Ethanol membrane interactions

C. D. Stubbs, B. W. Williams, C. L. Pryor, and E. Rubin, Ethanol-induced modifications to membrane lipid structure—Effect on phospholipase A2-membrane interactions, Arch. Biochem. 262, 560-573 (1988). 

Vapor permeation and pervaporation are membrane separation processes that employ dense, non-porous membranes for the selective separation of dilute solutes from a vapor or liquid bulk, respectively, into a solute-enriched vapor phase. The separation concept of vapor permeation and pervaporation is based on the molecular interaction between the feed components and the dense membrane, unlike some pressure-driven membrane processes such as microfiltration, whose general separation mechanism is primarily based on size-exclusion. Hence, the membrane serves as a selective transport barrier during the permeation of solutes from the feed (upstream) phase to the downstream phase and, in this way, possesses an additional selectivity (permselectivity) compared to evaporative techniques, such as distillation (see Chapter 3.1). This is an advantage when, for example, a feed stream consists of an azeotrope that, by definition, caimot be further separated by distillation. Introducing a permselective membrane barrier through which separation is controlled by solute-membrane interactions rather than those dominating the vapor-liquid equilibrium, such an evaporative separation problem can be overcome without the need for external aids such as entrainers. The most common example for such an application is the dehydration of ethanol. 

In a subsequent communication, Elliott and coworkers found that uniaxially oriented membranes swollen with ethanol/water mixtures could relax back to an almost isotropic state. In contrast, morphological relaxation was not observed for membranes swollen in water alone. While this relaxation behavior was attributed to the plasticization effect of ethanol on the fluorocarbon matrix of Nafion, no evidence of interaction between ethanol and the fluorocarbon backbone is presented. In light of the previous thermal relaxation studies of Moore and co-workers, an alternative explanation for this solvent induced relaxation may be that ethanol is more effective than water in weakening the electrostatic interactions and mobilizing the side chain elements. Clearly, a more detailed analysis of this phenomenon involving a dynamic mechanical and/ or spectroscopic analysis is needed to gain a detailed molecular level understanding of this relaxation process. 

Haloalkanes. Certain haloalkanes and haloalkane-containing mixtures have been demonstrated to potentiate carbon tetrachloride hepatotoxicity. Pretreatment of rats with trichloroethylene (TCE) enhanced carbon tetrachloride-induced hepatotoxicity, and a mixture of nontoxic doses of TCE and carbon tetrachloride elicited moderate to severe liver injury (Pessayre et al. 1982). The researchers believed that the interaction was mediated by TCE itself rather than its metabolites. TCE can also potentiate hepatic damage produced by low (10 ppm) concentrations of carbon tetrachloride in ethanol pretreated rats (Ikatsu and Nakajima 1992). Acetone was a more potent potentiator of carbon tetrachloride hepatotoxicity than was TCE, and acetone pretreatment also enhanced the hepatotoxic response of rats to a TCE-carbon tetrachloride mixture (Charbonneau et al. 1986). The potentiating action of acetone may involve not only increased metabolic activation of TCE and/or carbon tetrachloride, but also possible alteration of the integrity of organelle membranes. Carbon tetrachloride-induced liver necrosis and lipid peroxidation in the rat has been reported to be potentiated by 1,2- dichloroethane in an interaction that does not involve depletion of reduced liver glutathione, and that is prevented by vitamin E (Aragno et al. 1992). 

Eszopiclone Bind selectively to a subgroup of GABAa receptors, acting like benzodiazepines to enhance membrane hyperpolarization Rapid onset of hypnosis with few amnestic effects or day-after psychomotor depression or somnolence Sleep disorders, especially those characterized by difficulty in falling asleep Oral activity short half-lives CYP substrates Toxicity Extensions of CNS depressant effects dependence liability Interactions Additive CNS depression with ethanol and many other drugs... 

