scholarly journals Reaction of caa3-type terminal cytochrome oxidase from the thermophilic bacterium PS3 with oxygen and carbon monoxide at low temperatures

1984 ◽  
Vol 221 (2) ◽  
pp. 529-533 ◽  
Author(s):  
N Sone ◽  
A Naqui ◽  
C Kumar ◽  
B Chance
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Cytochrome Oxidase ◽  
Low Temperatures ◽  
Thermophilic Bacterium ◽  
Reduced Form ◽  
Compound A ◽  
First Order ◽  
First Order Kinetics ◽  
Higher Temperature

Reaction of O2 and CO with a caa3-type terminal cytochrome oxidase (EC 1.9.3.1) from the thermophilic bacterium PS3 grown with high aeration was studied at low temperatures. The CO recombination at the temperature range studied (−50 degrees C to −80 degrees C) followed first-order kinetics with an activation energy of 29.3 kJ/mol (7.0 kcal/mol). In the presence of O2 at −113 degrees C the photolysed reduced form binds O2 to form an ‘oxy’ intermediate similar to Compound A. At a higher temperature (-97 degrees C) another intermediate, similar to Compound B, is formed as a result of electron transfer from the enzyme to the liganded O2.

Methanation on exfoliated and supported MoS2

1989 ◽  
Vol 67 (5) ◽  
pp. 862-866 ◽  
Author(s):  
Guenter A. Scholz ◽  
S. Roy Morrison
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Transition Metal Catalysts ◽  
Surface Species ◽  
Reaction Products ◽  
Third Order ◽  
Ammonium Heptamolybdate ◽  
First Order ◽  
Methanation Reaction ◽  
Improved Performance

The methanation reaction on MoS2 exfoliated to a thickness of a few layers or less and adsorbed onto alumina is found to be very small. However, by calcining and resulfiding the exfoliated MoS2 catalysts, greatly improved performance is achieved that is at least equal to the commercial catalysts based on ammonium heptamolybdate. The creation of molybdenum oxysulflde surface species therefore appears to be a necessary step toward producing significant methanation rates with exfoliated and supported MoS2. The methanation products are almost exclusively CO2 and CH4, their mole ratios near unity, with otherwise only very much smaller amounts of longer chain hydrocarbons. The activation energy for methanation is generally observed to be near 100 kJ/mol, with the overall reaction being first order in the carbon monoxide concentration and third order in the hydrogen concentration. In contrast to the transition-metal catalysts, no water could be detected in the reaction products of the molybdenum based catalyst. Keywords: methanation reaction on MoS2, exfoliated and supported MoS2 as catalyst.

scholarly journals The reaction of cytochrome oxidase with oxygen in the fission yeast Schizosaccharomyces pombe 972h-. Studies at subzero temperatures and measurement of apparent oxygen affinity

1979 ◽  
Vol 184 (3) ◽  
pp. 555-563 ◽  
Author(s):  
R K Poole ◽  
D Lloyd ◽  
B Chance
Keyword(s):  
Schizosaccharomyces Pombe ◽  
Fission Yeast ◽  
Cytochrome Oxidase ◽  
Flash Photolysis ◽  
Oxygen Affinity ◽  
Intermediate Compound ◽  
Reduced Form ◽  
Difference Spectra ◽  
Intact Cells ◽  
Compound A

1. Cytochrome alpha 3 in whole-cell suspensions of the fission yeast Schizosaccharomyces pombe reacted in the reduced form with CO to give a photodissociable CO complex with absorption maxima at 429, 543 and 591 nm in CO-liganded reduced-minus-reduced difference spectra. 2. Other CO-bound haemoproteins, cytochromes P-420 and P-450, were not photodissociated under the conditions employed. 3. Measurements of the rates of reassociation of CO with cytochrome alpha 3 after flash photolysis over the temperature range from −101 to −109 degrees C gave a value for Eact. of 28.6 kJ/mol. 4. Between −94 and −106 degrees C, O2 reacted with cytochrome oxidase in intact cells to give an oxygenated intermediate (compound A). 5. At −70 degrees C compound A was converted into a second spectrally distinct intermediate (compound B). 6. Electron transport, indicated by the oxidation of cytochromes alpha + alpha 3 and cytochrome c, did not occur until the temperature was raised to −50 degrees C. 7. At room temperature cytochfome oxidase was oxidized to 50% of its steady-state concentration by 0.35 microM-O2.

