. This procedure generates unconventional surface pressure (X7)-surface concentration (1) isotherms, which for liquid-crystalline monolayers consist of straight lines with three prominent intersections, two of which are not apparent in conventional n-A isotherms. The regions of linear change of v are explicable in terms of the area dependence of alkyl chain entropy. The two breaks at lower a delimit states in which both chains lie parallel to the surface. The third occurs at collapse, which corresponds to a true equilibrium for unstressed liposomes. Mechanical and thermodynamic properties of bilayers, particularly phase-transition parameters, correspond closely to those of monolayers with which they are in equilibrium.Monolayers of amphiphilic substances at air/water interfaces are of interest in a variety of disciplines. In physics and chemistry, the interest is in understanding the origin and magnitude of the molecular interactions of a single layer of complex molecules positioned between two fluids (1, 2). In biology, monolayers have been important since Gorter and Grendel first proposed the bilayer as the foundation ofbiological membranes (3). Their conclusion was based on an entirely arbitrary compression of a monolayer of lipid extracted from red cells. The critical question of the appropriate compression and, hence, of the relationship between molecular packing in monolayers and that in bilayers remains unanswered.Using an uncommon constant-area procedure to generate surface pressure (7r)-surface concentration (F) isotherms of dimyristoyl phosphatidylcholine (Myr2-PtdCho) monolayers, we have found that the monolayer states of this lipid are characterized by linear regions in the isotherms. There are four such states, and these can be analyzed in terms of their molecular organization. The most condensed state exists in equilibrium with bilayers, and its properties correspond closely to half of a bilayer. This identification is critical for understanding many bilayer properties and is important for membrane reconstitution (4). MATERIALS AND METHODSMyr2-PtdCho, purchased from Avanti Polar Lipids and from Sigma, was dissolved in 9:1 (vol/vol) hexane or pentane/ ethanol to a concentration of 0.5 mg/ml. Lipid solution concentrations given are nominal; accurate values were determined by phosphate assay according to a modification of the Bartlett procedure (5). Absolute ethanol was treated with activated charcoal and distilled. Hexane and pentane were passed through a column of activated alumina. Distilled and deionized water was charcoal-filtered, redeionized, and redistilled. Reagent grade ...

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Equilibrium and metastable states in lecithin films

Cited by 71 publications

References 20 publications

Path Dependence of Adsorption Behavior of Mixtures Containing Dipalmitoyl Phosphatidylcholine

Path Dependence of Adsorption Behavior of Mixtures Containing Dipalmitoyl Phosphatidylcholine

A Fluorescence Approach of the Determination of Translational Diffusion Coefficients of Lipids in Phospholipid Monolayer at the Air-Water Interface

Lipid monolayer states and their relationships to bilayers.

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