The Rate constant of the Reaction of OH(A2Σ+) with H2O2(X˜1A)

2001 ◽  
Vol 215 (7) ◽  
Author(s):  
Walter Hack ◽  
R. Jordan
Keyword(s):  
Rate Constant ◽  
Room Temperature ◽  
Order Conditions ◽  
Oh Radicals ◽  
Quenching Rate ◽  
First Order ◽  
Electronically Excited State ◽  
Electronically Excited ◽  
Quenching Rate Constant ◽  
Pseudo First Order

The rate constant of the depletion of OH radicals in the first electronically excited state with hydrogenperoxid:OH(was determined at room temperature under pseudo first-order conditions [OH(The rate constant is:similar to the quenching rate constant of OH(

Photolysis of 2,5- and 2,4-Dimethylpyrrole Vapors at Room Temperature

1972 ◽  
Vol 50 (11) ◽  
pp. 1678-1689 ◽  
Author(s):  
E. Chung Wu ◽  
Julian Heicklen
Keyword(s):  
Excited State ◽  
Free Radical ◽  
Room Temperature ◽  
Low Pressure ◽  
Incident Radiation ◽  
Ring Cleavage ◽  
Incident Wavelength ◽  
First Order ◽  
Electronically Excited State ◽  
Electronically Excited

Both 2,5- and 2,4-dimethylpyrrole vapors at pressures from 0.05 to 0.70 Torr were irradiated at 2139 and 2288 Å at room temperature. The products were H2, CH4, C2H6, and polymer. No ring cleavage products were found. Φ{H2} and Φ{CH4} were remarkably insensitive to which pyrrole was used, its pressure,Ia, or the wavelength of the incident radiation. They were ~0.10–0.15 and ~0.01–0.02, respectively. Φ{C2H6} was comparable to Φ{CH4} and was also invariant to which substrate was used or the incident wavelength. However Φ{C2H6} did increase at low pressure or as Ia was reduced.The effect of scavengers showed that the products were produced mainly from free radical precursors. The main primary steps are:[Formula: see text]where DMP* is an electronically excited state of the dimethylpyrrole and Fa and Fb are radical fragments. Experiments with quenching gases showed that DMP* could be quenched, but that this reaction was less important than the first-order steps below 1 Torr.

scholarly journals Rate coefficients for the reaction of methylglyoxal (CH<sub>3</sub>COCHO) with OH and NO<sub>3</sub> and glyoxal (HCO)<sub>2</sub> with NO<sub>3</sub>

2011 ◽  
Vol 11 (21) ◽  
pp. 10837-10851 ◽  
Author(s):  
R. K. Talukdar ◽  
L. Zhu ◽  
K. J. Feierabend ◽  
J. B. Burkholder
Keyword(s):  
Relative Rate ◽  
Order Conditions ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
First Order ◽  
No3 Radical ◽  
Pseudo First Order ◽  
Arrhenius Expression ◽  
Coefficient Method

Abstract. Rate coefficients, k, for the gas-phase reaction of CH3COCHO (methylglyoxal) with the OH and NO3 radicals and (CHO)2 (glyoxal) with the NO3 radical are reported. Rate coefficients for the OH + CH3COCHO (k1) reaction were measured under pseudo-first-order conditions in OH as a function of temperature (211–373 K) and pressure (100–220 Torr, He and N2 bath gases) using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to measure its temporal profile. k1 was found to be independent of the bath gas pressure with k1(295 K) = (1.29 ± 0.13) × 10−11 cm3 molecule−1 s−1 and a temperature dependence that is well represented by the Arrhenius expression k1(T) = (1.74 ± 0.20) × 10−12 exp[(590 ± 40)/T] cm3 molecule−1 s−1 where the uncertainties are 2σ and include estimated systematic errors. Rate coefficients for the NO3 + (CHO)2 (k3) and NO3 + CH3COCHO (k4) reactions were measured using a relative rate technique to be k3(296 K) = (4.0 ± 1.0) × 10−16 cm3 molecule−1 s−1 and k4(296 K) = (5.1 ± 2.1) × 10−16 cm3 molecule−1 s−1. k3(T) was also measured using an absolute rate coefficient method under pseudo-first-order conditions at 296 and 353 K to be (4.2 ± 0.8) × 10−16 and (7.9 ± 3.6) × 10−16 cm3 molecule−1 s−1, respectively, in agreement with the relative rate result obtained at room temperature. The atmospheric implications of the OH and NO3 reaction rate coefficients measured in this work are discussed.

