(1/1378) UV irradiation of polycyclic aromatic hydrocarbons in ices: production of alcohols, quinones, and ethers.
Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis. (+info)
(2/1378) Alcohol-induced biphasic inhibition of myosin subfragment 1 K-EDTA-ATPase.
Butanol-induced inhibition of K-EDTA-ATPase of myosin subfragment 1 proceeded by biphasic kinetics, consisting of rapid and slow inactivations. The extent of the rapid inactivation, which was estimated by extrapolating the process of slow inactivation to zero time of the incubation period, was saturated with butanol concentration. Recovery of activity by dilution in the rapid phase indicates that the rapid process is reversible. The slow inactivation was concomitant with a partial denaturation of the 50 kDa domain of S1, which was detected by limited tryptic digestion. Other alcohols (methanol, ethanol, propanol and hexanol) also inhibited the K-EDTA-ATPase in the rapid phase. The Ki decreased with an increase in the number of methylene groups of alcohol. When K-EDTA-ATPase activity in the rapid phase was plotted against viscosity, surface tension or dielectric constant, the curves were different for each of the various alcohol solutions. The rapid inactivation appears to be caused by a binding of the alkyl group to S1, rather than by solvent effects. The kinetics of rapid butanol inhibitions indicate that butanol reduces the maximum activity of ATPase but enhances an apparent affinity of S1 with ATP. These indications suggest that alcohol stabilizes S1.KATP intermediate. The rapid K-EDTA-ATPase inhibition was observed at the same alcohol concentration where S1 Mg-ATPase was activated. (+info)
(3/1378) Microbial oxidation of methane and methanol: isolation of methane-utilizing bacteria and characterization of a facultative methane-utilizing isolate.
A methane-utilizing organism capable of growth both on methane and on more complex organic substrates as a sole source of carbon and energy, has been isolated and studied in detail. Suspensions of methane-grown cells of this organism oxidized C-1 compounds (methane, methanol, formaldehyde, formate); hydrocarbons (ethane, propane); primary alcohols (ethanol, propanol); primary aldehydes (acetaldehyde, propionaldehyde); alkenes (ethylene, propylene); dimethylether; and organic acids (acetate, malate, succinate, isocitrate). Suspensions of methanol-or succinate-grown cells did not oxidize methane, ethane, propane, ethylene, propylene, or dimethylether, suggesting that the enzymatic systems required for oxidation of these substrates are induced only during growth on methane. Extracts of methane-grown cells contained a particulate reduced nicotinamide adenine dinucleotide-dependent methane monooxygenase activity. Oxidation of methanol, formaldehyde, and primary alcohols was catalyzed by a phenazine methosulfate-linked, ammonium ion-requiring methanol dehydrogenase. Oxidation of primary aldehydes was catalyzed by a phenazine methosulfate-linked, ammonium ion-independent aldehyde dehydrogenase. Formate was oxidized by a nicotinamide adenine dinucleotide-specific formate dehydrogenase. Extracts of methane-grown, but not succinate-grown, cells contained the key enzymes of the serine pathway, hydroxypyruvate reductase and malate lyase, indicating that the enzymes of C-1 assimilation are induced only during growth on C-1 compounds. Glucose-6-phosphate dehydrogenase was induced during growth on glucose. Extracts of methane-grown cells contained low levels of enzymes of the tricarboxylic acid cycle, including alpha-keto glutarate dehydrogenase, relative to the levels found during growth on succinate. (+info)
(4/1378) Inhibition of Bacillus subtilis spore germination by various hydrophobic compounds: demonstration of hydrophobic character of the L-alanine receptor site.
L-Alanine-initiated germination of Bacillus subtilis spores was inhibited by various kinds of hydrophobic compounds. Good correlation of inhibitory effect with hydrophobicity of the compound was demonstrated by using regression analysis in which the hydrophobic character was expressed by the partition coefficient in an octyl alcohol-water system. The correlation coefficient for 20 alcohols was 0.959, and that for 19 miscellaneous compounds was 0.906. Regression lines of the alcohols and other hydrophobic compounds were almost identical, showing that hydrophobic interaction played an important role in inhibition. Diphenylamine was one of the most effective inhibitors examined. n-Octyl, n-nonyl, and n-decyl alcohols were the most effective alcohols. The mode of inhibition by diphenylamine and n-octyl alcohol was a "mixed type" (competitive plus noncompetitive type) with respect to L-alanine; that by D-alanine was competitive inhibition. Sites for diphenylamine, n-octyl alcohol, and D-alanine may have overlapped. Inhibition was reversible by washing; heat resistance, stainability, and germination rate of the washed spores remained unaltered. Thus, we confirmed that the inhibition may occur before the initial trigger reaction of germination and that it may be due to the interaction between a hydrophobic compound and a hydrophobic region closely associated with the L-alanine receptor site on the spore. (+info)
(5/1378) Total plasmalogens and O-(acylalkylglycerophosphoryl) ethanolamine from labelled hexadecanol and palmitate during hypoxia and anoxia in rat heart.
