Formaldehyde oxidation and methanogenesis

Formaldehyde oxidation by cell-free extracts of Methanobacterium thermoautotrophicum was shown to drive methanogenesis from CH3-S-coenzyme M or HCHO under a nonreductive atmosphere of N2. Under N2 when HCHO was the sole source of carbon and reducing equivalents in the reaction, it underwent oxidation and reduction events (disproportionation), the sum of the reactions being 3 HCHO + H2O----CH4 + 2 HCOO - + 2H+. This reaction predicts a CH4/HCHO ratio of 1/3, which is in agreement with the experimental finding of 1/2.9. In extracts of the mesophilic methanogen Methanococcus voltae and the extreme thermophile Methanococcus jannaschii , which exhibited formate dehydrogenase activity, the CH4/HCHO ratio was 1/2. NADPH stimulated methane formation from HCHO under N2. An unidentified, oxygen-labile cofactor, the formaldehyde activation factor, present in boiled-cell extract was discovered. Methanopterin , an oxygen-stable molecule, also substituted for boiled-cell extract.     

Increased NADH-dependent production of reactive oxygen intermediates by microsomes after chronic ethanol consumption: comparisons with NADPH.

Microsomes from chronic ethanol-fed rats were previously shown to catalyze the NADPH-dependent production of reactive oxygen intermediates at elevated rates compared to controls. Recent studies have shown that NADH can also serve as a reductant and promote the production of oxygen radicals by microsomes. The current study evaluated the influence of chronic ethanol consumption on NADH-dependent microsomal production of reactive oxygen intermediates, and compared the results with NADH to those of NADPH. Microsomal oxidation of chemical scavengers, taken as a reflection of the production of hydroxyl radical (.OH)-like species was increased about 50% with NADH as cofactor and about 100% with NADPH after chronic ethanol consumption. The potent inhibition of the production of .OH-like species by catalase suggests a precursor role for H2O2 in .OH production. Rates of NADH- and NADPH-dependent H2O2 production were increased by about 50 and 70%, respectively, after chronic ethanol consumption. A close correlation between rates of H2O2 production and generation of .OH-like species was observed for both NADH and NADPH, and increased rates of H2O2 production appear to play an important role in the elevated generation of .OH-like species after chronic ethanol treatment. Microsomal lipid peroxidation was elevated about 60% with NADH, and 120% with NADPH, after ethanol feeding. With both types of microsomal preparations, the characteristics of the NADH-dependent reactions were similar to the NADPH-dependent reactions, e.g., sensitivity to antioxidants and free radical scavengers and catalytic effectiveness of ferric complexes. However, rates with NADPH exceeded the NADH-dependent rates by 50 to 100%, and the increased production of reactive oxygen intermediates by microsomes after ethanol treatment was greater with NADPH (about twofold) than with NADH (about 50%). Oxidation of ethanol results in an increase in hepatic NADH levels and interaction of NADH, iron, and microsomes can produce potent oxidants capable of initiating lipid peroxidation and oxidizing .OH scavengers. These acute metabolic interactions produced by ethanol-derived NADH are increased, not attenuated, in microsomes from chronic ethanol-fed rats, and it is possible that such increases in NADH (and NADPH)-dependent production of reactive oxygen species play a role in the development of oxidative stress in the liver as a consequence of ethanol treatment.     

NADH-dependent microsomal interaction with ferric complexes and production of reactive oxygen intermediates