scholarly journals Rate coefficients for the reaction of methylglyoxal (CH<sub>3</sub>COCHO) with OH and NO<sub>2</sub> and glyoxal (HCO)<sub>2</sub> with NO<sub>3</sub>

2011 ◽  
Vol 11 (6) ◽  
pp. 18211-18248
Author(s):  
R. K. Talukdar ◽  
L. Zhu ◽  
K. J. Feierabend ◽  
J. B. Burkholder
Keyword(s):  
Relative Rate ◽  
Order Conditions ◽  
Rate Coefficients ◽  
Oh Radicals ◽  
Phase Reaction ◽  
First Order ◽  
No3 Radical ◽  
Pseudo First Order ◽  
Arrhenius Expression ◽  
Coefficient Method

Abstract. Rate coefficients, k, for the gas-phase reaction of CH3COCHO (methylglyoxal) with the OH and NO3 radicals and (CHO)2 (glyoxal) with the NO3 radical are reported. Rate coefficients for the OH + CH3COCHO (k1) reaction were measured under pseudo-first-order conditions in OH as a function of temperature (211–373 K) and pressure (100–220 Torr, He and N2 bath gases) using pulsed laser photolysis to produce OH radicals and laser induced fluorescence to measure its temporal profile. k1 was found to be independent of the bath gas pressure with k1(295 K) = (1.29 ± 0.13) × 10−11 cm3 molecule−1 s−1 and a temperature dependence that is well represented by the Arrhenius expression k1(T) = (1.74 ± 0.20) × 10−12 exp[(590 ± 40)/T] cm3 molecule−1 s−1 where the uncertainties are 2σ and include estimated systematic errors. Rate coefficients for the NO3+ (CHO)2 (k3) and NO3+ CH3COCHO (k4) reactions were measured using a relative rate technique to be k3(296 K) = (3.7 ± 1.0) × 10−16 cm3 molecule−1 s−1 and k4(296 K) = (4.1 ± 1.2) × 10−16 cm3 molecule−1 s−1. k3(T) was also measured using an absolute rate coefficient method under pseudo-first-order conditions at 296 and 353 K to be (4.2 ± 0.8) × 10−16 and (7.9 ± 3.6) × 10−16 cm3 molecule−1 s−1, respectively, in agreement with the relative rate result obtained at room temperature. The atmospheric implications of the OH and NO3 reaction rate coefficients measured in this work are discussed.

Fluorescence quenching in micelles: A theoretical model for the intramicellar first order quenching rate constant

1981 ◽  
Vol 74 (2) ◽  
pp. 1140-1147 ◽  
Author(s):  
M. Van der Auweraer ◽  
J. C. Dederen ◽  
E. Geladé ◽  
F. C. De Schryver
Keyword(s):  
Theoretical Model ◽  
Fluorescence Quenching ◽  
Rate Constant ◽  
Quenching Rate ◽  
First Order ◽  
Quenching Rate Constant

scholarly journals Ligand Exchange Kinetics of 2,2’-Bipyridine with Nitrilotriacetatonickelate(II)

2018 ◽  
Vol 6 (2) ◽  
pp. 71-75
Author(s):  
Larry H Kolopajlo ◽  
Shelby Coleman
Keyword(s):  
Rate Constant ◽  
Ligand Exchange ◽  
Order Conditions ◽  
Hydrogen Ion ◽  
Ligand Exchange Reaction ◽  
First Order ◽  
Exchange Kinetics ◽  
Pseudo First Order ◽  
Ph Range ◽  
Kinetics Of