By the use of the Langendorff technique, surviving isolated rat hearts were perfused with [1-14 C] palmitate, [1-14C] hexadecanol or [1-14C,1-3H] hexadecanol under normal or anoxic conditions. After perfusion for 30min with either precursor, when oxygenated or in an hypoxic condition, or when 1mM-KCN was included in the system, the heart tissues showed no significant chemical changes in their content of total lipids, total phospholipids or total ethanolamine-containing phospholipids. Changes were observed in the ratio of alkyl-to alk-1-enyl-glycerophosphorylethanolamine in the tissue perfused with N2+CO1 plus CN-. A slight increase from 4.0+/-0.3 to 4.9+/-0.2% in alkyl derivatives and a decrease from 11.2+/-0.4 to 9.4+/-0.3% in alk-1-enyl derivatives was observed. The incorporation of the [14C] palmitate and the [14C] hexadecanol into the recovered phospholipids and plasmalogens was severely decreased in the tissues perfused with CN-: in the hypoxic state only a mild inhibition was observed compared with the oxygenated systems. Considerable 3H from [1-14C, 1-3H] hexadecanol was retained (25-35%) in the alk-1-enylether chains of plasmalogens under both the oxygenated conditions and with CN-, suggesting that the same mechanism of incorporation is operational at high or low O2 concentrations. The results are consistent with an O2-dependent, CN-sensitive step in the biosynthesis of plasmalogens in the rat heart. (+info)
(6/1378) Effects of short chain alkanols on the inducible nitric oxide synthase in a glial cell line.
1. Ethanol inhibits inducible nitric oxide synthase (iNOS) expression in C6 glioma cells by an unknown mechanism. Because relatively high concentrations are needed for inhibition in drug-naive cells (IC50 approximately = to 150 mM), suppression due to cytotoxicity is one possible mechanism that has not been ruled out. Therefore, the present study examined the effects of ethanol and other alkanols on C6 glioma cell viability and iNOS activity to better understand the mechanism for inhibition. 2. iNOS expression was induced in cell culture with lipopolysaccharide and phorbol ester treatment. Nitrite accumulation in culture medium, the in vitro conversion of [3H]-L-arginine to [3H]-L-citrulline, and immunoblotting were used to quantify iNOS induction and activity. Trypan blue exclusion, extracellular release of lactate dehydrogenase, and quantity of total cell protein were used as measures of viability. 3. Short chain alkanols, methanol through 1-heptanol, concentration-dependently inhibited nitrite accumulation. Longer chain alkanols, 1-octanol and 1-decanol, did not except at cytotoxic concentrations. Experiments indicated short chain alkanol inhibition was not due to direct actions on iNOS catalytic activity, but that it transpires during iNOS induction. Immunoblots showed reduced iNOS protein levels. 4. Correlation analysis ruled out iNOS inhibition as being due to decreased cell number, total cell protein, or cell viability. In contrast, there was significant correlation with physical measures of lipophilicity. 5. In conclusion, inhibition of iNOS expression by ethanol and other short chain alkanols is not due to cytotoxicity. Instead, the strong correlation with lipophilicity suggests the inhibition derives from an interaction with unknown hydrophobic cellular sites. (+info)
(7/1378) A low-molecular-mass protein from Methylococcus capsulatus (Bath) is responsible for the regulation of formaldehyde dehydrogenase activity in vitro.
An 8.6 kDa protein, which the authors call a modifin, has been purified from Methylococcus capsulatus (Bath) and has been shown to alter the substrate specificity and kinetics of NAD+-linked formaldehyde dehydrogenase (FDH) isolated from the same organism. Purification methods for both the modifin and FDH are presented which reliably produced pure protein for further analysis. Analysis of the molecular mass and N-terminal sequence of both FDH and the modifin indicate that they are unique proteins and show no similarity to alcohol or aldehyde dehydrogenase enzymes isolated from methylotrophic bacteria. Substrate specificity studies demonstrated that FDH oxidized formaldehyde exclusively in the presence of the modifin; a diverse range of aldehydes and alcohols were oxidized by FDH in the absence of the modifin. No formaldehyde oxidation was detected in the absence of the modifin. Attempts to replace the modifin with glutathione or high concentrations of methanol to stimulate formaldehyde oxidation failed. With acetaldehyde as substrate, FDH showed standard Michaelis-Menten kinetics; interaction of FDH with the modifin using formaldehyde as substrate altered the kinetics of the reaction to sigmoidal. Kinetic analysis during turnover experiments indicated that the FDH may be associated with bound formaldehyde following enzyme isolation and that NAD may also be associated with the enzyme but in a form that is less tightly bound than found with the methanol dehydrogenase from Bacillus methanolicus. Data are presented which indicate that the modifin may play an important role in regulating formaldehyde concentration in vivo. (+info)
(8/1378) Oxidation of medium-chain acyl-CoA esters by extracts of Aspergillus niger: enzymology and characterization of intermediates by HPLC.
The activities of beta-oxidation enzymes were measured in extracts of glucose- and triolein-grown cells of Aspergillus niger. Growth on triolein stimulated increased enzyme activity, especially for acyl-CoA dehydrogenase. No acyl-CoA oxidase activity was detected. HPLC analysis after incubation of triolein-grown cell extracts with decanoyl-CoA showed that beta-oxidation was limited to one cycle. Octanoyl-CoA accumulated as the decanoyl-CoA was oxidized. Beta-oxidation enzymes in isolated mitochondrial fractions were also studied. The results are discussed in the context of methyl ketone production by fungi. (+info)