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PubMedDate not supplied

[Methane formation from pectin by a combined Clostridium pectinofermentans and Methanosarcinia vacuolata culture].

The combined culture of Clostridium pectinofermentans and Methanosarcina vacuolata was shown to be capable of methane production from pectin. Hydrogen, methanol and acetate were methane precursors in that case. C. pectinofermentans grew by 67% better in the combined culture comparing to the pure culture. The stimulating action of M. vacuolata cannot be attributed to the elimination of methanol since it has no effect on the growth of C. pectinofermentans on pectin.

Anaerobiosis↗
PubMed1994

Methane accumulation during closed-circuit anesthesia.

When using the closed-circuit PhysioFlex apparatus for ventilating patients with an O2/air mixture during total intravenous anesthesia (TIVA) for gynecologic laparoscopy, we noticed that the built-in infrared analyzer indicated unexpected values for halothane. In 10 ASA grade I or II patients, the breathing gases were analyzed at the end of the ventilation for the presence of methane, which could be traced in all patients. Mean concentration was 861 ppm after a mean closed-circuit anesthesia time lasting 78 min. The unexpected halothane concentration at the time of gas sampling indicated an average of 1.0%. The anesthetic vapor analysis by infrared absorption is clearly disturbed by the presence of methane.

Adult↗
PubMed1993

Transient intermediates of the methane monooxygenase catalytic cycle.

Three new intermediates of the catalytic cycle of the soluble form of methane monooxygenase (MMO) isolated from Methylosinus trichosporium OB3b have been detected using transient kinetic techniques. MMO consists of hydroxylase (MMOH), reductase, and "B" (MMOB) components. MMOH contains an oxygen-bridged [Fe(III).Fe(III)] cluster that catalyzes O2 activation and insertion chemistry. At 4 degrees C, rapid mixing of O2 with diferrous MMOH ([Fe(II).Fe(II)]) in the presence of a 2-fold excess of MMOB resulted in loss of the g = 16 EPR signal characteristic of the diferrous cluster at an apparent first order rate of 22 +/- 5 s-1 (O2 approximately 700 microM). Subsequently, an EPR silent, chromophoric (lambda max = 330 and 430 nm, epsilon approximately 7500 M-1 cm-1 at each wavelength) intermediate (compound Q) formed with an average first order rate constant of 1 +/- 0.1 s-1 and then decayed at 0.05 +/- 0.01 s-1. Since compound Q formed much more slowly than diferrous MMOH disappeared, at least one other undetected intermediate (compound P) must have formed before compound Q. MMO substrates had little or no effect on the formation rate of compound Q, but they caused the decay rate to increase linearly with the concentration added. The substrates methane, furan, and nitrobenzene caused compound Q decay to occur with second order rate constants of 19,000 M-1 s-1, 9000 M-1 s-1, and 200 M-1 s-1 (+/- 5%), respectively. When nitrobenzene was used as a substrate, a second chromophoric intermediate (compound T, lambda max = 325 nm, with a shoulder at 395 nm, epsilon 395 approximately 6000 M-1 cm-1) formed at the same rate as compound Q decay. Chemical quench studies showed that compound T is an enzyme-product complex that decays with a rate constant of 0.02 +/- 0.005 s-1. This rate is approximately the same as kcat for nitrobenzene turnover at 4 degrees C catalyzed by the reconstituted MMO system, suggesting that product release is the rate-limiting step in catalysis. The characteristics of compound Q suggest that it may be the activated form of the enzyme that directly catalyzes substrate oxidation.

Binding Sites↗
PubMed2002

Reactions of silicon atoms with methane and silane in solid argon: a matrix-spectroscopic study.

The reaction of silicon atoms with methane (1) and silane (7) in argon at 10 K has been studied. Methane (1) is found to be inert to silicon atoms, but reaction occurs upon photochemical excitation under formation of methylsilylene (2). On the contrary, silane (7) is spontaneously converted into a mixture of silylsilylene (10) and disilene (12). Subsequent irradiation generates the butterfly-type disilyne Si(2)H(2) (14), together with a third photoproduct, which we assume to be the doubly bridged Si(2)H(4) isomer 13. The structural elucidation of the new species is based on the comparison of the experimental IR and UV/Vis spectra with data from density functional theory calculations. The results are supported by isotopic labeling studies.

Journal Article↗
PubMed1979

The identification of bile acid methyl esters by gas chromatography methane chemical ionization mass spectrometry.