Effect of thiol oxidation and thiol export from erythrocytes on determination of redox status of homocysteine and other thiols in plasma from healthy subjects and patients with cerebral infarction

1995 ◽  
Vol 41 (3) ◽  
pp. 361-366 ◽  
Author(s):  
A Andersson ◽  
A Lindgren ◽  
B Hultberg
Keyword(s):  
Cerebral Infarction ◽  
Healthy Subjects ◽  
Redox Status ◽  
Reduced Form ◽  
Temperature Dependent ◽  
First Order ◽  
First Order Kinetics ◽  
Before And After ◽  
Reduced Forms

Abstract Changes in concentration of reduced and oxidized low-M(r) thiols were measured in blood and plasma before and after the separation of blood cells. If centrifugation of blood was postponed, the reduced form of homocysteine in plasma increased with time at 22 degrees C; in contrast, the concentrations of other reduced thiols (cysteine, glutathione, and cysteinylglycine) decreased. In plasma the reduced forms of all thiols disappeared at a rate that followed first-order kinetics. The rates of disappearance ("half-lives") were temperature-dependent; they were about the same for glutathione and homocysteine (11.7 and 14.3 min, respectively, at 22 degrees C) and somewhat higher for cysteinylglycine and cysteine. After establishing proper sampling conditions for reduced thiols, we measured this thiol fraction as well as free (non-protein-bound) and total thiols in 10 reference subjects and 19 patients with cerebral infarction. Mild but significant hyperhomocysteinemia involving total and free homocysteine (but not reduced homocysteine) was found in the patients.

THE THERMAL DECOMPOSITION OF HYDROGEN PEROXIDE VAPOUR. II.

1947 ◽  
Vol 25b (2) ◽  
pp. 135-150 ◽  
Author(s):  
Paul A. Giguère
Keyword(s):  
Activation Energy ◽  
Hydrogen Peroxide ◽  
Thermal Decomposition ◽  
Low Temperatures ◽  
Hydrocyanic Acid ◽  
Quartz Surface ◽  
First Order ◽  
Acid Washing ◽  
Reaction Vessels ◽  
Low Pressures

The decomposition of hydrogen peroxide vapour has been investigated at low pressures (5 to 6 mm.) in the temperature range 50° to 420 °C., for the purpose of determining the effect of the nature and treatment of the active surfaces. The reaction was followed in an all-glass apparatus and, except in one case, with one-litre round flasks as reaction vessels. Soft glass, Pyrex, quartz, and metallized surfaces variously treated were used. In most cases the decomposition was found to be mainly of the first order but the rates varied markedly from one vessel to another, even with vessels made of the same type of glass. On a quartz surface the decomposition was preceded by an induction period at low temperatures. Fusing the glass vessels slowed the reaction considerably and increased its apparent activation energy; this effect was destroyed by acid washing. Attempts to poison the surface with hydrocyanic acid gave no noticeable result. The marked importance of surface effects at all temperatures is considered as an indication that the reaction was predominantly heterogeneous under the prevailing conditions. Values ranging from 8 to 20 kcal. were found for the apparent energy of activation. It is concluded that the decomposition of hydrogen peroxide vapour is not very specific as far as the nature of the catalyst is concerned.