The interaction of NADPH with ferric complexes to catalyze microsomal generation of reactive oxygen intermediates has been well studied. Experiments were carried out to characterize the ability of NADH to interact with various ferric chelates to promote microsomal lipid peroxidation and generation of .OH-like species. In the presence of NADH and iron, microsomes produced .OH as assessed by the oxidation of a variety of .OH scavenging agents. Rates of NADH-dependent .OH production were 50 to 80% those of the NADPH-catalyzed reaction. The oxidation of dimethyl sulfoxide or t-butyl alcohol was inhibited by catalase and competitive .OH scavengers but not by superoxide dismutase or carbon monoxide. NADH-dependent .OH production was effectively catalyzed by ferric-EDTA and ferric-diethylenetriaminepentaacetic acid (DTPA), whereas ferric-ATP and ferric-citrate were poor catalysts. All these ferric chelates were reduced by microsomes in the presence of NADH (and NADPH). H2O2 was produced in the presence of NADH in a reaction stimulated by the addition of ferric-EDTA, consistent with the increase in .OH production. The latter appeared to be limited by the rate of H2O2 generation rather than the rate of reduction of the ferric chelate. NADH-dependent lipid peroxidation was much lower than the NADPH-catalyzed reaction and showed an opposite response to catalysis by ferric complexes compared to .OH generation as production of thiobarbituric acid-reactive material was increased with ferric-ATP and -citrate, but not with ferric-EDTA or- DTPA, and was not affected by catalase, SOD, or .OH scavengers. These results indicate that NADH can support microsomal reduction of ferric chelates, with the subsequent production of .OH-like species and peroxidation of lipids. The pattern of response of the NADH-dependent reactions with respect to catalytic effectiveness of ferric chelates and sensitivity to radical scavengers is similar to that found with NADPH. Many of the metabolic actions of ethanol have been ascribed to production of NADH as a consequence of oxidation by alcohol dehydrogenase. Since the cytosol normally maintains a highly oxidized NAD+/NADH redox ratio, it is interesting to speculate that increased availability of NADH from the oxidation of ethanol may support microsomal reduction of iron complexes, with the subsequent generation of reactive oxygen intermediates.     

Redox reactions in apoplast of growing cells

Redox reactions affecting the cell wall extensibility proceed in the apoplast of growing cells. The reactions involve dozens of oxidoreductases localized in cell walls (Class I and III heme peroxidases, FAD- and Cu-dependent amine oxidases, oxalate oxidase, ascorbate oxidase, superoxide dismutase, etc.) together with NADPH oxidase and quinone reductase of the plasma membrane. The cell wall extensibility decreases due to peroxidase-catalyzed phenolic cross-links of polymers. Cell growth is proven to be directly dependent on production of reactive oxygen species (ROS) in the apoplast. A special value is attached to hydroxyl radical OH?, which is able to locally cleave polysaccharides and, thus, increase wall extensibility. Generation of OH? results from one-electron reduction of H₂O₂ and, consequently, is related to the complex of enzymatic and spontaneous reactions of H₂O₂ turnover in the apoplast. The extensibility also depends on an ascorbate concentration in the apoplast and on a ratio of its oxidized to reduced forms. This dependence is expressed not only in the well-known down-regulation of phenols oxidation but also through pro-oxidant and signal activities. There is only indirect evidence of a role of apoplast-originated redox signaling in the cell growth regulation. In addition to ascorbate, the signaling may supposedly involve ROS, glutathione recycling reactions, numerous redox-sensitive peptides, and proteins localized in the cell wall and the plasma membrane.     

Induced pluripotent stem cell‐conditional medium inhibits H9C2 cardiomyocytes apoptosis via autophagy flux and Wnt/β‐catenin pathway