In order to confirm the possible interaction of ethanol and crocin on NMDA receptors, we also performed whole-cell patch recording with primary cultured hippocampal neurons and measured membrane currents induced by the application of NMDA in a voltage-clamped condition. Application of 100 pM NMDA induced an inward current of 100.2 9.8 pA (n=10) at a holding potential of -60 mV. The NMDA-induced inward current was not affected by 10 pM CNQX (data not shown), but was completely abolished by 30 pM APV, supporting the fact that the response was mediated by NMDA receptors. Ethanol inhibited NMDA-induced currents in a concentration-dependent manner. Crocin (10 pM) had no effect on NMDA-induced currents by itself (data not shown), but attenuated the inhibitory effect of ethanol on NMDA-induced currents. The concentration-effect curve for ethanol was shifted to the right by the presence of crocin [22]. 

Even though our understanding of the possible types of lipid-protein interactions in membranes has developed only recently, it was evident to early investigators that neutral solvents per se were the most effective for isolation purposes. Perhaps the most widely used solvent extraction procedure for many years was that employing a mixture of ethanol-diethyl ether (usually 1 3, v/v). This technique involved extraction of a tissue with this solvent combination for several hours at 55-60°C (Bloor, 1928). However, as more refined techniques were developed for the detection and assay of lipids, it became evident that this solvent (and condition) could have a deleterious... 

Drinlciiig alcohol affects the nervous system in five different ways (1 intoxication (loss of physical coordination) (2) niemory U>ss (blackouts amnesia) (3) tolerance (loss of ability to become intoxicated) (4) addiction (uncontrolled craving) and (5) withdrawal symptoms (seizures and tremors) (Diamond and Gordon, 1997), These five effects may all be due to the interaction of ethanol with membrane-bound proteins of the brain. Ethanol is unique among most metabolites, in that it is both water soluble and lipid soluble. Hence, it has the ability to pass directly from the bioodstream into various regions of the brain. 

Organic acids (lactic, acetic) Bacteriocins co2 Hydrogen peroxide Diacetyl Reuterin Ethanol Increase acidity, antimicrobial compounds Nisin only bacteriocin permitted as food preservative, disrupts cytoplasmic membrane Reduces membrane permeability Oxidizes proteins Interacts with arginine-binding proteins Not confirmed, may interact with thiol group in proteins that may lead to oxidative stress (Whitehead et al., 2008)... 

Stillwell W, Ehringer WD, Wassail SR. Interaction of a-tocopherol with fatty acids in membranes and ethanol. Biochim Biophys Acta 1992 1105 237-244. 

Another option is to place the filtration unit inside the flow cell, as demonstrated in the spectrophotometric flow injection determination of hydrogen peroxide [297]. The analyte interacted with titanium(IV) and 2-((5-bromopyridyl)azo)-5-(N-propyl-N-sulfopropylamino) phenol (PAPS) yielding a red-purple complex. After ion pairing with CTAB, the complex was adsorbed and concentrated on a very small area of the membrane filter positioned inside the flow cell. The analyte was quantified directly in the membrane by solid-phase spectrophotometry (see 4.1.1.4). Thereafter, ethanol was injected in order to solubilise the complex and transport it to waste. 

The solvent effects of 50% ethanol on the system coefficients of the P/W system are shown in Figure 5.1. It shows that the hydrophobicity was regulated downward that is, the contribution of the hydrophobicity to the partition coefficient was reduced by the addition of ethanol. This is theoretically expected because the addition of ethanol into the water solution will increase the hydrophobicity of the solution and consequendy reduce the hydrophobicity difference between the PDMS and water solution. If the hydrophobicity of the solution and the PDMS membrane are the same, the hydrophobicity interactions of the compounds with the membrane and the solution will have no contribution to the partition coefficient. The contributions of hydrogen bond basicity Aa and acidity Afc are both increased. These observations revealed that hydrogen-bonding interactions became more important as the ethanol proportion increased. These results demonstrated that the system coefficient approach is not only quantitative but also quahtative it allows the contributions of each type of molecular interaction to be analyzed. The system coefficient approach has high sensitivity in detecting the solvent effects. When the ethanol content... 

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