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Ethanol Oxidation (ethanol + oxidation)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Effect of Enzyme and Cofactor Immobilization on the Response of Ethanol Oxidation in Zirconium Phosphate Modified Biosensors

ELECTROANALYSIS, Issue 10 2010
Mitk'El
Abstract Two different self-contained ethanol amperometric biosensors incorporating layered [Ru(phend)2bpy]2+ -intercalated zirconium phosphate (ZrP) as the mediator as well as yeast -alcohol dehydrogenase (y- ADH) and its cofactor nicotinamide adenine dinucleotide (NAD+) were constructed to improve upon a design previously reported where only this mediator was immobilized in the surface of a modified electrode. In the first biosensor, a [Ru(phend)2bpy]2+ -intercalated ZrP modified carbon paste electrode (CPE) was improved by immobilizing in its surface both y- ADH and NAD+ using quaternized Nafion membrane. In the second biosensor, a glassy carbon electrode was modified with [Ru(phend)2bpy]2+ -intercalated ZrP, y- ADH, and NAD+ using Nafion as the holding matrix. Calibration plots for ethanol sensing were constructed in the presence and absence of ZrP. In the absence of ZrP in the surface of the modified glassy carbon electrode, leaching of ADH was observed as detected by UV-vis spectrophotometry. Ethanol sensing was also tested in the presence and absence of ascorbate to measure the selectivity of the sensor for ethanol. These two ethanol biosensors were compared to a previously reported one where the y -ADH and the NAD+ were in solution, not immobilized. [source]

Michaelis-Menten Elimination Kinetics of Acetaldehyde During Ethanol Oxidation

ALCOHOLISM, Issue 2002
Tatsuya Fujimiya
Background Acetaldehyde (AcH) is a toxic metabolite of ethanol (EtOH). The pharmacokinetics of blood AcH during EtOH oxidation was studied with or without the administration of aldehyde dehydrogenase 2 inhibitor (cyanamide) in rabbits. Methods An bolus of EtOH saline solution (0.25, 0.5, 1.0, 1.5, and 2.0 g/kg) was injected intravenously. Cyanamide was administered intraperitoneally (25 mg/kg body weight) to the cyanamide-treated group. Blood EtOH and AcH concentrations were measured by using head-space gas chromatography. Results In the control group, the first peak of the blood AcH appeared immediately and the second elevation appeared 1 to 4 hr after administration at a high EtOH dose. The blood AcH levels other than the second elevation part were significantly correlated to the blood EtOH levels. In the cyanamide-treated group, a peak and a plateau formed at the time corresponding to the second peak in the control group. The peak and plateau concentration of AcH increased markedly. We attempted simultaneous curve fitting, using the five blood EtOH and AcH concentration-time curves, to determine the pharmacokinetic model. Consequently, the AcH elimination was best described by a Michaelis-Menten kinetic model in both groups. Conclusions The blood AcH profile was suggested to consist of the first and second components that are related to the blood EtOH concentration itself and the metabolic formation of AcH, respectively. With higher EtOH doses or aldehyde dehydrogenase 2 inhibition, the second component becomes prominent as a result of the capacity-limited property of the metabolism of AcH, which is described by Michaelis-Menten elimination kinetics. [source]

A Metal,Organic Framework as an Electrocatalyst for Ethanol Oxidation

ANGEWANDTE CHEMIE, Issue 31 2010
Lifen Yang
Kein Bedarf an Edelmetallen: Das Kupfer-organische Gerüstmaterial N,N,-Bis(2-hydroxyethyl)dithiooxamidatokupfer(II) (siehe Bild: Cu,rosa, N,blau, S,gelb, O,rot, C,grau, H,weiß) ist ein aktiver Katalysator für die elektrochemische Oxidation von Ethanol. Die Leistung dieses edelmetallfreien Materials ist mit derjenigen von Platin-Katalysatoren vergleichbar. [source]