Induced pluripotent stem cell‐derived conditioned medium (iPS‐CM) could improve cell viability in many types of cells and may be a better alternative for the treatment of myocardial infarction. This study aimed to examine the influence of iPS‐CM on anti‐apoptosis and the proliferation of H9C2 cardiomyocytes and investigate the underlying mechanisms. H9C2 cardiomyocytes were exposed to 200 μmol/L hydrogen peroxide (H₂O₂) for 24 hours with or without pre‐treatment with iPS‐CM. The ratio of apoptotic cells, the loss of mitochondrial membrane potential (△Ψm) and the levels of intracellular reactive oxygen species were analysed by flow cytometric analysis. The expression levels of BCL‐2 and BAX proteins were analysed by Western blot. Cell proliferation was assessed using cell cycle and EdU staining assays. To study cell senescence, senescence‐associated β‐galactosidase (SA‐β‐gal) staining was conducted. The levels of malondialdehyde, superoxide dismutase and glutathione were also quantified using commercially available enzymatic kits. The results showed that iPS‐CM containing basic fibroblast growth factor significantly reduced H₂O₂‐induced H9C2 cardiomyocyte apoptosis by activating the autophagy flux pathway, promoted cardiomyocyte proliferation by up‐regulating the Wnt/β‐catenin pathway and inhibited oxidative stress and cell senescence. In conclusion, iPS‐CM effectively enhanced the cell viability of H9C2 cardiomyocytes and could potentially be used to inhibit cardiomyocytes apoptosis to treat myocardial infarction in the future.     

Is *OH the active Fenton intermediate in the oxidation of ethanol?

A re-examination of the data of Rush and Koppenol (J. Inorg. Biochem. 29 (1987) 199) on the competitive oxidation of C2H5OH and Fe2+ by Fenton's reagent shows that the ratio of the rate constants of the two reactions is 3.2 and not 6.3. The significance of this finding is that it is not possible to identify the active intermediate in the Fenton reaction with the *OH radical.     

Long‐term ammonium nutrition of Arabidopsis increases the extrachloroplastic NAD(P)H/NAD(P)+ ratio and mitochondrial reactive oxygen species level in leaves but does not impair photosynthetic capacity

Ammonium nutrition has been suggested to be associated with alterations in the oxidation‐reduction state of leaf cells. Herein, we show that ammonium nutrition in Arabidopsis thaliana increases leaf NAD(P)H/NAD(P)⁺ ratio, reactive oxygen species content and accumulation of biomolecules oxidized by free radicals. We used the method of rapid fractionation of protoplasts to analyse which cellular compartments were over‐reduced under ammonium supply and revealed that observed changes in NAD(P)H/NAD(P)⁺ ratio involved only the extrachloroplastic fraction. We also showed that ammonium nutrition changes mitochondrial electron transport chain activity, increasing mitochondrial reactive oxygen species production. Our results indicate that the functional impairment associated with ammonium nutrition is mainly associated with redox reactions outside the chloroplast.     

Stimulation of arachidonic acid metabolism in primary cultures of osteoblast-like cells by hormones and drugs

The effects of parathyroid hormone (PTH), dihydroxycholecalciferol (1,25-(OH)₂ D₃), thrombin, epidermal growth factor (EGF) and 12-o-tetradecanoylphorbol-13-acetate (PMA) on the biosynthesis and release of arachidonic acid metabolites were studied in primary cultures of osteoblast-like cells isolated from 18-day-old chick embryo calvaria. Cells were labelled with (¹⁴C)-arachidonic acid for 30 h. The radioactive eicosanoids were extracted from the cell culture media after a further 30 h stimulation period and analysed on a PRP-1 column by HPLC. The radioactive products were characterized by co-elution of (³H) standard prostanoids. Osteoblasts showed a basal release of the prostanoids 6-keto-PGF_1α, TXB₂, PGF_2α, PGE₂, PGD₂ and PGB₂, the latter being the most abundant one. Indomethacin (10⁻⁵ M) effectively inhibited the basal release, but not that of an as yet unidentified compound. The release of prostanoids was stimulated by PTH (2 U/ml), thrombin (0.4 NIH/ml), EGF (50 ng/ml) and PMA (25 ng/ml), the latter being by far the most potent one. 1,25-(OH)₂D₃ was found to slightly inhibit the prostanoid release. These results indicate: (1) primary cultures of osteoblasts synthesize several prostaglandins, thromboxane B₂ and one unidentified product. (2) the action on bone of PTH and the various drugs tested may be, at least partly, mediated by an increased prostaglandin production by osteoblasts. Clearly this does not apply to 1,25-(OH)₂D₃.     