The kinetics of the ligand exchange reaction between 2,2’-bipyridine (bipy) and NiNTA- was studied over the pH range 4.7 to 7.5 at 25.0 0C and an ionic strength of 0.10 M by following the formation of Ni(bipy)3 product at 307 nm. All reactions were run under pseudo-first order conditions with a [bipy]/[NiNTA-] ratio of at least 20. The reaction is first-order with respect to each of NiNTA- and to bipy. The reaction is also accelerated by hydrogen ion. The rate constant for the hydrogen ion unassisted addition of bipy to NiNTA- is 0.671 M-1 s-1. The reaction is also first-order in hydrogen ion with a rate constant for the hydrogen ion assisted addition of bipy to NiNTA- is 9.45 x 104 M-2 s-1. A dissociative type mechanism accelerated by hydrogen ion is proposed. The work has significance by showing that NiEDDA and NiNTA, both aminopolyacrboxylate complexes react by the same mechanism.

Temperature dependence of the O+I(P21/2)→O+I(P23/2) quenching rate constant

2009 ◽  
Vol 105 (9) ◽  
pp. 094911 ◽  
Author(s):  
Pavel A. Mikheyev ◽  
David J. Postell ◽  
Michael C. Heaven
Keyword(s):  
Temperature Dependence ◽  
Rate Constant ◽  
Quenching Rate ◽  
Quenching Rate Constant

Kinetics of reconstitution of apotyrosinase by copper

1990 ◽  
Vol 68 (2) ◽  
pp. 476-479
Author(s):  
Donald C. Wigfield ◽  
Douglas M. Goltz
Keyword(s):  
Rate Constant ◽  
Copper Concentration ◽  
Copper Ions ◽  
Copper Ion ◽  
Order Rate Constant ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Rate Limiting ◽  
Kinetics Of

The kinetics of the reconstitution reaction of apotyrosinase with copper (II) ions are reported. The reaction is pseudo first order with respect to apoenzyme and the values of these pseudo first order rate constants are reported as a function of copper (II) concentration. Two copper ions bind to apoenzyme, and if the second one is rate limiting, the kinetically relevant copper concentration is the copper originally added minus the amount used in binding the first copper ion to enzyme. This modified copper concentration is linearly related to the magnitude of the pseudo first order rate constant, up to a copper concentration of 1.25 × 10−4 M (10-fold excess), giving a second order rate constant of 7.67 × 102 ± 0.93 × 102 M−1∙s−1.Key words: apotyrosinase, copper, tyrosinase.

scholarly journals Acrolein, an irreversible active-site-directed inhibitor of deoxyribose 5-phosphate aldolase?

1976 ◽  
Vol 153 (2) ◽  
pp. 495-497 ◽  
Author(s):  
D C Wilton
Keyword(s):  
Schiff Base ◽  
Rate Constant ◽  
Active Site ◽  
Order Rate Constant ◽  
Lysine Residue ◽  
Prolonged Incubation ◽  
Enzyme Active Site ◽  
First Order ◽  
Substrate Analogue ◽  
Pseudo First Order

The enzyme deoxyribose 5-phosphate aldolase was irreversibly inactivated by the substrate analogue acrolein with a pseudo-first-order rate constant of 0.324 min-1 and a Ki (apparent) of 2.7 × 10(-4) m. No inactivation was observed after prolonged incubation with the epoxide analogues glycidol phosphate and glycidaldehyde. It is suggested that the acrolein is first activated by forming a Schiff base with the enzyme active-site lysine residue and it is the activated inhibitor that reacts with a suitable-active-site nucleophile.

An automated approach to characterize, in simple kinetic terms, the generation and inactivation of thrombin and the interaction of fibrinogen with thrombin.