A New Mechanism for Ethanol Oxidation Mediated by Cytochrome P450 2E1: Bulk Polarity of the Active Site Makes a Difference

CHEMBIOCHEM, Issue 3 2007
Yong Wang
Breaking the habit. A new mechanism, called reversed dual hydrogen abstraction (R-DHA), is presented for ethanol oxidation by cytochrome P450 2E1 (CYP2E1). It is shown that the competition of R-DHA with the consensus mechanism (gem -diol) is modulated by the ethanol population in the enzyme pocket. Thus, as a response to growing blood ethanol level, CYP2E1 adapts its ethanol metabolism by a mechanistic switch from gem -diol to R-DHA. [source]

Influence of Dissolved Oxygen Concentration on the Pharmacokinetics of Alcohol in Humans

ALCOHOLISM, Issue 5 2010
In-hwan Baek
Background:, Ethanol oxidation by the microsomal ethanol oxidizing system requires oxygen for alcohol metabolism, and a higher oxygen uptake increases the rate of ethanol oxidation. We investigated the effect of dissolved oxygen on the pharmacokinetics of alcohol in healthy humans (n = 49). The concentrations of dissolved oxygen were 8, 20, and 25 ppm in alcoholic drinks of 240 and 360 ml (19.5% v/v). Methods:, Blood alcohol concentrations (BACs) were determined by converting breath alcohol concentrations. Breath samples were collected every 30 min when the BAC was higher than 0.015%, 20 min at BAC ,0.015%, 10 min at BAC ,0.010%, and 5 min at BAC ,0.006%. Results:, The high dissolved oxygen groups (20, 25 ppm) descended to 0.000% and 0.050% BAC faster than the normal dissolved oxygen groups (8 ppm; p < 0.05). In analyzing pharmacokinetic parameters, AUCinf and Kel of the high oxygen groups were lower than in the normal oxygen group, while Cmax and Tmax were not significantly affected. In a Monte Carlo simulation, the lognormal distribution of mean values of AUCinf and t1/2 was expected to be reduced in the high oxygen group compared to the normal oxygen group. Conclusions:, In conclusion, elevated dissolved oxygen concentrations in alcoholic drinks accelerate the metabolism and elimination of alcohol. Thus, enhanced dissolved oxygen concentrations in alcohol may have a role to play in reducing alcohol-related side effects and accidents. [source]

Alcohol and Colorectal Cancer: The Role of Alcohol Dehydrogenase 1C Polymorphism

ALCOHOLISM, Issue 3 2009
Nils Homann
Background:, Chronic alcohol consumption is a risk factor for colorectal cancer. Animal experiments as well as genetic linkage studies in Japanese individuals with inactive acetaldehyde dehydrogenase leading to elevated acetaldehyde concentrations following ethanol ingestion support the hypothesis that acetaldehyde may be responsible for this carcinogenic effect of alcohol. In Caucasians, a polymorphism of alcohol dehydrogenase 1C (ADH1C) exists resulting in different acetaldehyde concentrations following ethanol oxidation. Methods:, To evaluate whether the association between alcohol consumption and colorectal tumor development is modified by ADH1C polymorphism, we recruited 173 individuals with colorectal tumors diagnosed by colonoscopy and 788 control individuals without colorectal tumors. Genotyping was performed using genomic DNA extracted from whole blood followed by polymerase chain reaction. Results:, Genotype ADH1C*1/1 was more frequent in patients with alcohol-associated colorectal neoplasia compared to patients without cancers in the multivariate model controlling for age, gender, and alcohol intake (odds ratio = 1.674, 95% confidence interval = 1.110,2.524, 2-sided p from Wald test = 0.0139). In addition, the joint test of the genetic effect and interaction between ADH1C genotype and alcohol intake (2-sided p = 0.0007) indicated that the difference in ADH1C*1 polymorphisms between controls and colorectal neoplasia is strongly influenced by the alcohol consumption and that only individuals drinking more than 30 g ethanol per day with the genotype ADH1C*1/1 had an increased risk for colorectal tumors. Conclusions:, These data identify ADH1C homozygosity as a genetic risk marker for colorectal tumors in individuals consuming more than 30 g alcohol per day and emphasize the role of acetaldehyde as a carcinogenic agent in alcohol-related colorectal carcinogenesis. [source]