The tryptophan synthase alpha 2 beta 2 complex: a comparison of the reactivity of amino groups in the alpha and beta 2 subunits and in the complex by differential labeling studies

The interaction of the alpha and beta 2 subunits of tryptophan synthase of Escherichia coli to form an alpha 2 beta 2 complex has been probed by differential labeling studies. In the first step the separate alpha or beta 2 subunit or the alpha 2 beta 2 complex was labeled by reductive methylation with trace amounts of [3H]HCHO in the presence of NaCNBH3. In the second step the 3H-labeled preparation was fully labeled under denaturing conditions with [14C]HCHO and NaCNBH3. Peptides containing labeled monomethyl or dimethyl amino groups were isolated after thermolytic digestion or after cyanogen bromide treatment. The 3H/14C ratio of each peptide is a measure of the relative reactivity of the amino group or groups in each peptide. The most reactive amino group in the alpha subunit, lysine-109, is strongly shielded from modification in the alpha 2 beta 2 complex. The most reactive amino group in the beta 2 subunit, the amino-terminal threonine, is not shielded from modification in the alpha 2 beta 2 complex.     

In vivo enzymology: 13C NMR measurement of a kinetic isotope effect for methanol oxidation in Methylosinus trichosporium OB3b

The competitive oxidation of ¹³CH₃OH and ¹³CD₃OH has been observed using in vivo ¹³C NMR spectroscopy. Simultaneous ¹H and ²H decoupling gave isotopically shifted ¹³C singlets for the two methanol isotopomers. The measured enzymic isotope effect, kH/kD is approx. 1.8, indicating that CH bond cleavage is not rate-determining.     

Metabolic mechanisms of methanol/formaldehyde in isolated rat hepatocytes: carbonyl-metabolizing enzymes versus oxidative stress

Methanol (CH(3)OH), a common industrial solvent, is metabolized to toxic compounds by several enzymatic as well as free radical pathways. Identifying which process best enhances or prevents CH(3)OH-induced cytotoxicity could provide insight into the molecular basis for acute CH(3)OH-induced hepatoxicity. Metabolic pathways studied include those found in 1) an isolated hepatocyte system and 2) cell-free systems. Accelerated Cytotoxicity Mechanism Screening (ACMS) techniques demonstrated that CH(3)OH had little toxicity towards rat hepatocytes in 95% O(2), even at 2M concentration, whereas 50 mM was the estimated LC(50) (2h) in 1% O(2), estimated to be the physiological concentration in the centrilobular region of the liver and also the target region for ethanol toxicity. Cytotoxicity was attributed to increased NADH levels caused by CH(3)OH metabolism, catalyzed by ADH1, resulting in reductive stress, which reduced and released ferrous iron from Ferritin causing oxygen activation. A similar cytotoxic mechanism at 1% O(2) was previous found for ethanol. With 95% O(2), the addition of Fe(II)/H(2)O(2), at non-toxic concentrations were the most effective agents for increasing hepatocyte toxicity induced by 1M CH(3)OH, with a 3-fold increase in cytotoxicity and ROS formation. Iron chelators, desferoxamine, and NADH oxidizers and ATP generators, e.g. fructose, also protected hepatocytes and decreased ROS formation and cytotoxicity. Hepatocyte protein carbonylation induced by formaldehyde (HCHO) formation was also increased about 4-fold, when CH(3)OH was oxidized by the Fenton-like system, Fe(II)/H(2)O(2), and correlated with increased cytotoxicity. In a cell-free bovine serum albumin system, Fe(II)/H(2)O(2) also increased CH(3)OH oxidation as well as HCHO protein carbonylation. Nontoxic ferrous iron and a H(2)O(2) generating system increased HCHO-induced cytotoxicity and hepatocyte protein carbonylation. In addition, HCHO cytotoxicity was markedly increased by ADH1 and ALDH2 inhibitors or GSH-depleted hepatocytes. Increased HCHO concentration levels correlated with increased HCHO-induced protein carbonylation in hepatocytes. These results suggest that CH(3)OH at 1% O(2) involves activation of the Fenton system to form HCHO. However, at higher O(2) levels, radicals generated through Fe(II)/H(2)O(2) can oxidize CH(3)OH/HCHO to form pro-oxidant radicals and lead to increased oxidative stress through protein carbonylation and ROS formation which ultimately causes cell death.     

