scholarly journals Kinetics of the reaction of streptokinase-plasmin complex with purified human and mouse α2-macroglobulin. Implications for mechanism

1989 ◽  
Vol 264 (3) ◽  
pp. 745-752 ◽  
Author(s):  
P K Anonick ◽  
W H Vetter ◽  
S L Gonias
Keyword(s):  
Order Rate Constant ◽  
Direct Reaction ◽  
Major Mechanism ◽  
Order Rate ◽  
Α2 Macroglobulin ◽  
Rate Of Reaction ◽  
Fibrinogenolytic Activity ◽  
Kinetics Of ◽  
Human And Mouse

Streptokinase-human plasmin complex (Sk-hPm) reacted rapidly with purified mouse alpha 2-macroglobulin (m alpha 2M) in vitro at 37 degrees C. Approx. 98% of the plasmin in Sk-hPm bound covalently to at least one m alpha 2M subunit. Most of the streptokinase dissociated (95%). The rate of Sk-hPm inactivation clearly depended on the m alpha 2M concentration. With 1.2 microM-m alpha 2M, 50% of the Sk-hPm (0.02 microM) reacted in less than 50 s. A double-reciprocal plot comparing pseudo-first-order rate constants (kapp.) and m alpha 2M concentration yielded a second-order rate constant of 2.3 x 10(4) M-1.s-1 (r = 0.97). This value is an approximation, since Sk-hPm preparations are heterogeneous. Sk-hPm reacted with human alpha 2M (h alpha 2M), forming alpha 2M-plasmin complex (98% covalent). More than 99% of the streptokinase dissociated. The rate of reaction of Sk-hPm with h alpha 2M did not clearly depend on inhibitor concentration. The kapp. values determined with 0.6-1.2 microM-h alpha 2M were decreased 10-20-fold compared with m alpha 2M. In order to study the effect of Sk-hPm heterogeneity on the reaction with alpha 2M, the proteinase was incubated for various amounts of time at 37 degrees C before addition of inhibitor. The enzyme amidase activity was maximal within 5 min; however, reaction of Sk-hPm with m alpha 2M or h alpha 2M was most extensive after 20 min and 2 h respectively. After incubation for more than 1 h, Sk-hPm acquired fibrinogenolytic activity, suggesting plasmin dissociation. Therefore the enhanced reaction of h alpha 2M with ‘older’ Sk-hPm preparations may have resulted in part from dissociated plasmin or ‘plasmin-like’ species. By contrast, the reaction of Sk-hPm with m alpha 2M was most rapid when the proteinase preparation was free of plasmin, indicating direct reaction of Sk-hPm with m alpha 2M as the only major mechanism. Finally, streptokinase-cat plasminogen complex reacted more extensively with m alpha 2M than with h alpha 2M, suggesting that m alpha 2M may be a superior inhibitor with this class of plasminogen activators in general.

scholarly journals Compounds of 6, 13-Diamino-6, 13-Dimethyl-1, 4, 8, 11 - Tetraazacyclotetradecane

2021 ◽  
Author(s):  
◽  
Asokamali Siriwardena
Keyword(s):  
Rate Constants ◽  
Magnetic Measurements ◽  
Order Rate Constant ◽  
Acidic Solutions ◽  
First Order ◽  
Order Rate ◽  
Pendant Arm ◽  
Nickel Copper ◽  
13C Nuclear Magnetic Resonance ◽  
Kinetics Of

