scholarly journals Effect of heparin on thrombin inactivation by antithrombin-III

1978 ◽  
Vol 173 (3) ◽  
pp. 869-875 ◽  
Author(s):  
R Machovich ◽  
P Arányi
Keyword(s):  
Antithrombin Iii ◽  
Specific Activity ◽  
Activation Parameters ◽  
Heat Inactivation ◽  
Activation Entropy ◽  
First Order ◽  
Heparin Concentration ◽  
First Order Kinetics ◽  
Thermodynamic Activation Parameters ◽  
Time Courses

The inactivation of thrombin by heat and by its physiological inhibitor, antithrombin-III, shows quite different dependence on heparin concentration. Heparin at 250 microgram/ml protects thrombin against heat inactivation, and thrombin behaves heterogeneously in this reaction. In the absence of heparin, the thermodynamic activation parameters change with temperature (deltaH+ = 733 kJ/mol and 210 kJ/mol at 50 and 58 degrees C respectively). When heparin is present, heat inactivation of the protected thrombin species proceeds with deltaH+ = 88 kJ/mol and is independent of temperature in the same range. On the other hand, heparin at 0.125-2.5 microgram/ml accelerates the thrombin-antithrombin-III reaction. Thrombin does not show heterogeneity in this reaction and the time courses at any heparin concentration and any temperature between 0 and 37 degrees C appear to follow first-order kinetics. Activation enthalpy is independent of heparin concentration or temperature, deltaH+ = 82-101 kJ/mol, varying slightly with antithrombin-III concentration and thrombin specific activity. Heparin seems to exert its effect by increasing activation entropy. On the basis of these data we suggest a mechanism of action of heparin in the thrombin-antithrombin-III reaction which accounts for all the important features of the latter and seems to unify the different hypotheses that have been advanced.

scholarly journals A kinetic study of Zn halide/TBAB-catalysed fixation of CO2 with styrene oxide in propylene carbonate

2019 ◽  
Vol 8 (1) ◽  
pp. 719-729 ◽  
Author(s):  
Abdul Rehman ◽  
M.F.M. Gunam Resul ◽  
Valentine C. Eze ◽  
Adam Harvey
Keyword(s):  
Propylene Carbonate ◽  
Styrene Oxide ◽  
Activation Parameters ◽  
Green Solvent ◽  
Acid Base ◽  
First Order ◽  
First Order Kinetics ◽  
Thermodynamic Activation Parameters ◽  
Styrene Carbonate ◽  
Comprehensive Study

Abstract Synthesis of styrene carbonate (SC) via the fixation of CO2 with styrene oxide (SO) has been investigated using a combination of zinc bromide (ZnBr2) and tetrabutylammonium halides (TBAX) as acid-base binary homogeneous catalysts. The combination of ZnBr2 and TBAB had a synergistic effect, which led to about 6-fold enhancement in the rate of SC formation as compared to using TBAB alone as a catalyst. Propylene carbonate (PC) was chosen as a green solvent for a comprehensive study of reaction kinetics. The reaction followed a first-order kinetics with respect to SO, CO2, and TBAB, whereas a fractional order was observed for the ZnBr2 when used in combination with the TBAB. Arrhenius and Eyring’s expressions were applied to determine the kinetic and thermodynamic activation parameters, where activation energy (Ea) of 23.3 kJ mol−1 was obtained for the SC formation over the temperature range of 90-120°C. The thermodynamic analysis showed that positive values for enthalpy (ΔH‡ = 18.53 kJ mol−1), Gibbs free energy (ΔG‡ = 79.74 kJ mol−1), whereas a negative entropy (ΔS‡ = –162.88 J mol−1 K−1) was obtained. These thermodynamic parameters suggest that endergonic and kinetically controlled reactions were involved in the formation of SC from SO and CO2.

Solvent Effects on the Racemization of Optically Active Tris(N-substituted carbamodithioato)cobalt (III) Complexes

1979 ◽  
Vol 32 (8) ◽  
pp. 1653 ◽  
Author(s):  
LR Gahan ◽  
MJ O'Conner
Keyword(s):  
Carbon Tetrachloride ◽  
Solvent Effects ◽  
Reaction Mechanisms ◽  
Activation Parameters ◽  
Optically Active ◽  
Isokinetic Relationship ◽  
First Order ◽  
First Order Kinetics ◽  
Thermodynamic Activation Parameters ◽  
Wide Range