Oxidation of Methanol,Formaldehyde and Formate by a Candida Species

1. The oxidation of methanol to carbon dioxide by Candida N–16 grown on methanol was investigated. The presence of enzymes which catalyze the following reaction was found in the cell-free extract of the yeast employed; CH₃OH→HCHO→HCOOH→CO₂. 2. Methanol was oxidized to formaldehyde by an alcohol oxidase. The reaction was as follows; CH₃OH+O₂→HCHO+H₂O₂. The alcohol oxidase was crystallized after purification by ammonium sulfate-precipitation and column chromatography using DEAE-Sephadex A-50. A prosthetic group of the enzyme was proved to be FAD. The enzyme possessed a broad specificity for alcohols such as methanol, ethanol, n-propanol, n-butanol and n-amylalcohol. The enzyme was inducibly formed only by the addition of methanol. 3. The oxidation of formaldehyde to formate was catalyzed by a NAD-linked dehydrogenase dependent on GSH. 4. Formate was oxidized by a NAD-linked dehydrogenase. 5. Catalase was also found in the extract, and methanol was chemically oxidized by the reaction of catalase and hydrogen peroxide which was generated by the alcohol oxidase system. 6. The oxidation pathway from methanol to carbon dioxide was also found in other methanol-utilizing yeasts such as Candida N-17, Saccharomyces H-1 and Torulopsis M-1.     

Oxidative degradation of quinazoline in supercritical water: a combined ReaxFF and DFT study

ABSTRACT

Quinazoline (Qu) is a representative heterocyclic compound in chemical wastewater. In this work, the supercritical water oxidation of Qu is investigated using molecular dynamics simulations based on the ReaxFF reactive force field combined with density functional theory (DFT) method. The detailed reaction pathways, transformation routes of nitrogen element, and kinetic behaviours are systematically analyzed at the atomistic level. Simulation results show that the increment of temperature and O₂ molecule accelerates the reaction rate and facilitates the complete destruction of Qu. The pyrimidine ring in Qu can be attacked by the OH radical, O₂ molecule, and H₂O molecule, thereby causing three main pathways for the pyrimidine ring-opening reaction. The aromatic ring undergoes a ring rearrangement process and opens under the attack of active O₂ molecules. DFT calculations demonstrate that the supercritical water cluster can decrease the cracking energy of chemical bonds and accelerate the degradation rate of Qu. In addition, the transformation routes of nitrogen element during reaction are described. NH₃ is found to be the primary N-containing product after ring-opening reactions and is an intermediate for the production of N₂. Finally, the value of activation energy is obtained as 123.0?kJ/mol, which is reasonably consistent with the experimental results.     

Histochemical Comparison of the Casella,Bauer, and Periodic Acid Oxidation-Schiff Leucofuchsin Technics

Chromic acid, potassium permanganate and periodic acid apparently produce aldehyde from the same general group of substances. Chromic acid and potassium permanganate also destroy the aldehyde which they have produced, as well as that previously produced by periodic acid oxidation and by the Feulgen hydrochloric acid hydrolysis. Sulfite blockade, by occupying a considerable proportion of the aldehyde groups produced by periodic acid oxidation, creates a Schiff reaction similar to that produced by primary or secondary chromic acid or permanganate oxidation.

It is suggested that the periodic acid Schiff positive substances which fail to give distinct Bauer and Casella reactions, are those with relatively few reactive 1,2 glycol, 1,2 OH,NH₂, or 1,2 OH,NHR groupings per molecule.     

