Nuclear magnetic resonance determinations of permeation coefficients for maleic acid in phospholipid vesicles

Prestegard, James H.; Cramer, John A.; Viscio, David B.

doi:10.1016/s0006-3495(79)85272-8

Cited by 21 publications

(14 citation statements)

References 9 publications

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“…2A, oleic acid was added in the presence of both albumin and SUVs. After the first addition of oleic acid (20 nmol), pH,,, decreased only slightly, in contrast to the pH decrease of 0.22 unit observed after addition of 20 nmol of oleic acid in the absence of BSA (Fig. 1B).…”

Section: Resultsmentioning

confidence: 65%

“…The protonation and deprotonation reactions are assumed to be extremely fast, as for protonophores (30). Our (20), bile acids (21), and phosphatidic acid (32)] showing rapid transbilayer movement of the un-ionized (uncharged) form compared with the ionized (charged) form. This study reveals fundamental properties of long-chain fatty acids in phospholipid bilayers, the structural framework of most cell membranes.…”

Section: Resultsmentioning

confidence: 82%

“…Using phospholipid vesicles as model membranes, Doody et al (17) concluded that the flip-flop of fluorescently-labeled fatty acids was more rapid than transfer between vesicles, whereas Storch and Kleinfeld (18) reached the opposite conclusion. Moreover, the latter study suggested that the rate of flip-flop was faster for ionized than for un-ionized fluorescently-labeled fatty acids (18), contrary to what might be expected (16,(19)(20)(21). Native long-chain fatty acids are completely removed from vesicles by albumin within seconds (22) or minutes (19), suggesting flip-flop of fatty acids within the time resolution of these measurements.…”

mentioning

confidence: 87%

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pH gradients across phospholipid membranes caused by fast flip-flop of un-ionized fatty acids.

Kamp

Hamilton

1992

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

284

290

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A central, unresolved question in cell physiology is how fatty acids move across cell membranes and whether protein(s) are required to facilitate transbilayer movement. We have developed a method for monitoring movement of fatty acids across protein-free model membranes (phospholipid bilayers). Pyranin, a water-soluble, pH-sensitive fluorescent molecule, was trapped inside well-sealed phosphatidylcholine vesicles (with or without cholesterol) in Hepes buffer (pH 7.4). Upon addition of a long-chain fatty acid (e.g., oleic acid) to the external buffer (also Hepes, pH 7.4), a decrease in fluorescence of pyranin was observed immediately (within 10 sec). This acidification of the internal volume was the result of the "flip" of un-ionized fatty acids to the inner leaflet, followed by a release ofprotons from -50% of these fatty acid molecules (apparent pKa in the bilayer = 7.6). The proton gradient thus generated dissipated slowly because of slow cyclic proton transfer by fatty acids. Addition of bovine serum albumin to vesicles with fatty acids instantly removed the pH gradient, indicating complete removal of fatty acids, which requires rapid "flop" of fatty acids from the inner to the outer monolayer layer. Using a four-state kinetic diagam of fatty acids in membranes, we conclude that un-ionized fatty acid flip-flops rapidly (t,/2 s 2 sec) whereas ionized fatty acid flip-flops slowly (t112 of minutes). Since fatty acids move across phosphatidylcboline bilayers spontaneously and rapidly, complex mechanisms (e.g., transport proteins) may not be required for translocation of fatty acids in biological membranes. The proton movement accompanying fatty acid ifip-flop is an important consideration for fatty acid metabolism in normal physiology and in disease states such as cardiac ischemia.Unesterified fatty acids are a key intermediate in lipid metabolism. In the well-oxygenated heart, fatty acids constitute the primary fuel, and the availability of fatty acids in plasma is a controlling factor in the rate of intracellular fatty acid utilization (1). Recently, fatty acids have also been found to have diverse biological activities, serving as second messengers (2), K+ channel activators (3), inhibitors of the binding of plasma low density lipoproteins to receptors (4), and uncouplers of oxidative phosphorylation (5, 6). Fatty acids are either delivered to a membrane [e.g., from serum albumin (7)] or generated within it [e.g., by phospholipase A2 (8)] in one leaflet only. Movement of fatty acids across the membrane may be essential for their utilization.At present there is controversy as to the mechanism and rate of transbilayer movement offatty acids in membranes (7,9). Investigations with cell systems have led to conflicting conclusions, suggesting either rapid passive diffusion ["flipflop" (10)] across the plasma membrane (11, 12) or proteinmediated transport (13-15), although the latter studies have not distinguished whether the protein(s) sequesters fatty acids from the plasma into the membrane or actually tra...