The thermal racemization in solution of some optically active tris(N-substituted carbamodithioato)- cobalt(III) complexes [N-substituents = diphenyl, dimethyl, diisopropyl, and tetramethylene (pyrrolidinyl)] has been measured polarimetrically in a range of solvents including dimethylformamide, acetonitrile, carbon tetrachloride, chlorobenzene, chloroform, toluene and ethanol. The metal-centred (Δ ↔ Λ) inversion reactions show first-order kinetics as expected for an intra- molecular process. Thermodynamic activation parameters for the reaction show that values of ΔS‡ occur over a wide range (from -124 to +60 J K-1 mol-1) as do the values of ΔH‡ (from 67�4 to 129�3 kJ mol-1). Values for ΔG‡ are reasonably constant. Although a similar mechanism for the metal-centred inversion is suggested for all compounds in the various solvents because of an observed isokinetic relationship between ΔH‡ and ΔS‡, with isokinetic temperatures in the range 312-369 K, it is clear that postulates of reaction mechanisms based on the value of ΔS‡ determined in only one solvent should be treated with caution. The optically active (-)546-tris(N,N-diisopropylcarbamodithioato)cobalt(III) complex photoracemizes in solution without decomposition. The rate of photoracemization is solvent-dependent being in the order bromoform � carbon tetrachloride ≈ chloroform �benzene.

Kinetic Studies of [4n+2]π-Thermal Cyclodimerization of 1-(3-Pyridazinyl)-3-oxidopyridinium Betaines

1992 ◽  
Vol 57 (9) ◽  
pp. 1951-1959 ◽  
Author(s):  
Madlene L. Iskander ◽  
Samia A. El-Abbady ◽  
Alyaa A. Shalaby ◽  
Ahmed H. Moustafa
Keyword(s):  
Energy Gap ◽  
Activation Parameters ◽  
Kinetic Studies ◽  
Cyclic Transition ◽  
Concerted Mechanism ◽  
First Order ◽  
Thermodynamic Activation Parameters ◽  
Cyclic Transition State ◽  
Complete Dissociation ◽  
Homo Lumo

The reactivity of the base induced cyclodimerization of 1-(6-arylpyridazin-3-yl)-3-oxidopyridinium chlorides in a pericyclic process have been investigated kinetically at λ 380 nm. The reaction was found to be second order with respect to the liberated betaine and zero order with respect to the base. On the other hand dedimerization (monomer formation) was found to be first order. It was shown that dimerization is favoured at low temperature, whereas dedimerization process is favoured at relatively high temperature (ca 70 °C). Solvent effects on the reaction rate have been found to follow the order ethanol > chloroform ≈ 1,2-dichloroethane. Complete dissociation was accomplished only in 1,2-dichloroethane at ca 70 °C. The thermodynamic activation parameters have been calculated by a standard method. Thus, ∆G# has been found to be independent on substituents and solvents. The high negative values of ∆S# supports the cyclic transition state which is in favour with the concerted mechanism. MO calculations using SCF-PPP approximation method indicated low HOMO-LUMO energy gap of the investigated betaines.

Use of purified lyophilized human lactate dehydrogenase isoenzyme 5 in a study of measuring lactate dehydrogenase activity.

1989 ◽  
Vol 35 (8) ◽  
pp. 1774-1776 ◽  
Author(s):  
D A Smith ◽  
G C Moses ◽  
A R Henderson
Keyword(s):  
Lactate Dehydrogenase ◽  
Half Life ◽  
Specific Activity ◽  
Lactate Dehydrogenase Activity ◽  
Bovine Albumin ◽  
First Order ◽  
First Order Kinetics ◽  
The Stability ◽  
Lactate Dehydrogenase Isoenzymes ◽  
Excellent Stability

Abstract We examined the stability of human lactate dehydrogenase (EC 1.1.1.27) isoenzyme 5--purified to a specific activity of about 400 kU/g--when lyophilized in a buffered, stabilized matrix of bovine albumin. This isoenzyme was prepared with a final activity of about 500 U/L and stored at -20, 4, 20, 37, and 56 degrees C for as long as six months. This isoenzyme decayed with approximate first-order kinetics, with an estimated half-life at -20 degrees C of about 475 years. Stability of reconstituted samples stored at 20 or 4 degrees C was poor, suggesting that the reconstituted material should be used without delay; material stored at -20 degrees C showed excellent stability for 15 days. We propose that such preparations might be further investigated as standards for use in electrophoresis of lactate dehydrogenase isoenzymes.