1988 ◽  
Vol 34 (10) ◽  
pp. 1971-1975 ◽  
Author(s):  
D R Hoak ◽  
S K Banerjee ◽  
G Kaldor
Keyword(s):  
Prothrombin Time ◽  
Rate Constant ◽  
Thrombin Generation ◽  
Order Rate Constant ◽  
Clinical Use ◽  
First Order ◽  
Pathological Conditions ◽  
Pseudo First Order ◽  
Instantaneous Concentration

Abstract Here, we used a fully automated, computer-directed centrifugal analyzer (which permitted simultaneous turbidimetry and calculation of results) and purified thrombin, fibrinogen, and various inhibitors to study clot formation. The Km and Vm for these reactions were useful in detecting and partly characterizing anticoagulants. We also explored the generation and inactivation of thrombin, using the two-stage prothrombin time and antithrombin activity tests. The amount of thrombin instantaneously generated and inactivated was monitored under artificially created pathological conditions. The pseudo-first-order rate constant for thrombin generation and inactivation and the instantaneous concentration of enzymatically active and inactive thrombin were used in the characterization of these conditions. We believe this approach is suitable for routine clinical use.

scholarly journals Inactivation of the endogenous argininosuccinate lyase activity of duck δ-crystallin by modification of an essential histidine residue with diethyl pyrocarbonate

1993 ◽  
Vol 293 (2) ◽  
pp. 537-544 ◽  
Author(s):  
H J Lee ◽  
S H Chiou ◽  
G G Chang
Keyword(s):  
Enzyme Activity ◽  
Rate Constant ◽  
Order Rate Constant ◽  
Histidine Residue ◽  
Argininosuccinate Lyase ◽  
First Order ◽  
Diethyl Pyrocarbonate ◽  
Order Rate ◽  
Lyase Activity ◽  
Pseudo First Order

The argininosuccinate lyase activity of duck delta-crystallin was inactivated by diethyl pyrocarbonate at 0 degrees C and pH 7.5. The inactivation followed pseudo-first-order kinetics after appropriate correction for the decomposition of the reagent during the modification period. The plot of the observed pseudo-first-order rate constant versus diethyl pyrocarbonate concentration in the range of 0.17-1.7 mM was linear and went through the origin with a second-order rate constant of 1.45 +/- 0.1 M-1.s-1. The double-logarithmic plot was also linear, with slope of 1.13, which suggested a 1:1 stoichiometry for the reaction between diethyl pyrocarbonate and delta-crystallin. L-Arginine, L-norvaline or L-citrulline protected the argininosuccinate lyase activity of delta-crystallin from diethyl pyrocarbonate inactivation. The dissociation constants for the delta-crystallin-L-arginine and delta-crystallin-L-citrulline binary complexes, determined by the protection experiments, were 4.2 +/- 0.2 and 0.12 +/- 0.04 mM respectively. Fumarate alone had no protective effect. However, fumarate plus L-arginine gave synergistic protection with a ligand binding interacting factor of 0.12 +/- 0.02. The double-protection data conformed to a random Uni Bi kinetic mechanism. Fluorescence-quenching studies indicated that the modified delta-crystallin had minimum, if any, conformational changes as compared with the native delta-crystallin. Inactivation of the enzyme activity was accompanied by an increasing absorbance at 240 nm of the protein. The absorption near 280 nm did not change. Treatment of the modified protein with hydroxylamine regenerated the enzyme activity to the original level. These results strongly indicated the modification of an essential histidine residue. Calculation from the 240 nm absorption changes indicated that only one histidine residue per subunit was modified by the reagent. This super-active histidine residue has a pKa value of approximately 6.8 and acts as a general acid-base catalyst in the enzyme reaction mechanism. Our experimental data are compatible with an E1cB mechanism [Raushel (1984) Arch. Biochem. Biophys. 232, 520-525] for the argininosuccinate lyase with the essential histidine residue close to the arginine-binding domain of delta-crystallin. L-Citrulline, after binding to this domain, might form an extra hydrogen bond with the essential histidine residue.

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