THE KINETICS OF CUPRENE GROWTH

1950 ◽  
Vol 28b (7) ◽  
pp. 358-372
Author(s):  
Cyrias Ouellet ◽  
Adrien E. Léger
Keyword(s):  
Nitric Oxide ◽  
Activation Energy ◽  
Carbon Monoxide ◽  
Apparent Activation Energy ◽  
Copper Catalyst ◽  
Maximum Velocity ◽  
Static System ◽  
Reaction Velocity ◽  
First Order ◽  
Kinetics Of

The kinetics of the polymerization of acetylene to cuprene on a copper catalyst between 200° and 300 °C. have been studied manometrically in a static system. The maximum velocity of the autocatalytic reaction shows a first-order dependence upon acetylene pressure. The reaction is retarded in the presence of small amounts of oxygen but accelerated by preoxidation of the catalyst. The apparent activation energy, of about 10 kcal. per mole for cuprene growth between 210° and 280 °C., changes to about 40 kcal. per mole above 280 °C. at which temperature a second reaction seems to set in. Hydrogen, carbon monoxide, or nitric oxide has no effect on the reaction velocity. Series of five successive seedings have been obtained with cuprene originally grown on cuprite, and show an effect of aging of the cuprene.

scholarly journals The role of histidine-118 of inorganic pyrophosphatase from thermophilic bacterium PS-3

1991 ◽  
Vol 278 (2) ◽  
pp. 595-599 ◽  
Author(s):  
N Hirano ◽  
T Ichiba ◽  
A Hachimori
Keyword(s):  
Thermophilic Bacterium ◽  
Complete Loss ◽  
Inorganic Pyrophosphatase ◽  
Histidine Residue ◽  
First Order ◽  
Diethyl Pyrocarbonate ◽  
Lysyl Endopeptidase ◽  
First Order Kinetics ◽  
Pseudo First Order

Treatment of the inorganic pyrophosphatase from thermophilic bacterium PS-3 with diethyl pyrocarbonate resulted in the almost complete loss of its activity, which followed pseudo-first-order kinetics. The presence of Mg2+ prevented the inactivation. Enzyme inactivated with diethyl pyrocarbonate was re-activated by hydroxylamine. The inactivation parallelled the amount of modified histidine residue, and a plot of the activity remaining against the amount of modified histidine residue suggested that the modification of one of two histidine residues totally inactivated the enzyme. The site involved was found to be located in a single lysyl endopeptidase-digest peptide derived from the ethoxy[14C]carbonylated enzyme. Amino acid analysis and sequence analysis of the peptide revealed that it comprised residues 96-119 of the inorganic pyrophosphatase from thermophilic bacterium PS-3. These results, when compared with those reported for the Escherichia coli and yeast enzymes, imply that His-118 of the inorganic pyrophosphatase from thermophilic bacterium PS-3 is located near the Mg(2+)-binding site and thus affects the binding of Mg2+.

Thermal reactions of mesityl oxide

1971 ◽  
Vol 24 (5) ◽  
pp. 955 ◽  
Author(s):  
NJ Daly ◽  
MF Gilligan
Keyword(s):  
Carbon Monoxide ◽  
Methyl Bromide ◽  
Hydrogen Bromide ◽  
The Other ◽  
Mesityl Oxide ◽  
Thermal Reactions ◽  
First Order ◽  
First Order Kinetics

Mesityl oxide (4-methylpent-3-en-2-one) thermally decomposes in the range 412-490� give methylbutenes, carbon monoxide, isobutene, and methane as major products. The initial 20% of reaction follows first- order kinetics and is described by the equation k1 = 1014.22exp(-63240/RT) s-1. A Rice-Herzfeld chain is proposed. Addition of hydrogen bromide leads to two reactions, one producing isobutene, carbon monoxide, and methyl bromide, and the other leading to polymerization. Likely steps in the polymerization are proposed.

Aging of Tire Parts during Service. II. Aging of Belt-Skim Rubbers in Passenger Tires

1990 ◽  
Vol 63 (5) ◽  
pp. 698-712 ◽  
Author(s):  
Hiroyuki Kaidou ◽  
A. Ahagon
Keyword(s):  
Activation Energy ◽  
Tensile Properties ◽  
Low Temperatures ◽  
Atmospheric Temperature ◽  
Temperature Fields ◽  
Passenger Car ◽  
Aging Resistance ◽  
Rubber Part ◽  
Higher Temperature

