Spherical lipid bilayer membranes: Electrical and isotopic studies of ion permeability

Pagano, R. E.; Thompson, T. E.

doi:10.1016/0022-2836(68)90127-7

Cited by 82 publications

(58 citation statements)

References 30 publications

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“…This is consistent with the inside-negative potential across the plasmalemma of some -116 mV (Raven, 1967), and a finite permeability to IAA~. While the passive permeability of model bilayers to Cl~ is only of the order of io~*°cms~* (Pagano and Thompson, 1968), the permeability to larger, lipophilic anions is much larger (estimated at io~^ cms~^ for tetraphenylboron" and CCCP": LeBlanc, 1969LeBlanc, , 1971. The data of Bean, Sheppard and Chan (1968) on the pH dependence of apparent P,AA in such bilayers suggests that PIAA" is not more than 1% of PIAA; LeBlanc (1971) suggests that PCCCP is 10' * times PCCCP"-If PIAA" is put at io"^cms"\ and PIAA at io"''cms~* for the plasmalemma of H. africanum, then distribution of IAA at flux equilibrium will be described by taking the sum of the net passive influx of IAA and the net passive efflux of IAA~ as being zero: between cytoplasm and vacuole (ignoring pH variations in the cytoplasm, e.g.…”

Section: Permeability Of H 2ifnc2itmm Plasmalemma To Iaa and Iaatsupporting

confidence: 78%

TRANSPORT OF INDOLEACETIC ACID IN PLANT CELLS IN RELATION TO pH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT

1975

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SUMMARYThe distribution of IAA between the vacuole and the bathing solution in Hydrodictyon africanum is consistent with passive entry of undissociated IAA and passive efflux of both undissociated IAA and of IAA", with Pi^^ (permeability coefficient)* about io~^ cms~^ and PIAA-about io~^ cms~^ The involvement of IAA~ in the efflux results from the inside-negative P.D. between the medium and the vacuole. The cytoplasm is at a higher pH than either the vacuole or the bathing solution used in most experiments; this is maintained by active H"*" efflux at the plasmalemma, and active influx at the tonoplast. In this situation the efflux of IAA" is further promoted by the increased concentration of IAA" in the relatively alkaline cytoplasm. Thus the apparent active efflux of IAA from these cells can be explained in terms of passive driving forces of concentration and electrical potential acting on IAA and IAA~, with the distribution of these two species dictated ultimately by PI^A, PIAA-> the pH of the various compartments and the electrical potential difference between them. If PIAA/^IAA-were larger at the apical than at the basal end of coleoptile cells, such an effect could explain polar IAA transport, with metabolic energy being used only to maintain the relative permeabilities to the two species, the pH gradient and the electrical gradient.

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Section: Permeability Of H 2ifnc2itmm Plasmalemma To Iaa and Iaatsupporting

confidence: 78%

TRANSPORT OF INDOLEACETIC ACID IN PLANT CELLS IN RELATION TO pH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT

1975

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“…The plot exhibited the linear relationship in the explored temperature ranges. In previous studies, authors reported about 10.7 and 4.1 kcal/mole energy of activation after application of PC-based liposomal formulation across rat skin and human skin, respectively (Pagano & Thompson, 1968;Monti et al, 1995). In this study, the energy was 3.8 kcal/mole for ELA-3 gel indicating 2.63-and 2-fold higher as compared to the DS and EL3-S80, respectively.…”

Section: Assessment Of the Activation Energymentioning

confidence: 46%

Optimized permeation enhancer for topical delivery of 5-fluorouracil-loaded elastic liposome using Design Expert: part II

