Permeation of Aromatic Carboxylic Acids across Lipid Bilayers: The pH-Partition Hypothesis Revisited

Thomae, Anita V.; Wunderli‐Allenspach, Heidi; Krämer, Stefanie-Dorothea

doi:10.1529/biophysj.105.060871

Cited by 70 publications

(86 citation statements)

References 32 publications

(32 reference statements)

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“…The data were taken from ref. [30]. Membrane diffusion of weak acids and bases includes the following steps (from left to right): 1) Diffusion through the left UL; 2) Proton uptake or proton release for weak acids or bases, respectively, at the membrane-water interface to form the neutral form of the weak acid/base; 3) Only the uncharged species passes the lipid bilayer as the charged species is facing the Born energy barrier.…”

Section: Discussionmentioning

confidence: 99%

“…From the octanol water partition coefficient K p ≈300, [31] Equation (1) (3) that is, the difference between P M,SA− and P M,SA should be three orders of magnitude larger than has been reported. [30] The reason for the discrepancy between theory and experiment becomes evident, if the limitations of the experimental approach are considered. SA uptake into liposomes with a diameter of d = 200 nm was monitored by following its complex formation with intravesicular Tb 3+ ( Figure 3).…”

Section: Aromatic Weak Acidsmentioning

confidence: 99%

“…This is true both for the "old fashioned" model [32] operating according to the Meyer-Overton rule and for the new stopped-flow-based model according to which the transmembrane diffusion of the deprotonated form was claimed to significantly contribute to the total SA flux. [30] The proton is released again at the other side of the membrane as the pH value of the solution is several units above the pK value of SA. Both the pH increase at the SA donating site of the membrane and the acidification at the receiving site can be measured with pH-sensitive microelectrodes ( Figure 5), which scan the UL in the direction perpendicular to the membrane.…”

Section: Aromatic Weak Acidsmentioning

confidence: 99%

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110 Years of the Meyer–Overton Rule: Predicting Membrane Permeability of Gases and Other Small Compounds

2009

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The transport of gaseous compounds across biological membranes is essential in all forms of life. Although it was generally accepted that gases freely penetrate the lipid matrix of biological membranes, a number of studies challenged this doctrine as they found biological membranes to have extremely low gas-permeability values. These observations led to the identification of several membrane-embedded "gas" channels, which facilitate the transport of biological active gases, such as carbon dioxide, nitric oxide, and ammonia. However, some of these findings are in contrast to the well-established solubility-diffusion model (also known as the Meyer-Overton rule), which predicts membrane permeabilities from the molecule's oil-water partition coefficient. Herein, we discuss recently reported violations of the Meyer-Overton rule for small molecules, including carboxylic acids and gases, and show that Meyer and Overton continue to rule.

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Section: Discussionmentioning

confidence: 99%

Section: Aromatic Weak Acidsmentioning

confidence: 99%

Section: Aromatic Weak Acidsmentioning

confidence: 99%

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110 Years of the Meyer–Overton Rule: Predicting Membrane Permeability of Gases and Other Small Compounds

2009

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“…The question of anion transport across membranes remains puzzling (8). However, Thomae et al (50), who recently investigated the permeation of weak acids across lipid bilayers, may have provided a rationale for this conundrum. They found that small amphiphilic anions do indeed permeate across bilayers but at a much slower rate than the uncharged form of the acid.…”

Section: Discussionmentioning

confidence: 99%

Artificial sweeteners and salts producing a metallic taste sensation activate TRPV1 receptors