Effects of Nitrapyrin [2-Chloro-6-(Trichloromethyl) Pyridine] on the Obligate Methanotroph Methylosinus trichosporium OB3b

Nitrapyrin inhibited growth, CH₄ oxidation, and NH₄⁺ oxidation, but not the oxidation of CH₃OH, HCHO, or HCOONa, by Methylosinus trichosporium OB3b, suggesting that nitrapyrin acts against the methane monooxygenase enzyme system. The inhibition of CH₄ oxidation could be reversed by repeated washing of nitrapyrin-inhibited cells, indicating that its effect is bacteriostatic. The addition of Cu²⁺ did not release the inhibition. Methane oxidation was also inhibited by 6-chloro-2-picoline. These data suggest that the mode of action of nitrapyrin on M. trichosporium is different from that on chemoautotrophic NH₄⁺ oxidizers or methanogens.     

New assay method based on Raman spectroscopy for enzymes reacting with gaseous substrates

Enzyme activity is typically assayed by quantitatively measuring the initial and final concentrations of the substrates and/or products over a defined time period. For enzymatic reactions involving gaseous substrates, the substrate concentrations can be estimated either directly by gas chromatography or mass spectrometry, or indirectly by absorption spectroscopy, if the catalytic reactions involve electron transfer with electron mediators that exhibit redox‐dependent spectral changes. We have developed a new assay system for measuring the time course of enzymatic reactions involving gaseous substrates based on Raman spectroscopy. This system permits continuous monitoring of the gas composition in the reaction cuvette in a non‐invasive manner over a prolonged time period. We have applied this system to the kinetic study of the [NiFe] hydrogenase from Desulfovibrio vulgaris Miyazaki F. This enzyme physiologically catalyzes the reversible oxidation of H₂ and also possesses the nonphysiological functions of H/D exchange and nuclear spin isomer conversion reactions. The proposed system has the additional advantage of enabling us to measure all of the hydrogenase‐mediated reactions simultaneously. Using the proposed system, we confirmed that H₂ (the fully exchanged product) is concomitantly produced alongside HD by the H/D exchange reaction in the D₂/H₂O system. Based on a kinetic model, the ratio of the rate constants of the H/D exchange reaction (k) at the active site and product release rate (k_out) was estimated to be 1.9 ± 0.2. The proposed assay method based on Raman spectroscopy can be applied to the investigation of other enzymes involving gaseous substrates.     

Azotobacter vinelandii vanadium nitrogenase: formaldehyde is a product of catalyzed HCN reduction, and excess ammonia arises directly from catalyzed azide reduction

The Mo-nitrogenase-catalyzed reduction of both cyanide and azide results in the production of excess NH3, which is an amount of NH3 over and above that expected to be formed from the well-recognized reactions. Several suggestions about the possible sources of excess NH3 have been made, but previous attempts to characterize these reactions have met with either limited (or no) success or controversy. Because V-nitrogenase has a propensity to release partially reduced intermediates, e.g., N2H4 during N2 reduction, it was selected to probe the reduction of cyanide and azide. Sensitive assay procedures were developed and employed to monitor the production of either HCHO or CH3OH (its further two-electron-reduced product) from HCN. Like Mo-nitrogenase, V-nitrogenase suffered electron-flux inhibition by CN- (but was much less sensitive than Mo-nitrogenase), but unlike the case for Mo-nitrogenase, MgATP hydrolysis was also inhibited by CN-. V-Nitrogenase also released more of the four-electron-reduced intermediate, CH3NH2, than did Mo-nitrogenase. At high NaCN concentrations, V-nitrogenase directed a significant percentage of electron flux into excess NH3, and under these conditions, substantial amounts of HCHO, but no CH3OH, were detected for the first time. With azide, in contrast to the case for Mo-nitrogenase, both total electron flux and MgATP hydrolysis with V-nitrogenase were inhibited. V-Nitrogenase, unlike Mo-nitrogenase, showed no preference between the two-electron reduction to N2-plus-NH3 and the six-electron reduction to N2H4-plus-NH3. V-Nitrogenase formed more excess NH3, but reduction of the N2 produced by the two-electron reduction of N3(-) was not its source. Rather, it was formed directly by the eight-electron reduction of N3(-). Unlike Mo-nitrogenase, CO could not completely eliminate either cyanide or azide reduction by V-nitrogenase. CO did, however, eliminate the inhibition of both electron flux and MgATP hydrolysis by CN-, but not that caused by azide. These different responses to CO suggest different sites or modes of interaction for these two substrates with V-nitrogenase.     