Glutamate Export at the Choroid Plexus in Health, Thiamin Deficiency, and Ethanol Intoxication: Review and Hypothesis

ALCOHOLISM, Issue 8 2008
Peter F. Nixon
Introduction:, The earliest observed effect in the pathogenesis of experimental Wernicke's encephalopathy and of ethanol intoxication in rats is impairment of the blood cerebrospinal fluid (CSF) barrier at the choroid plexus (CP). For an explanation, these observations direct attention to the role of the CP in maintaining glutamate homeostasis in the CSF. Methods:, Characteristics of the CP epithelium (CPE) are reviewed, focusing on its role in removal of glutamate from the CSF and its potential for impairment by ethanol oxidation or by thiamin-deficient glucose oxidation. Results:, The export of glutamate from CSF to blood at the CP is energy dependent, saturable, and stereospecific. However, the incapacity of the CP to convert glutamate to other metabolites makes it vulnerable to glutamate accumulation should ,-ketoglutarate dehydrogenase activity be decreased. Elsewhere ethanol metabolism and thiamin-deficiency independently decrease the activity of this mitochondrial enzyme. We argue that they have the same effect within the mitochondria-rich CPE, thereby decreasing energy production necessary for export of glutamate from CSF to blood; diverting its energy metabolism to further glutamate production; and impairing its blood CSF barrier function. This impairment appears to be mediated by glutamate and is attenuated by MK801 but whether it involves one of the CPE glutamate receptors is yet uncertain. This impairment exposes the CSF and hence the paraventricular brain extracellular fluid to neuroactive substances from the blood, including further glutamate, explaining the paraventricular location of neuropathology in Wernicke's encephalopathy. Other organs normally protected from blood by a barrier are affected also by ethanol abuse and by thiamin deficiency, namely the eye, peripheral nerves, and the testis. Much less is known regarding the function of these barriers. Conclusions:, Impairment of the CP by ethanol intoxication and by thiamin-deficient carbohydrate metabolism has a common, rational explanation that can guide future research. [source]

Genetic Repeat Polymorphism in the Regulating Region of CYP2E1: Frequency and Relationship With Enzymatic Activity in Alcoholics

ALCOHOLISM, Issue 6 2001
E. Plee-Gautier
Background: Differences in the regulatory region of the CYP2E1 gene could be responsible for the interindividual variation in the cytochrome P-450 2E1 (CYP2E1) involved in ethanol oxidation. Recently, a polymorphic repeat sequence in the human gene was described between ,2178 and ,1945 base pairs. Its frequency seemed to vary among different ethnic populations, and it was suspected to be related to an increased inducibility to further ethanol intake. In the study reported here, the frequency of this polymorphism was investigated in a white French population. Its relationship with the previously described Pst I/Rsa I or Dra I CYP2E1 polymorphisms, alcoholism, alcoholic liver disease, and inducibility of CYP2E1 by ethanol was examined. Methods: The polymorphic region was characterized by polymerase chain reaction in 103 controls, 148 alcoholic subjects without liver diseases, and 98 others with liver cirrhosis. By using in vivo chlorzoxazone (CHZ) metabolism, CYP2E1 phenotype was assessed in 36 non,ethanol-induced subjects (17 controls and 19 withdrawn alcoholics) and in 14 ethanol-induced subjects (10 controls after ingestion of 0.8 g/kg ethanol and four alcoholics with 100 g of daily intake). This phenotype was expressed as the 6-hydroxy CHZ/CHZ ratio. Results: The rare allele frequency was found to be 1.58% in whites (n= 349). Neither significant association with alcoholism or alcoholic liver diseases, nor relationship with the Pst I/Rsa I polymorphism, was observed. But the Dra I polymorphism was more frequent among the heterozygous subjects when compared with wild-type homozygous ones (p < 0.05). The CYP2E1 phenotype was similar in wild-type homozygotes and in heterozygotes at the constitutive level, as well as after induction with ethanol. Conclusions: Our data suggest that CYP2E1 repeat polymorphism does not seem to constitute a major factor for interindividual differences in CYP2E1 expression and susceptibility to alcohol-related disorders in whites. [source]