Methane chemical ionization mass spectrometric data and gas chromatography retention parameters are reported for 31 bile acid methyl esters. The group includes both saturated and unsaturated compounds with up to three keto or hydroxyl groups. Major ions include the quasimolecular ions and fragments resulting from the loss of neutral species such as methanol, water and methane. The combination of gas-liquid chromatography retention and mass spectral data is sufficient for an unequivocal distinction among all the bile acids studied. Application of this data to the identification of bile acid metabolites is cited.

Bile Acids and Salts↗
PubMed2002

Computational studies of reaction mechanisms of methane monooxygenase and ribonucleotide reductase.

An overview of the computational efforts made by our group during the last few years in the field of nonheme diiron proteins is presented. Through application of ab initio methodology to a reasonable set of molecular models, significant progress is made in understanding how the soluble Methane Monooxygenase system achieves the hydroxylation of methane and how the catalytic cycle of Ribonucleotide Reductase is initiated. In particular, the current studies reveal in more detail (1) the nature of key intermediates in the reaction cycles of these two metalloenzymes, (2) details of how the iron centers regulate the systems, and (3) important aspects of how the carboxylate ligands in the active sites may tailor the enzymatic needs of the metalloprotein. This knowledge also leads to novel connections between the two enzymes. The coordinative unsaturation and carboxylate shifts investigated herein are two properties that are likely to be of more general impact in nonheme proteins. The control of the redox chemistry of the enzyme by the binuclear metal center, also analyzed here, should find common ground among other bimetallic systems as well.

Binding Sites↗
PubMed1997

Crystal structure of the hydroxylase component of methane monooxygenase from Methylosinus trichosporium OB3b.

Methane monooxygenase (MMO), found in aerobic methanotrophic bacteria, catalyzes the O2-dependent conversion of methane to methanol. The soluble form of the enzyme (sMMO) consists of three components: a reductase, a regulatory "B" component (MMOB), and a hydroxylase component (MMOH), which contains a hydroxo-bridged dinuclear iron cluster. Two genera of methanotrophs, termed Type X and Type II, which differ markedly in cellular and metabolic characteristics, are known to produce the sMMO. The structure of MMOH from the Type X methanotroph Methylococcus capsulatus Bath (MMO Bath) has been reported recently. Two different structures were found for the essential diiron cluster, depending upon the temperature at which the diffraction data were collected. In order to extend the structural studies to the Type II methanotrophs and to determine whether one of the two known MMOH structures is generally applicable to the MMOH family, we have determined the crystal structure of the MMOH from Type II Methylosinus trichosporium OB3b (MMO OB3b) in two crystal forms to 2.0 A resolution, respectively, both determined at 18 degrees C. The crystal forms differ in that MMOB was present during crystallization of the second form. Both crystal forms, however, yielded very similar results for the structure of the MMOH. Most of the major structural features of the MMOH Bath were also maintained with high fidelity. The two irons of the active site cluster of MMOH OB3b are bridged by two OH (or one OH and one H2O), as well as both carboxylate oxygens of Glu alpha 144. This bis-mu-hydroxo-bridged "diamond core" structure, with a short Fe-Fe distance of 2.99 A, is unique for the resting state of proteins containing analogous diiron clusters, and is very similar to the structure reported for the cluster from flash frozen (-160 degrees C) crystals of MMOH Bath, suggesting a common active site structure for the soluble MMOHs. The high-resolution structure of MMOH OB3b indicates 26 consecutive amino acid sequence differences in the beta chain when compared to the previously reported sequence inferred from the cloned gene. Fifteen additional sequence differences distributed randomly over the three chains were also observed, including D alpha 209E, a ligand of one of the irons.

Amino Acid Sequence↗
PubMed1997

Permanent Dipole Moments of Methane-Type Molecules: Calculation of the DeltaJ = 0 Matrix Elements in the l = 1 Vibrational State

We examined permanent dipole moments (PDMs) of methane-type molecules induced by molecular internal motions which are expanded in terms of the vibrational coordinate operator q , total angular momentum operator J , and vibrational angular momentum operator l . The qq -, JJ -, Jl -, and ll -type quadratic terms of these operators contribute to the production of PDMs. The DeltaJ = 0 matrix elements of the four PDMs are calculated for the first excited state of the triply degenerate vibrational mode; a portion are numerically given in a table for the J </= 6 levels. We have also compared them with the PDM represented by the rotational angular momentum operator R = J - l and discussed an application of the present calculations to the v 3 = 2 state of methane.

Journal Article↗
PubMed1991

The methane monooxygenase gene cluster of Methylosinus trichosporium: cloning and sequencing of the mmoC gene.