<p>The reaction of bis-(diaminoethane)nickel(II) chloride, ([Ni(en)2]Cl2 in methanol with formaldehyde and nitroethane in the presence of triethylamine proceeds readily to produce (6, 13-dimethyl-6, 13-dinitro-1, 4, 8, 11-tetraazacyclotetradecane)nickel(II) chloride, [Ni(dini)] - Cl2. Reduction of the nitro groups of this compound by catalytic hydrogenation yields three isomers of the pendant arm macrocyclic complex (6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazachyclotetradecane)nickel(II) chloride, designated a-, b- and c-[Ni(diam)]Cl2. These were separated by fractional crystallization. The aisomer was observed to isomerizes slowly in solution to the b- form. A parallel dissociation reaction of the a- isomer was also observed. The demetallation of a- and b- isomers of the diam complex of nickel by reaction with cyanide or concentrated acid at 140 degrees C produces the macrocycle meso-(6, 13-diamino-6, 13-dimethyl-1, 4, 8, 11-tetraazacyclotetra-decane), diam. A variety of hexamine, pentamine and tetramine complexes of diam with nickel(II), copper(II), cobalt(II) and (III), chromium(III), palladium(II), rhodium(III), zinc(II) and cadmium(II) were prepared. Hexamine and tetramine forms of labile metal complexes could be rapidly and reversibly interconverted by altering the pH. The hexamine cobalt(III) cation, [Co(diam)]3+ was by far the most inert of the prepared cobalt(III) complexes, remaining unaffected in hot acidic solutions. In contrast, a single pendant arm of the hexamine [Cr(diam)]3+ cation could be dissociated in acid. (Two possibly triamine complexes of lead were also prepared). These compounds were characterized by elemental analysis, magnetic measurements, electronic, infrared, 1H and 13C nuclear magnetic resonance spectra. The pendant arm protonation constants (log K) of diam and selected complexes of nickel, copper and palladium were calculated from potentiometric titration measurements at 25 degrees C. The log K values for diam at 25 degrees C (I = 0.1 M NaclO4) were 11.15, 9.7, 6.2 and 5.3. Kinetics of the parallel isomerization and dissociation of a-[Ni(dimH2)]4+ in HCl/NaCl solutions were monitored spectrophotometrically at 50 degrees C. The rate of reaction in acidic solutions showed a non-linear dependency on acid concentration. The observed first order rate constant (kobs) for disappearance of a-[Ni(diamH2)]4+ (by isomerization and dissociation) in 2.0 M HCl, 0.1 M NaOH and 2.0 M NaCl were 3.05 x 10-4, 2.0(3) x 10-2 and 5.0 x 10-5 s-1 respectively. The rate of the dissociation component of the reaction of a-[Ni(diamH2)]4+ in 2.0 M HCl at 50 degrees C was 1.82 x 10-7 s-1. Acid bydrolysis kinetics of (Cu[diamH2])(ClO4)4 in hydrochloric acid and perchloric acid at 50 and 70 degrees C were studied spectrophotometrically. The reactions were slow and the observed first order rate constants were to a first approximation independent of the particular acid or its concentration. The observed first order rate constants were 1 x 10-9 and 8 x 10-9 s-1 at 50 and 70 degrees C respectively. Questions about the nature of the reaction being followed have been raised.</p>

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.

Quantitative Determination of Total Antithrombin III in Plasma

1973 ◽  
Vol 30 (01) ◽  
pp. 084-092 ◽  
Author(s):  
Robert H. Yue ◽  
Toby Starr ◽  
Menard M. Gertler
Keyword(s):  
Antithrombin Iii ◽  
Order Rate Constant ◽  
Graphical Analysis ◽  
Least Square ◽  
Assay System ◽  
Simple Method ◽  
Order Rate ◽  
Straight Line ◽  
Α2 Macroglobulin

SummaryA relatively simple method has been developed to evaluate the total amount of antithrombin III in plasma. Since purified and stable bovine thrombin was readily prepared in our laboratory, it was selected to be used in our assay system. Purified α2-macroglobulin was found to inactivate thrombin following a pseudo first-order rate of reaction. However, purified antithrombin III inactivated thrombin following a bimolecular type of reaction. The second-order rate constant for antithrombin III and thrombin interaction was found to be 94 1/M/sec. under these conditions. A least-square straight line was drawn between 15 and 90 minute intervals and the intercept yielded the total amount of antithrombin III expressed NIH thrombin units. This assay system and the graphical analysis yielded the total amount of antithrombin III in plasma quantitatively. The results are reproducible.

scholarly journals Acid Hydrolysis of Bis(2,2'; 6',2''–Terpyridyl) Iron(II) Complex in the Water Pools of CTAB/Hexane/Chloroform Reverse Micelles-A Kinetic Study in Confined Medium

2020 ◽  
Vol 15 (3) ◽  
pp. 853-860
Author(s):  
K. V. Nagalakshmi ◽  
P. Shyamala
Keyword(s):  
Ionic Strength ◽  
Acid Hydrolysis ◽  
Reverse Micelles ◽  
Order Rate Constant ◽  
Micellar Medium ◽  
First Order ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of acid hydrolysis of bis(2,2';6',2''–terpyridyl) iron(II) complex has been studied in CTAB/Hexane/Chloroform reverse micelles. The reaction obeys first order kinetics with respect to each of the reactants at all values of W, {W= [H2O]/[CTAB]}. In the reverse micellar medium, the reaction is much slower compared to aqueous medium due to low micropolarity of the water pools which does not facilitate a reaction between reactants of same charge. The effect of variation of W {W=[H2O]/[CTAB]} at constant [CTAB] and variation of [CTAB] at fixed W has been studied. The second order rate constant (k2) of the reaction increases as the value of W increases up to W = 8.88 and remains constant thereafter and it is independent of concentration of [CTAB] at constant W. The variation of rate of reaction with W has been explained by considering variation of micropolarity and ionic strength of water pools of reverse micelles with W. Copyright © 2020 BCREC Group. All rights reserved 

