Quasi-classical rate constants for the inelastic process O2(υi≫ 1) + O2→ O2(υf) + O2

2000 ◽  
Vol 98 (21) ◽  
pp. 1729-1735 ◽  
Author(s):  
~José Campos-Martínez ◽  
Estela Carmona-Novillo ◽  
Julián Echave ◽  
Marta I. Hernández ◽  
Juliana Palma
1988 ◽  
Vol 60 (02) ◽  
pp. 247-250 ◽  
Author(s):  
H R Lijnen ◽  
L Nelles ◽  
B Van Hoef ◽  
F De Cock ◽  
D Collen

SummaryRecombinant chimaeric molecules between tissue-type plasminogen activator (t-PA) and single chain urokinase-type plasminogen activator (scu-PA) or two chain urokinase-type plasminogen activator (tcu-PA) have intact enzymatic properties of scu-PA or tcu-PA towards natural and synthetic substrates (Nelles et al., J Biol Chem 1987; 262: 10855-10862). In the present study, we have compared the reactivity with inhibitors of both the single chain and two chain variants of recombinant u-PA and two recombinant chimaeric molecules between t-PA and scu-PA (t-PA/u-PA-s: amino acids 1-263 of t-PA and 144-411 of u-PA; t-PA/u-PA-e: amino acids 1-274 of t-PA and 138-411 of u-PA). Incubation with human plasma in the absence of a fibrin clot for 3 h at 37° C at equipotent concentrations (50% clot lysis in 2 h), resulted in significant fibrinogen breakdown (to about 40% of the normal value) for all two chain molecules, but not for their single chain counterparts. Preincubation of the plasminogen activators with plasma for 3 h at 37° C, resulted in complete inhibition of the fibrinolytic potency of the two chain molecules but did not alter the potency of the single chain molecules. Inhibition of the two chain molecules occurred with a t½ of approximately 45 min. The two chain variants were inhibited by the synthetic urokinase inhibitor Glu-Gly-Arg-CH2CCl with apparent second-order rate constants of 8,000-10,000 M−1s−1, by purified α2-antiplasmin with second-order rate constants of about 300 M−1s−1, and by plasminogen activator inhibitor-1 (PAI-1) with second-order rate constants of approximately 2 × 107 M−1s−1.It is concluded that the reactivity of single chain and two chain forms of t-PA/u-PA chimaers with inhibitors is very similar to that of the single and two chain forms of intact u-PA.


1977 ◽  
Vol 38 (03) ◽  
pp. 0677-0684 ◽  
Author(s):  
Raymund Machovich ◽  
Péter Arányi

SummaryHeat inactivation of thrombin at 54° C followed first order kinetics with a rate constant of 1.0 min−1 approximately. Addition of heparin resulted in protection against thermal denaturation and, at the same time, rendered denaturation kinetics more complex. Analysis of the biphasic curve of heat inactivation in the presence of heparin revealed that the rate constants of the second phase changed systematically with heparin concentrations. Namely, at 4.5 × 10−6M, 9 × 10−6M, 1.8 × 10−5M and 3.6 × 10−5M heparin concentrations, the rate constants were 0.27 min−1, 0.17 min−1, 0.11 min−1 and 0.06 min−1, respectively.Sulfate as well as phosphate ions displayed also enzyme protection against heat inactivation, however, the same effect was obtained already at a heparin concentration, lower by three orders of magnitude.The kinetics of enzyme denaturation was not affected by calcium ions, whereas in the presence of heparin the inactivation rate of thrombin changed, i. e. calcium ions abolished the biphasic character of time course of thermal denaturation.Thus, the data suggest that calcium ions contribute to the effect of heparin on thrombin.


2009 ◽  
Vol 44 (3) ◽  
pp. 253-262 ◽  
Author(s):  
Jes Vollertsen ◽  
Svein Ole Åstebøl ◽  
Jan Emil Coward ◽  
Tor Fageraas ◽  
Asbjørn Haaning Nielsen ◽  
...  

Abstract A wet detention pond in Norway has been monitored for 12 months. The pond receives runoff from a highway with a traffic load of 42,000 average daily traffic. Hydraulic conditions in terms of inflow, outflow, and pond water level were recorded every minute. Water quality was monitored by volume proportional inlet and outlet samples. During most of the year, excellent pollutant removal was achieved; however, during two snowmelt events the pollutant removal was poor or even negative. The two snowmelt events accounted for one third of the annual water load and for a substantial part of the annual pollutant discharge. The performance of the pond was analyzed using a dynamic model and pollutant removal was simulated by first-order kinetics. Good agreement between measurement and simulation could be achieved only when choosing different first-order rate constants for different parts of the year. However, no relation between the rate constants obtained and the time of year could be identified, and neither did the rate constants for different pollutants correlate. The study indicates that even detailed measurements of pollutant input and output allow only average performance to be simulated and are insufficient for simulating event-based variability in pond performance.


1994 ◽  
Vol 30 (11) ◽  
pp. 143-146
Author(s):  
Ronald D. Neufeld ◽  
Christopher A. Badali ◽  
Dennis Powers ◽  
Christopher Carson

A two step operation is proposed for the biodegradation of low concentrations (< 10 mg/L) of BETX substances in an up flow submerged biotower configuration. Step 1 involves growth of a lush biofilm using benzoic acid in a batch mode. Step 2 involves a longer term biological transformation of BETX. Kinetics of biotransformations are modeled using first order assumptions, with rate constants being a function of benzoic acid dosages used in Step 1. A calibrated computer model is developed and presented to predict the degree of transformation and biomass level throughout the tower under a variety of inlet and design operational conditions.


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