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Section: Resultsmentioning

confidence: 65%

Section: Resultsmentioning

confidence: 82%

mentioning

confidence: 87%

See 1 more Smart Citation

pH gradients across phospholipid membranes caused by fast flip-flop of un-ionized fatty acids.

Kamp

Hamilton

1992

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

284

290

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“…3 are consistent with 5-HT diffusing through the intact membrane from the exterior to the interior of the vesicle. Concentration of an amine on the side of the membrane lowest in pH is characteristic of a system in which the neutral molecule is the only species transported (14). Under these circumstances, a pseudo-equilibrium should be reached in which the neutral species are at approximately equal concentrations on the two sides of the membrane.…”

Section: Discussionmentioning

confidence: 99%

NMR studies of 5-hydroxytryptamine transport through large unilamellar vesicle membranes.

Viscio¹,

Prestegard²

1981

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

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Nuclear magnetic resonance techniques developed to study membrane permeability in closed membrane systems have been used to investigate transport of 5-hydroxytryptamine across the phospholipid membranes of large unilamellar vesicles. The vesicles, modeling the 5-hydroxytryptamine storage organelles of blood platelets, contained a high internal level of ATP buffered at a pH low relative to the external solution. The resultant pH gradient drove accumulation of 5-hydroxytryptamine to a level consistent with selective transport of the neutral amine. The upfield shifts of the 5-hydroxytryptamine resonances resulting from complexation with internally confined ATP were utilized to resolve and, simultaneously, to observe the internal and external amine. Simulation of the time evolution of the 5-hydroxytryptamine concentration allowed measurement of a permeability coefficient of 1.4 ± 0.5 x 10-5 cm/sec for the neutral amine.

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“…Permeation was controlled by the anion at pH 7 and not by the residual neutral acid, as would be expected from the pH -partition hypothesis. There is more evidence for relevant translocation or permeation of charged compounds: significant bilayer translocation of anionic 7-nitrobenzo-1,2,3-oxadiazol-4-yl (NBD)-labeled phosphatidylglycerol was observed [27], and a ratio of 10 4 between maleic acid and maleate monoanion permeation was determined [44]. The question remains how the situation is for bases with pK a values > 7.4.…”

Section: What If Not the Same Process Is Rate-limiting At Low And Higmentioning

confidence: 99%

Lipid‐Bilayer Permeation of Drug‐Like Compounds

Krämer

Lombardi

Primorac

et al. 2009

Chemistry & Biodiversity

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Lipid-bilayer permeation is determinant for the disposition of xenobiotics in the body. It controls the pharmacokinetic behavior of drugs and is, in many cases, a prerequisite for intracellular targeting. Permeation of in vivo barriers is in general predicted from lipophilicity and related parameters. This article goes beyond the empirical correlations, and elucidates the processes and their interplay determining bilayer permeation. A flip-flop model for bilayer permeation, which considers the partitioning rate constants beside the translocation rate constants, is compared with the diffusion model based on Fick's first law. According to the flip-flop model, the ratios of aqueous volumes to barrier area can determine whether partitioning or translocation is rate-limiting. The flip-flop model allows permeation of anions and cations, and expands our understanding of pH-dependent permeation kinetics. Some experimental evidences for ion-controlled permeation at pH 7 are also included in this work.

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Nuclear magnetic resonance determinations of permeation coefficients for maleic acid in phospholipid vesicles

Cited by 21 publications

References 9 publications

pH gradients across phospholipid membranes caused by fast flip-flop of un-ionized fatty acids.

pH gradients across phospholipid membranes caused by fast flip-flop of un-ionized fatty acids.

NMR studies of 5-hydroxytryptamine transport through large unilamellar vesicle membranes.

Lipid‐Bilayer Permeation of Drug‐Like Compounds

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