Kinetics of Reactions of 8-Quinolinol and Acetate with Hydroxyaluminum Species in Aqueous Solutions. 1. Polynuclear Hydroxyaluminum Cations

1971 ◽  
Vol 49 (10) ◽  
pp. 1683-1687 ◽  
Author(s):  
R. C. Turner ◽  
Wan Sulaiman
Keyword(s):  
Acetic Acid ◽  
Rate Constant ◽  
Empirical Equation ◽  
Decomposition Reaction ◽  
Order Rate Constant ◽  
Acetate Concentration ◽  
First Order ◽  
Order Rate ◽  
Pseudo First Order ◽  
Kinetics Of

The effect of varying 8-quinolinol and acetate concentration on the rate of decomposition of poly-nuclear hydroxyaluminum cations was studied. It was found that the concentration of the undissociated 8-quinolinol and acetic acid molecules determined the magnitude of the first order rate constant for the decomposition of the polynuclear hydroxyaluminum cations, except when the acetate concentrations were relatively high. With high acetate concentrations, it appeared that polynuclear acetate species were involved in the reactions. An empirical equation was developed showing the effect of 8-quinolinol and acetic acid molecule concentrations on the pseudo first order rate constant for the decomposition reaction.

Studies on Horseradish Peroxidase. XI. On the Nature of Compounds I and II as Determined from the Kinetics of the Oxidation of Ferrocyanide

1973 ◽  
Vol 51 (4) ◽  
pp. 582-587 ◽  
Author(s):  
M. L. Cotton ◽  
H. B. Dunford
Keyword(s):  
Horseradish Peroxidase ◽  
Rate Constant ◽  
Active Sites ◽  
Ph Dependence ◽  
Order Rate Constant ◽  
Second Order ◽  
Compound I ◽  
Order Rate ◽  
Compound Ii ◽  
Kinetics Of

In order to investigate the nature of compounds I and II of horseradish peroxidase, the kinetics were studied of ferrocyanide oxidation catalyzed by these compounds which were prepared from three different oxidizing agents. The pH dependence of the apparent second-order rate constant for ferrocyanide oxidation by compound I, prepared from ethyl hydroperoxide and m-chloroperbenzoic acid, was interpreted in terms of an ionization on the enzyme with a pKa = 5.3, identical to that reported previously for hydrogen peroxide. The second-order rate constant for the compound II-ferrocyanide reaction also showed the same pH dependence for the three oxidizing substrates. However, with more accurate results, the compound II-ferrocyanide reaction was reinterpreted in terms of a single ionization with pKa = 8.5. The same dependence of ferrocyanide oxidation on pH suggests structurally identical active sites for compounds I and II prepared from the three different oxidizing substrates.

Kinetics of glycoluril template-directed Claisen condensations and mechanistic implications

2002 ◽  
Vol 80 (5) ◽  
pp. 517-527 ◽  
Author(s):  
Mohammad Rahimizadeh ◽  
Karen Kam ◽  
Stephen I Jenkins ◽  
Robert S McDonald ◽  
Paul HM Harrison
Keyword(s):  
Uv Spectroscopy ◽  
Condensation Reaction ◽  
Order Rate Constant ◽  
Nucleophilic Attack ◽  
First Order ◽  
Order Rate ◽  
First Order Kinetics ◽  
Benzoyl Group ◽  
Excess Base ◽  
Kinetics Of

Eight N-acetyl-N-aroyl-glycolurils were prepared and found to undergo efficient tert-butoxide-promoted Claisen-like condensation between the two acyl moieties. The kinetics for formation of each of the N-(aroylacetyl)gly coluril products were monitored by UV spectroscopy. The reaction exhibited pseudo-first-order kinetics in substrate in the presence of excess base. For the parent benzoyl compound the observed first-order rate constant (kobs) was linearly dependent on the concentration of the base, tert-butoxide. A Hammett plot of the resulting apparent second-order rate constants (kapp) vs. σ for each of the eight aroyl derivatives was linear and had a positive ρ value 1.04 ± 0.04), demonstrating that the substituent on the aromatic ring exerts a significant effect upon the condensation reaction. The corresponding plot for three [D3]acetyl analogues was also linear, but the slope was reduced by 20% relative to the protonated compounds. The isotope effect (kHapp/kDapp) thus increased from 1.4 (benzoyl) to 2.6 (p-nitrobenzoyl). The results are consistent with a three-step mechanism in which both deprotonation of the acetyl entity and the ensuing nucleophilic attack of the resulting enolate on the benzoyl group are partially rate-determining steps. The tetrahedral intermediate thus produced rapidly collapses to the product. For the [D3]acetyl benzoyl derivative, exchange of substrate deuterium with solvent hydrogen due to reprotonation of the enolate intermediate occurs at a rate that is similar to that of condensation, but the enolate partitions towards the product when electron withdrawing groups are present in the aroyl ring. Thus, despite the presence of a large excess of co-solvent tert-butanol, the efficiency with which the enolate undergoes condensation remains high. The clean kinetics observed allows further exploration of the details of this intramolecular Claisen-like condensation process.Key words: Claisen condensation, glycoluril, kinetics, Hammett, mechanism.

scholarly journals Effect of A(n) tracts within the UP element proximal subsite of a model promoter on kinetics of open complex formation by Escherichia coli RNA polymerase.