Methane monooxygenase (MMO) is the enzyme responsible for the conversion of methane to methanol in methanotrophic bacteria. The soluble MMO enzyme complex from Methylosinus trichosporium also oxidizes a wide range of aliphatic and aromatic compounds in a number of potentially useful biotransformations. In this study we have used heterologous DNA probes from the type X methanotroph Methylococcus capsulatus (Bath) to isolate mmo genes from the type II methanotroph M. trichosporium. We report here that the gene encoding the reductase component, Protein C of MMO, lies adjacent to the genes encoding the other components of soluble MMO in M. trichosporium but is separated by an open reading frame of unknown function, orfY. The complete nucleotide sequence of these genes is presented. Sequence analysis of mmoC indicates that the N-terminus of Protein C has significant homology with 2Fe2S ferredoxins from a wide range of organisms.

Amino Acid Sequence↗
PubMed1997

Analysis of 16S rRNA and methane monooxygenase gene sequences reveals a novel group of thermotolerant and thermophilic methanotrophs, Methylocaldum gen. nov.

Two methanotrophic bacteria with optimum growth temperatures above 40 degrees C were isolated. Thermotolerant strain LK6 was isolated from agricultural soil, and the moderately thermophilic strain OR2 was isolated from the effluent of an underground hot spring. When compared to the described thermophilic methanotrophs Methylococcus capsulatus and Methylococcus thermophilus, these strains are phenotypically similar to Methylococcus thermophilus. However, their 16S rRNA gene sequences are markedly different from the sequence of Methylococcus thermophilus ( approximately 8% divergence) and, together with Methylomonas gracilis, they form a distinct, new genus within the gamma-subgroup of the Proteobacteria related to extant Type I methanotrophs. Further phenotypic characterisation showed that the isolates possess particulate methane monooxygenase (pMMO) but do not contain soluble methane monooxygenase. The nucleotide sequence of a gene encoding pMMO (pmoA) was determined for both isolates and for Methylomonas gracilis. PmoA sequence comparisons confirmed the monophyletic nature of this newly recognised group of thermophilic methanotrophs and their relationship to previously described Type I methanotrophs. We propose that strains OR2 and LK6, together with the misclassified thermophilic strains Methylomonas gracilis VKM-14LT and Methylococcus thermophilus IMV-B3122, comprise a new genus of thermophilic methanotrophs, Methylocaldum gen. nov., containing three new species: Methylocaldum szegediense, Methylocaldum tepidum and Methylocaldum gracile.

Genes, Bacterial↗
PubMed1987

Methane monooxygenase: purification and properties of flavoprotein component.

An anaerobic procedure was developed for the purification of the flavin:NADH oxidoreductase (flavoprotein) component of methane monooxygenase to homogeneity. The molecular weight of the flavoprotein determined by gel filtration was about 40,000, and by sedimentation equilibrium analysis, about 38,000. The purified flavoprotein is a monomeric protein with a sedimentation constant (S20,W) value of about 2.1 S. The absorption spectrum of the flavoprotein has a peak at 460 nm and shoulder at 395 nm. The fluorescent excitation and emission spectra of the fluorescent component of flavoprotein had peaks at 450, 370, and 530 nm, respectively. A FAD was identified as a prosthetic group of flavoprotein by thin-layer chromatography. The flavoprotein contained about 1 mol of FAD and 2 mol each of iron and acid-labile sulfide per mole of protein. The flavoprotein was directly reduced by NADH under anaerobic conditions. The formation of neutral flavin semiquinone was detected during anaerobic titration of flavoprotein by NADH and also as a free radical signal at a g value of 2.004 by EPR spectroscopy. The iron sulfur cluster has g values of 2.04, 1.96, and 1.87, yielding a g average of 1.96, characteristic of a Fe2S2 center. Antibody prepared against the flavoprotein reacted with flavoprotein and inhibited methane monooxygenase activity.

Chromatography, Gel↗
PubMed1982

Non-steroidal anti-inflammatories--XII. Mode of action of anti-inflammatory methane sulfonanilides.

The influence of anti-inflammatory methane sulfonanilides on the arachidonic acid metabolism in ram seminal vesicle homogenate depends on the pK3 of the individual substance: more acidic compounds suppress, less acidic compounds stimulate PG synthesis and enhance the PGH2/PGG2 ratio. As oxygen radicals are liberated during the conversion of PGG2 to PGH2 it is suggested that the less acidic methane sulfonanilides are scavengers of the (pro-inflammatory) oxygen radicals.

Animals↗
PubMed1992

Crystallization and preliminary X-ray analysis of the methane monooxygenase hydroxylase protein from Methylococcus capsulatus (Bath).