Abstract The belt-skim rubber of a passenger-car tire has changes in its tensile properties, M100 and λb, during service in the field. The changes are larger in higher temperature fields with an equivalent duration. It can be interpreted that the changes are caused simply by oxidative crosslinking similar to that which takes place on aging rubber sheets in an air oven at relatively low temperatures, below 100°C. The belt-skim compound showing better aging resistance in the laboratory also shows better aging resistance when used in a tire. Therefore, the aging characteristics of the rubber part in a tire can be satisfactorily predicted. The Arrhenius equations with the same activation energy can be used for the aging of a rubber in the laboratory and in the tires by introducing a factor to the tire equation. The factor is added to the atmospheric temperature to correct for a difference; however, it was found to be slight in the present case.

scholarly journals The combination of carbon monoxide–haem with apoperoxidase

1969 ◽  
Vol 114 (4) ◽  
pp. 719-724 ◽  
Author(s):  
Charles Phelps ◽  
Eraldo Antonini
Keyword(s):  
Activation Energy ◽  
Carbon Monoxide ◽  
Rate Constant ◽  
Binding Sites ◽  
Order Process ◽  
First Order ◽  
Effects Of Ph ◽  
Kinetics Of

1. Static titrations reveal an exact stoicheiometry between various haem derivatives and apoperoxidase prepared from one isoenzyme of the horseradish enzyme. 2. Carbon monoxide–protohaem reacts rapidly with apoperoxidase and the kinetics can be accounted for by a mechanism already applied to the reaction of carbon monoxide–haem derivatives with apomyoglobin and apohaemoglobin. 3. According to this mechanism a complex is formed first whose combination and dissociation velocity constants are 5×108m−1sec.−1 and 103sec.−1 at pH9·1 and 20°. The complex is converted into carbon monoxide–haemoprotein in a first-order process with a rate constant of 235sec.−1 for peroxidase and 364sec.−1 for myoglobin at pH9·1 and 20°. 4. The effects of pH and temperature were examined. The activation energy for the process of complex-isomerization is about 13kcal./mole. 5. The similarity in the kinetics of the reactions of carbon monoxide–haem with apoperoxidase and with apomyoglobin suggests structural similarities at the haem-binding sites of the two proteins.

scholarly journals Effect of liposomal phospholipid composition on cholesterol transfer between microsomal and liposomal vesicles

1986 ◽  
Vol 238 (3) ◽  
pp. 647-652 ◽  
Author(s):  
C Bhuvaneswaran ◽  
K A Mitropoulos
Keyword(s):  
Activation Energy ◽  
Enzyme Activity ◽  
Control System ◽  
Phospholipid Composition ◽  
Acyltransferase Activity ◽  
Phosphatidylcholine Liposomes ◽  
First Order ◽  
First Order Kinetics ◽  
Phospholipid Liposomes

Preincubation of rat liver microsomal vesicles at 37 degrees C in the presence of [3H]cholesterol/phospholipid liposomes results in a net transfer of cholesterol from liposomes to microsomal vesicles. This transfer follows first-order kinetics. For similar concentrations of the donor vesicles, rates of transfer are about 6-8 times lower with cholesterol/sphingomyelin liposomes compared with cholesterol/phosphatidylcholine liposomes. Also, transfer of cholesterol from cholesterol/sphingomyelin liposomes to microsomal vesicles reveals a larger activation energy than for the process from cholesterol/phosphatidylcholine liposomes. There is a significant correlation between the amount of liposomal cholesterol transferred to microsomal vesicles during preincubation and the increase found with acyl-CoA:cholesterol acyltransferase activity in these microsomes over their corresponding controls. If, however, liposomes made solely of phospholipids are substituted for the cholesterol/phospholipid liposomes in the preincubation system containing microsomal vesicles, then the acyl-CoA:cholesterol acyltransferase activity is decreased compared with the corresponding control system. Both sphingomyelin and phosphatidylcholine liposomes are equally effective in decreasing the enzyme activity. These results offer direct kinetic evidence for the positive correlation between cholesterol and sphingomyelin found in vivo in biological membranes.

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