2002 ◽  
Vol 49 (3) ◽  
pp. 659-669 ◽  
Author(s):  
Iwona K Kolasa ◽  
Tomasz Loziński ◽  
Kazimierz L Wierzchowski
Keyword(s):  
Escherichia Coli ◽  
Rna Polymerase ◽  
Promoter Region ◽  
Dna Bending ◽  
Proximal Part ◽  
Order Rate Constant ◽  
Order Of Magnitude ◽  
Sigma 70 ◽  
Kinetics Of

In the open transcription complex (RPo), Escherichia coli RNA polymerase sigma(70) and alpha subunits are known to be in contact with each other and with the promoter region overlapping the -35 hexamer and the proximal part of the UP element. To probe the effect of A(n) DNA bending tracts in this region on initiation of transcription, kinetics of the formation of RPo by Escherichia coli RNA polymerase at two groups of synthetic consensus-like promoters bearing single DNA bending tracts (i). A(5 )within the proximal subsite region of the UP element (promoters Pk and Pl) and (ii). A(5)(Pg) or A(8)(Pm) in the region including the downstream end of the proximal UP subsite and the -35 consensus hexamer was studied in vitro using the fluorescence-detected abortive initiation assay. The kinetic data obtained demonstrate that the overall second-order rate constant k(a) of RPo formation is: (i.by almost one order of magnitude larger at Pk and Pl, relative to that at a control unbent promoter, and mainly due to a higher value of the equilibrium constant, K(1), of the initial closed complex; and (ii). several-fold smaller at Pg and Pm owing to a strongly decreased value of K(1). For Pm, the latter parameter was found to be dependent exponentially on four Mg(2+) ions, as compared with the seven ions remaining in equilibrium with the initial closed complex at the parent Pa promoter. This indicates that promoter region bearing a stiff A(8).T(8) fragment of B -DNA forms a smaller number of ionic contacts with the alpha subunit. These findings provide a new insight to and support the present model of interactions between RNA polymerase alpha and sigma(70) subunits with the proximal UP subsite and the -35 region of promoters.

Kinetics of Exchange of Dimethylsulfoxide between Hexakis(dimethylsulfoxide)chromium(III) and Solvent: Pressure Effect and Mechanism

1973 ◽  
Vol 51 (22) ◽  
pp. 3795-3798 ◽  
Author(s):  
Debra Lynn Carle ◽  
Thomas Wilson Swaddle
Keyword(s):  
Rate Constant ◽  
Pressure Effect ◽  
Order Rate Constant ◽  
First Order ◽  
Order Rate ◽  
Kinetics Of

For the exchange of all six dimethylsulfoxide (DMSO) ligands in Cr(DMSO)63+ with perdeuterated DMSO solvent, the first-order rate constant (75°) = 5.5 × 10−5 s−1, while ΔH* = 23.1 kcal mol−1, ΔS* = − 11.8 cal deg−1 mol−1, and ΔV* = − 11.3 cm3 mol−1. These and other data are indicative of an associative interchange mechanism for substitution in Cr(III) DMSO complexes in DMSO.

Oxidation of the mercurous ion by peroxidase

1986 ◽  
Vol 64 (5) ◽  
pp. 969-972 ◽  
Author(s):  
Donald C. Wigfield ◽  
Season Tse
Keyword(s):  
Elemental Mercury ◽  
Order Rate Constant ◽  
Kinetics Of Oxidation ◽  
First Order ◽  
Order Rate ◽  
First Order Kinetics ◽  
Cold Vapour ◽  
Pseudo First Order ◽  
Kinetics Of ◽  
Mercurous Ion

The kinetics of oxidation of the mercurous ion by peroxidase have been measured by following the disappearance of mercurous ion using cold-vapour atomic absorption spectroscopy. Pseudo-first-order kinetics are observed with respect to mercurous ion, and the pseudo-first-order rate constants are linearly related to peroxidase concentration, showing first-order dependence on peroxidase. This behaviour is identical to oxidation of elemental mercury, and the second-order rate constant, 1.44 × 104 M−1 s−1 at 23 °C, is also, within experimental error, the same as that for elemental mercury oxidation. The data are interpreted in terms of peroxidase-induced disproportionation of the mercurous dimer, followed by two-electron oxidation of zero-valent mercury.

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