Decomposition of toluene in a steady-state atmospheric-pressure glow discharge

Results are presented from experimental studies of decomposition of toluene (C₆H₅CH₃) in a polluted air flow by means of a steady-state atmospheric pressure glow discharge at different water vapor contents in the working gas. The experimental results on the degree of C₆H₅CH₃ removal are compared with the results of computer simulations conducted in the framework of the developed kinetic model of plasma chemical decomposition of toluene in the N₂: O₂: H₂O gas mixture. A substantial influence of the gas flow humidity on toluene decomposition in the atmospheric pressure glow discharge is demonstrated. The main mechanisms of the influence of humidity on C₆H₅CH₃ decomposition are determined. The existence of two stages in the process of toluene removal, which differ in their duration and the intensity of plasma chemical decomposition of C₆H₅CH₃ is established. Based on the results of computer simulations, the composition of the products of plasma chemical reactions at the output of the reactor is analyzed as a function of the specific energy deposition and gas flow humidity. The existence of a catalytic cycle in which hydroxyl radical OH acts a catalyst and which substantially accelerates the recombination of oxygen atoms and suppression of ozone generation when the plasma-forming gas contains water vapor is established.     

Measurement of products from X-irradiated glycylglycine in oxygen-free aqueous solutions.

The product yields in X-irradiated aqueous solutions of glycylglycine (0.05 M and 1.0 M) were measured under deoxygenated conditions. Comparison was made between the results obtained from X- and 60Co gamma-irradiated glycylglycine solutions reported by Garrison, Sokol, and Bennett-Corniea (Radiat. Res. 53, 376-384, 1973). The mechanisms proposed by Garrison et al. were tested by evaluating the stoichiometric relationships. The two intermediate radicals, deamination and H-abstraction radicals, were produced in the initial interactions of glycylglycine with reactive species (e-aq, OH, H) formed in H2O. Although the difference was fairly large at 0.05 M, the production of deamination radicals agreed well with the consumption of the radicals at 1.0 M. The production and the consumption of H-abstraction radicals were within the estimated experimental error in dilute solutions. Among all the products only the G value of aspartic acid decreased with increasing concentration of glycylglycine. This could be attributed to the fact that more acetylglycine is formed at the expense of aspartic acid at 1.0 M than at 0.05 M glycylglycine solutions. Competitive reactions involved with deamination radicals under conditions of homogeneously distributed reactants are discussed to elucidate the radiation chemistry of glycylglycine.     

Biotransformation of benzene and toluene to catechols by phenol hydroxylase from Arthrobacter sp. W1

Phenol hydroxylase gene engineered microorganism (PH_IND) was used to synthesize catechols from benzene and toluene by successive hydroxylation reaction. HPLC-MS and ¹H NMR analysis proved that the products of biotransformation were the corresponding catechols via the intermediate production of phenols. It was indicated that the main products of toluene oxidation were o-cresol and p-cresol. 3-Methylcatechol was the predominant product for m-cresol biotransformation. Formation rate of catechol (25 μM/min/g cell dry weight) was 1.43-fold higher than that of methylcatechols. It was suggested that phenol hydroxylase could be successfully used to transform both benzene and toluene to catechols by successive hydroxylation.