The kinetics and the mechanism of oxidative decarboxylation of benzilic acid by acidic permanganate (stopped-flow technique) — An autocatalytic study

2004 ◽  
Vol 82 (9) ◽  
pp. 1372-1380 ◽  
Author(s):  
Sairabanu A Farokhi ◽  
Sharanappa T Nandibewoor
Keyword(s):  
Activation Parameters ◽  
Oxidative Decarboxylation ◽  
Two Stage ◽  
First Order ◽  
First Order Kinetics ◽  
Stage Process ◽  
Benzilic Acid ◽  
Reaction Constants ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of the oxidation of benzilic acid by potassium permanganate in an acidic medium were studied spectrophotometrically. The reaction followed a two-stage process, wherein both stages of the reaction followed first-order kinetics with respect to permanganate ion and benzilic acid. The rate of the reaction increased with an increase in acid concentration. Autocatalysis was observed by one of the products, i.e., manganese(II). A composite mechanism involving autocatalysis has been proposed. The activation parameters of the reaction were calculated and discussed and the reaction constants involved in the mechanisms were calculated. There is a good agreement between the observed and calculated rate constants under different experimental conditions.Key words: oxidation, autocatalysis, benzilic acid, two-stage kinetics.

scholarly journals CATION EXCHANGE BETWEEN CELLS AND PLASMA OF MAMMALIAN BLOOD

1950 ◽  
Vol 33 (6) ◽  
pp. 703-722 ◽  
Author(s):  
C. W. Sheppard ◽  
W. R. Martin
Keyword(s):  
Exchange Rate ◽  
Radioactive Isotope ◽  
Specific Activity ◽  
Compartment System ◽  
First Order ◽  
First Order Kinetics ◽  
Mammalian Blood ◽  
The Mean ◽  
Pseudo First Order

The exchange of potassium between cells and plasma of heparinized human blood has been studied in vitro using the radioactive isotope K42. The changes in cell and plasma specific activity are characteristic of a simple two-compartment system. The mean of seven determinations of the exchange rate at 38°C. is 1.8 per cent of the cellular potassium per hour. The results indicate that at 38°C. the rate is relatively insensitive to oxygenation or reduction of the hemoglobin, and to 1200 r of gamma radiation. With varying temperature the rate follows pseudo first order kinetics with a Q10 of 2.35. Below 15°C. the rate of loss of potassium exceeds the rate of uptake.

scholarly journals Kinetics and Mechanism of Oxidation of Diethanolamine and Triethanolamine by Potassium Ferrate

2011 ◽  
Vol 8 (2) ◽  
pp. 903-909 ◽  
Author(s):  
Shan Jinhuan ◽  
Zhang Jiying
Keyword(s):  
Activation Parameters ◽  
Rate Equations ◽  
Potassium Ferrate ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Order Dependence ◽  
Rate Determining Step ◽  
Thermodynamic Activation Parameters ◽  
Plausible Mechanism ◽  
Kinetics Of

The kinetics of oxidation of diethanolamine and triethanolamine by potassium ferrate(VI)in alkaline liquids at a constant ionic strength has been studied spectrophotometrically in the temperature range of 278.2K-293.2K. The reaction shows first order dependence on potassium ferrate(VI), first order dependence on each reductant, The observed rate constant (kobs) decreases with the increase in [OH-], the reaction is negative fraction order with respect to [OH-]. A plausible mechanism is proposed and the rate equations derived from the mechanism can explain all the experimental results. The rate constants of the rate-determining step and the thermodynamic activation parameters are calculated.

scholarly journals KINETICS OF REACTION BETWEEN MALACHITE GREEN AND HYDROXYL ION IN THE PRESENCE OF REDUCING SUGARS

2015 ◽  
Vol 23 (23) ◽  
pp. 61-72
Author(s):  
Dayo Felix Latona ◽  
Adewumi Oluwasogo Dada
Keyword(s):  
Malachite Green ◽  
Activation Parameters ◽  
Cell Compartment ◽  
First Order ◽  
Rate Determining Step ◽  
First Order Kinetics ◽  
Hydroxyl Ion ◽  
Kinetics Of Reaction ◽  
Kinetics Of ◽  
Sphere Mechanism

The reaction was studied via pseudo-first-order kinetics using a UV-1800 Shimadzu spectrophotometer with a thermostated cell compartment and interfaced with a computer. The reaction showed first order with respect to malachite green and sugar and hydroxyl ion concentrations. However, the reaction was independent of ionic strength and showed no dependence on the salt effect, indicating an inner sphere mechanism for the reaction. There was no polymerization of the reaction mixture with acrylonitrile, indicating the absence of radicals in the course of the reaction. Michaelis-Menten plot indicated the presence of a reaction intermediate in the rate-determining step. The activation parameters of the reaction have been calculated and products were elucidated by FTIR spectroscopy. The stoichiometry of the reaction is 1:1. A mechanism consistent with the above facts has been suggested.