et al. 2015

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Objective: To prepare and optimize the topical elastic liposome (EL)-loaded carbopol-980 gel of 5-Fluorouracil (5-FU) containing permeation enhancers (azone, propylene glycol (PG) and lauryl alcohol (LA)) and further evaluation for permeation flux of 5-FU, the activation energy and irritation in the rat skin. Methods: EL formulations were prepared using phosphatidylcholine and varied surfactants (Span 60, Span 80 and Tween-80) by rotator evaporation method and optimized by experimental design. In vitro characterizations dictated the EL containing Span 80 (lipid:surfactant ¼ 7:3) (EL3-S80) for further optimization of gel. Different gel formulations (5% w/w) with varying concentration (1-3%) of permeation enhancers were prepared and evaluated for viscosity, spreadability, the 5-FU permeation and deposition. The activation energy using the Franz diffusion cell and the plausible irritation using the Draize test were assessed on the albino rat and rabbit, respectively. Results and discussion: EL3-S80 was selected as an optimized EL owing to maximum desirability (0.99) and enhanced 5-FU flux (187.86 ± 14.1 mg/cm 2 /h). EL3-S80 suspension loaded gels (0.5%) revealed reduced viscosity leading to higher spreadability than blank gel. EL containing 3% azone in gel, EL containing 3% LA in gel and EL containing 3% PG in gel portrayed 187.86 ± 14.1, 117.7 ± 13.4 and 106.7 ± 7.3 mg/cm 2 /h as enhanced 5-FU flux values, respectively as compared to drug solution (8.8 ± 0.76 mg/cm 2 /h). Furthermore, reduced value of activation energy (2.63-folds) and the non-irritancy of gel could be effective and safe. Conclusion: ELA-3 gel formulation could be used as an effective and economic gel in cutaneous cancer and skin-related keratoses.

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“…Indeed, a number of important membrane-associated functions including facilitated diffusion [15], cation discrimination [21], and electrical excitability [12] have been observed in synthetic lipid bilayer membranes separating two aqueous phases either in unmodified systems or in membranes…”

Section: (Chol) or Glyceryl Monostearate (Gms) It Was Found That [Gmmentioning

confidence: 99%

The molecular composition of some lipid bilayer membranes in aqueous solution

1972

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Summary. An analytical technique is described for direct determination of the molecular composition of lipid bilayer membranes in aqueous solution. Membranes formed from chemically pure, radioactively labeled components, were sampled by pipetting a mercury droplet through the bilayer-water interface. During this procedure, the membrane remains intact but decreases in area with a concomitant increase in the area of the surrounding bulk phase. It is shown that each mercury droplet is covered with a fragment of the bilayer membrane in the form of a closed vesicle. The chemical composition of the bilayer is determined from an analysis of the readioactivity on the mercury droplet.Bilayers generated from glyceryl monooleate in n-decane or n-hexadecane contain (4.7 -1-0.4) x 1014 molecules of monoglyceride per cm 2 and a minimum of (2.8; ___ 0.7) x 1014 molecules of solvent (n-hexadecane) per cm 2. It is estimated from these numbers that 37 vol % of the hydrocarbon core of the bilayer is occupied by solvent.The composition relationships between the bilayer and bulk membrane-forming solution were determined for mixtures of glyceryl monooleate (GMO) with cholesterol (Chol) or glyceryl monostearate (GMS). It was found that [GMS/GMO]bilayer-----[GMS/GMOlbulk, and [Chol/GMO]bilayer=0.5[Chol/GMO]bul k. While the molecular areas of glyceryl monooleate and glyceryl monostearate are unchanged in the mixed system, the average area for mixtures of cholesterol and glyceryl monooleate is decreased, suggesting a condensing effect of the sterol in the bilayer analogous to that observed in lipid monolayers.Extensive studies on phospholipid model systems in aqueous solution [16,19] and the recent use of physical techniques to probe the organization of natural membranes [11,18] strongly support the existence of a bimolecular lipid lamella as a mosaic element in many biological membranes [8]. Indeed, a number of important membrane-associated functions including facilitated diffusion [15], cation discrimination [21], and electrical excitability [12] have been observed in synthetic lipid bilayer membranes separating two aqueous phases either in unmodified systems or in membranes

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Spherical lipid bilayer membranes: Electrical and isotopic studies of ion permeability

Cited by 82 publications

References 30 publications

TRANSPORT OF INDOLEACETIC ACID IN PLANT CELLS IN RELATION TO pH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT

TRANSPORT OF INDOLEACETIC ACID IN PLANT CELLS IN RELATION TO pH AND ELECTRICAL POTENTIAL GRADIENTS, AND ITS SIGNIFICANCE FOR POLAR IAA TRANSPORT

Optimized permeation enhancer for topical delivery of 5-fluorouracil-loaded elastic liposome using Design Expert: part II

The molecular composition of some lipid bilayer membranes in aqueous solution

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