Influence of a pore-former and PTFE in the performance of the direct ethanol fuel cell

ASIA-PACIFIC JOURNAL OF CHEMICAL ENGINEERING, Issue 1 2009
S. K. Biswas
Abstract The direct ethanol fuel cell (DEFC) is a promising fuel cell device, which could provide power to portable and microelectronic equipment in the future. In the present investigation, the influence of a pore-former, polytetrafluoroethylene (PTFE) and catalyst loadings in the electrocatalyst of the anode on DEFC performance is studied. The decal transfer method is used to prepare the membrane electrode assembly (MEA) using PtRu/C (40:20% by wt) as the anode catalyst, and Pt/C (40% by wt) as the cathode catalyst, a pore-former, PTFE dispersion and Nafion ionomer. The pore-former used is 10% (by wt) NaHCO3 in the catalyst ink during the preparation of MEA. The voltage-current characteristics of DEFC were monitored at different loadings of the catalyst, PTFE and a pore-former in MEA. The DEFC performance improved with the use of a pore-former and higher loading of PTFE in MEA. Higher DEFC performance is obtained because PTFE, along with the network of pores in the anode side allowed easy removal of reaction species, thereby rendering the catalyst site available for ethanol oxidation. Further, the use of a pore-former and PTFE at the anode allowed higher loading of electrocatalyst resulting in an increase in the performance of DEFC. The DEFC, with 1 mg cm,2 of catalyst loading at the anode and cathode, 10% (by wt) NaHCO3 of a pore-former, 20% (by wt) PTFE loading in catalyst ink gives maximum power density of 8.5 mW cm,2 at a current density of 31.3 mA cm,2. Copyright © 2008 Curtin University of Technology and John Wiley & Sons, Ltd. [source]

A New Mechanism for Ethanol Oxidation Mediated by Cytochrome P450 2E1: Bulk Polarity of the Active Site Makes a Difference

Effect of Ionic Liquids on Catalytic Characteristics of Horse Liver Alcohol Dehydrogenase

CHINESE JOURNAL OF CHEMISTRY, Issue 11 2006
Xian-Ai Shi
Abstract The catalytic characteristics of horse liver alcohol dehydrogenase (HLADH) in the systems involving ionic liquids (ILs) (BMIm·Cl, BMIm·Br, BMIm·PF6, BMIm·BF4 BMIm·OTf and EMIm·Cl) were examined. HLADH displayed higher oxidation activity towards ethanol in the systems containing BMIm·Cl, BMIm·Br, EMIm·Cl or BMIm·PF6 with proper content than that in the IL-free buffer. An excessive amount of these ILs in the reaction systems resulted in an obvious decline in enzymatic activity. BMIm·BF4 and BMIm·OTf of any content investigated could considerably inhibit the enzyme. The anions of ILs showed significant effect on the activity, kinetic parameters and activation energy of HLADH-mediated ethanol oxidation. Additionally, BMIm·Cl, BMIm·Br, EMIm·Cl and BMIm·PF6 boosted markedly the thermostability of HLADH, while the enzyme was less thermostable in BMIm·BF4 or BMIm·OTf-containing systems. The associated conformational changes in HLADH caused by ILs were examined by UV technique. [source]