Riera¹,

Vogel²,

Simon³

et al. 2007

American Journal of Physiology-Regulatory, Integrative and Comp

112

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Riera CE, Vogel H, Simon SA, le Coutre J. Artificial sweeteners and salts producing a metallic taste sensation activate TRPV1 receptors. Am J Physiol Regul Integr Comp Physiol 293: R626-R634, 2007. First published June 13, 2007; doi:10.1152/ajpregu.00286.2007.-Throughout the world many people use artificial sweeteners (AS) for the purpose of reducing caloric intake. The most prominently used of these molecules include saccharin, aspartame (Nutrasweet), acesulfame-K, and cyclamate. Despite the caloric advantage they provide, one key concern in their use is their aversive aftertaste that has been characterized on a sensory level as bitter and/or metallic. Recently, it has been shown that the activation of particular T2R bitter taste receptors is partially involved with the bitter aftertaste sensation of saccharin and acesulfame-K. To more fully understand the biology behind these phenomena we have addressed the question of whether AS could stimulate transient receptor potential vanilloid-1 (TRPV1) receptors, as these receptors are activated by a large range of structurally different chemicals. Moreover, TRPV1 receptors and/or their variants are found in taste receptor cells and in nerve terminals throughout the oral cavity. Hence, TRPV1 activation could be involved in the AS aftertaste or even contribute to the poorly understood metallic taste sensation. Using Ca 2ϩ imaging on TRPV1 receptors heterologously expressed in the human embryonic kidney (HEK) 293 cells and on dissociated primary sensory neurons, we find that in both systems, AS activate TRPV1 receptors, and, moreover, they sensitize these channels to acid and heat. We also found that TRPV1 receptors are activated by CuSO 4, ZnSO4, and FeSO4, three salts known to produce a metallic taste sensation. In summary, our results identify a novel group of compounds that activate TRPV1 and, consequently, provide a molecular mechanism that may account for off tastes of sweeteners and metallic tasting salts. multisensory taste; pain; calcium imaging IN MANY FOODS, ARTIFICIAL sweeteners (AS) represent a major dietary supplement. Their consumption is involved with weight management, prevention of dental decay, and for diabetics the control of blood glucose. Saccharin, aspartame, and acesulfame-K are among the most commonly used AS. Cyclamate, although currently not approved for use in the United States, is used in more than 50 countries worldwide. Unlike sucrose, these compounds are not perceived to be sweet at all concentrations. In fact, for all these compounds, as concentration increases, the taste perception shifts from pleasant (sweet) toward unpleasant (bitter/metallic) (10,12,41). This shift has been explained by the activation at low concentrations of sweet tastant-sensing G protein-coupled receptors (GPCRs) T1R2/ T1R3 (23) and at higher concentrations, the activation of the bitter tastant sensing GPCRs, T2R43, and T2R44 for saccharin and acesulfame-K (21). Other taste sensations related to the aftertaste elicited by artificial sweeteners have been attributed ...

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“…It is assumed that only the neutral form of an acid or a base can permeate lipid bilayers (23,24). However, recently the pH-partition hypothesis was contradicted by demonstrating the permeation of aromatic carboxylic acids (where the FDA derivative carboxyfluorescein diacetate (cFDA) belongs) as a function of pH (25). At physiological pH the tested acids exist mainly in its anionic (charged) state.…”

Section: Fluorogenic Substratesmentioning

confidence: 99%

Viability states of bacteria—Specific mechanisms of selected probes

2010

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Single cell techniques like flow cytometry combined with viability staining can help to obtain information on viability states of bacteria. Many fluorescent dyes are available for this purpose and can be chosen according to the available excitation source, the species used, and the background of scientific questions and relevant specifications. Within this short overview, we focus on two diverse groups of bacteria: the gram2 Escherichia coli and representatives of the gram+ Mycobacterium to demonstrate differences and similarities in dye uptake principles, processing and binding. We call for attention to possible diverse responses of different species to various viability assays. The cell surface structure of bacteria and the chemical properties of fluorescent probes considerably determine the success of a certain staining practice. Particular focus was drawn on analysis of membrane integrity, uptake of substrates and transformation of fluorogenic substrates. '

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Permeation of Aromatic Carboxylic Acids across Lipid Bilayers: The pH-Partition Hypothesis Revisited

Cited by 70 publications

References 32 publications

110 Years of the Meyer–Overton Rule: Predicting Membrane Permeability of Gases and Other Small Compounds

110 Years of the Meyer–Overton Rule: Predicting Membrane Permeability of Gases and Other Small Compounds

Artificial sweeteners and salts producing a metallic taste sensation activate TRPV1 receptors

Viability states of bacteria—Specific mechanisms of selected probes

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