scholarly journals Thermal inactivation studies of normal and variant human erythrocyte carbonic anhydrases by using a sulphonamide-binding assay

1974 ◽  
Vol 141 (1) ◽  
pp. 219-225 ◽  
Author(s):  
William R. A. Osborne ◽  
Richard E. Tashian
Keyword(s):  
Thermal Inactivation ◽  
Activation Parameters ◽  
Energy Of Activation ◽  
Heat Inactivation ◽  
Activation Entropy ◽  
Carbonic Anhydrases ◽  
Compensating Variation ◽  
Arrhenius Plots ◽  
Heat Stable ◽  
Free Energy Of Activation

Heat-inactivation studies were carried out on the two primary erythrocyte carbonic anhydrase isoenzymes, CA I and CA II, and the secondary isoenzyme of CA I, CA I (+1). In addition, two genetic variants of human isoenzyme CA I, CA Id Michigan (100 Thr→Lys) and CA If London (102 Glu→Lys), and one variant of isoenzyme CA II, CA IIh (251 Asn→Asp), were similarly analysed. The first-order rate constants and Arrhenius plots for these six enzyme forms showed that (1) isoenzyme CA II is more heat-stable than CA I, (2) isoenzyme CA I (+1) is less heat-stable than CA I, (3) the variants CA IIh and CA If London are less heat-stable than the normal enzymes, and (4) isoenzyme CA Id Michigan is more heat-stable than normal CA I. From the values of the slopes of the Arrhenius plots, the energy of activation (Ea) for each isoenzyme and isoenzyme variant was determined, and the following thermodynamic activation parameters were calculated at 55°C: the free energy of activation (ΔG‡), the activation enthalpy (ΔH‡) and the activation entropy (ΔS‡). The ΔG‡ for the enzymes shows a relative constancy with compensating variation in ΔH‡ and ΔS‡. When the values for ΔH‡ are plotted against ΔS‡, an increase in ΔH‡ involves a concomitant increase in ΔS‡.

KINETICS OF HEPARIN CO-FACTOR II (HCII):THROMBIN AND ANTITHROMBIN III (ATIII):THROMBIN INTERACTION. MOLECULAR WEIGHT DEPENDENCY

1987 ◽  
Author(s):  
V E Ellis ◽  
M F Scully ◽  
V V Kakkar
Keyword(s):  
Unfractionated Heparin ◽  
Antithrombin Iii ◽  
Binding Affinities ◽  
Peak Acceleration ◽  
First Order ◽  
High Affinity ◽  
Heparin Concentration ◽  
Factor Ii ◽  
Kinetics Of ◽  
Stimulation Of

The influence of increasing concentrations of heparin of different molecular mass (Mr) has been compared in potentiation of the rate of HCII:thrombin interaction and of ATIII:thrombin interaction under pseudo first order conditions. Unfractionated and fractionated heparin showed a concentration dependent ascending and descending limb of stimulation of the rate which was closely similar for both inhibitors. Unfractionated heparin and fractions of 16.5 KDa or less showed a peak acceleration of the rate of interaction of thrombin with both inhibitors at 0.3×10−6 heparin although the observed maximum rate at this peak decreased with fall in Mr. For both inhibitors two high Mr fractions (22KDa and 32KDa) showed peak stimulation at a lower heparin concentration (0.3×10−7M) and 1.5 to 2 fold greater increase in rate than that observed with unfractionated heparin. Under these conditions it could be calculated that the potency of a 32KDa fraction was 1200iu/mg with respect to UF heparin (150iu/mg). Three further pools were prepared and ATIII .high affinity fraction prepared by chromatography. Acceleration of rate of interaction was measured according to concentration and inverse plots gave values for apparent Kd amd maximal rate.These results suggest that differences in the profiles of stimulation by high Mr fractions to those of lower Mr are related to higher binding affinities for the inhibitor permitting maximal binding of heparin before the descending part of the slope due to saturation of thrombin (according to the template hypothesis). Although close similarity was found between heparin stimulation of HCII and ATIII, potentiation of HCII inhibitory activity differed in that it was reversed by lower ionic strength and was not reversed by a heparin pentasaccharide with high affinity for ATIII.

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