Methane monooxygenase is a multicomponent enzyme system that catalyzes the conversion of methane to methanol in methanotrophic bacteria. Catalysis occurs at non-heme dinuclear iron centers contained in the hydroxylase component of the system, a dimer of composition alpha 2 beta 2 gamma 2. The hydroxylase protein from Methylococcus capsulatus (Bath) has been crystallized from aqueous solutions containing polyethylene glycol, lithium sulfate, and ammonium acetate. The crystals are orthorhombic, space group P2(1)2(1)2(1), with one dimer of relative molecular mass M(r) = 252,000 in the asymmetric unit. The unit cell dimensions are a = 62.6 A, b = 110.1 A, c = 333.5 A. The crystals diffract uniformly beyond 2.5 A resolution. Crystals of the related hydroxylase from Methylosinus trichosporium OB3b have also been obtained.

Crystallization↗
PubMed1988

Spectroscopic properties of the hydroxylase of methane monooxygenase.

The hydroxylase component of methane monooxygenase (EC 1.14.13.25), which catalyzes the oxidation of methane to methanol, has been studied by visible, electron spin resonance and X-ray spectroscopies. The enzyme appears to possess a mu-oxo- or mu-hydroxo-bridged binuclear iron site, with no sulfur ligands to the cluster. Each Fe has 4-6 oxygen (or nitrogen) ligands, at an average distance of 1.92 +/- 0.03 A. The Fe-Fe distance is 3.05 +/- 0.05 A. Essentially all of the irons are in the Fe3+ state as the enzyme is prepared, but reduction with N-methylphenazonium methosulfate generates ESR-detectable states that appear to emanate from mixed-valence binuclear sites. One of these, with gav near 1.85, displays typical Curie law microwave saturation behavior, but the other, gav near 1.73, has a very potent method of spin-relaxation. Together they account for approximately 0.6 spins per molecule.

Binding Sites↗
PubMed1995

Increased axonal regrowth of lesioned rat sciatic nerve by veratrylguanidine methane sulfonate.

Neurotrophic factors appear as essential factors for normal development and repair of the nervous tissue. Veratrylguanidine methane sulfonate, has been shown to induce important neurite outgrowth of cultured dorsal root ganglia isolated from newborn rats. Its action was similar to that of NGF and was found to be additive to that of NGF. In order to see if this compound was able to stimulate axonal growth in adult animals, we examined the effect of this substance on the regeneration of the lesioned sciatic nerve. Using histochemical, immunohistochemical and ultrastructural studies, it is shown that a single intraperitoneal injection of veratrylguanidine methane sulfonate significantly increases the axonal growth during repair of the adult rat sciatic nerve. The efficiency of this substance is explained by its good targeting and long life time in the sciatic nerve.

Animals↗
PubMed1994

Chemical modification of the hydroxylase of soluble methane monooxygenase gives one form of the protein with significantly increased thermostability and another that functions well in organic solvents.

Proteolysis of the hydroxylase component of soluble methane monooxygenase (MMO) with trypsin yielded a protein which retained 50% activity in a standard MMO assay. In an H2O2-driven assay, in which H2O2 replaced two of the protein components, NADH and O2 used in the standard assay, the proteolysed hydroxylase retained full activity for ethane, propane and propene, but had a 2-3-fold increase with methane as substrate. Several crosslinking reagents have been tested for their ability to stabilise the proteolysed form of the hydroxylase. Using polyoxyethylene bis(imidazolyl carbonyl) (M(r) 3350) as the crosslinking agent, increased thermostability of the hydroxylase was observed. Activated methoxypolyethylene glycol (M(r) 5000) was used to modify the hydroxylase which was now soluble in organic solvents as well as water and could be activated by H2O2. The glycol-modified hydroxylase functioned well in organic solvents in the catalysis of propene oxidation.

Enzyme Stability↗
PubMed1984

Paper pulpmill sludge utilization: techno-economic potential for fuel ethanol, methane and scp production.

Various processes have been developed or proposed for converting cellulosic residues from pulp and paper mills into products which can be used for fuel or food. Among the promising practical possibilities are processes for ethanol, methane and microbial protein production by fermentation technology. Given the current Canadian financial climate and product demand, the results of techno-economic sensitivity analyses of these three process options indicate that microbial protein production for animal food applications is the most attractive followed by methane then ethanol, the last being quite uneconomical at present. Ironically, research emphasis seems to be placed in the reverse order. It is evident that the relevant costs of upstream and downstream processing in the various process proposals have not been adequately addressed. Case studies of several scenarios illustrate the problems.

Journal Article↗