Heparin Effects (And Mechanisms) In The α2-Antithrombin Inactivation Of Serine Proteases--Thrombin, Plasmin, And Trypsin

1981 ◽  
Author(s):  
Gerald F Smith ◽  
Jacqueline L Sundboom
Keyword(s):  
Serine Proteases ◽  
Physiological Role ◽  
Binding Constants ◽  
Reaction Rates ◽  
Heparin Therapy ◽  
Common Mechanism ◽  
High Concentration ◽  
Protein Substrates ◽  
Kinetics Of ◽  
Very High

It is important to elucidate the effects of heparin on the α2-antithrombin (ATIII) inactivation of serine proteases in order to understand the pharmacological activity of heparin. We have studied the enzyme kinetics of the ATIII inactivation of these proteases, and the effects of heparin on these interactions, using a common amide peptide substrate and protein substrates. We also studied the interactions of heparin with the three proteases.We conclude that the mechanism of the catalytic effect of heparin (observed at 0. 005 unit/ml) toward the thrombin- ATIII reaction is different from the mechanism whereby heparin (only at very high concentration, e.g., 10 unit/ml) can induce an enhanced rate in the plasmin-ATIII reaction. We conclude that the first mechanism involves a heparinthrombin complex, while the mechanism with plasmin involves a heparin-ATIII complex which forms only at high heparin concentrations. This is consistent with known appropriate binding constants. We found that heparin has no effect on the very rapid inactivation of trypsin by ATIII. We further conclude that there is no common mechanism whereby clinically relevant levels of heparin cause general enhanced ATIII-protease reaction rates.We suggest ATIII depletion during heparin therapy might be avoided by using low heparin levels, which would not allow heparin-ATIII complexes to form, yet which would catalyze the thrombin-ATIII reaction. Our finding that ATIII inactivates trypsin at a rate similar to the heparin-catalyzed thrombin-ATIII reaction suggests a physiological role for ATIII in the control of trypsin-like enzymes.

scholarly journals Kinetics of saccharose fermentation by Kombucha

2014 ◽  
Vol 20 (3) ◽  
pp. 345-352 ◽  
Author(s):  
Eva Loncar ◽  
Katarina Kanuric ◽  
Radomir Malbasa ◽  
Mirjana Djuric ◽  
Spasenija Milanovic
Keyword(s):  
Empirical Model ◽  
Black Tea ◽  
Reaction Rates ◽  
Yeast Cells ◽  
Inoculum Concentration ◽  
Viable Cells ◽  
Rate Of Reaction ◽  
Kinetics Of ◽  
Derivatives Of ◽  
Very High

Kinetics of saccharose fermentation by Kombucha is not yet well defined due to lack of knowledge of reaction mechanisms taking place during this process. In this research kinetics of saccharose fermentation by Kombucha was analysed using the suggested empirical model. The data were obtained on 1.5 g L-1 of black tea, with 66.47 g L-1 of saccharose and using 10% (v/v) or 15% (v/v) of Kombucha. Total number of viable cells was as follows: approximately 5x105 of yeast cells per mL of the inoculum and approximately 2x106 of bacteria cells per mL of the inoculum. The samples were analysed after 0, 3, 4, 5, 6, 7 and 10 days. Their pH values and contents of saccharose, glucose, fructose, total acids and ethanol were determined. A saccharose concentration model was defined as sigmoidal function at 22oC and 30oC, and with 10% (v/v) and 15% (v/v) of inoculum quantity. Determination coefficients of the functions were very high (R2>0.99). Reaction rates were calculated as first derivatives of Boltzmann?s functions. No simple correlation between rate of reaction and independent variables (temperature and inoculum concentration) was found. Analysis of empirical model indicated that saccharose fermentation by Kombucha occurred according to very complex kinetics.

scholarly journals Kinetics of Reduction of Colloidal MnO2 by Glyphosate in Aqueous and Micellar Media

2011 ◽  
Vol 2011 ◽  
pp. 1-6 ◽  
Author(s):  
Uzma Aisha ◽  
Qamruzzaman ◽  
M. Z. A. Rafiquee
Keyword(s):  
Cetyltrimethylammonium Bromide ◽  
Binding Constants ◽  
Reaction Rates ◽  
Lauryl Sulfate ◽  
Micellar Media ◽  
First Order Kinetics ◽  
Rate Of Reaction ◽  
Colloidal Mno2 ◽  
Kinetics Of ◽  
Kinetics Of Reduction

The kinetics of the reduction of colloidal MnO2 by glyphosate has been investigated spectrophotometrically in an aqueous and micellar (cetyltrimethylammonium bromide, sodium lauryl sulfate) media. The reaction follows first-order kinetics with respect to colloidal MnO2 in both the aqueous and micellar media. The rate of oxidation increases with increase in [glyphosate] in the lower concentration range but becomes independent at its higher concentrations. The addition of both the anionic (NaLS) and cationic (CTAB) micelles increased the rate of reduction of colloidal MnO2 by glyphosate while the nonionic TX-100 micelles did not influence the rate of reaction. In both aqueous and micellar media, the oxidation of glyphosate occurs through its adsorption over colloidal MnO2 surface. The reaction in micellar media was treated by considering the pseudophase model. The values of reaction rates and binding constants in the presence of micelles were determined.

Effect of short-chained sodium alkylsulfate micelles on the kinetics of metal complex formation

1981 ◽  
Vol 59 (9) ◽  
pp. 1361-1367 ◽  
Author(s):  
Paul D. I. Fletcher ◽  
Vincent C. Reinsborough
Keyword(s):  
Alkyl Chain ◽  
Binding Constants ◽  
Micelle Formation ◽  
Reaction Rates ◽  
Bidentate Ligand ◽  
Alkyl Chain Length ◽  
Stopped Flow ◽  
Micellar Solutions ◽  
Kinetics Of ◽  
Micelle Surface

The kinetics of the reaction between Niaq2+ and the bidentate ligand pyridine-2-azo-p-dimethylaniline (PADA) have been investigated in micellar solutions of sodium decyl-, octyl-, and hexylsulfates using the stopped-flow technique. The rate of enhancement decreased with decreasing alkyl-chain length and from the Berezin or Robinson model could be quantitatively related to the independently measured binding constants of Ni2+ ion and PADA to the micelle surface. The dramatic effect of micelles upon the reaction rates in different directions of the Ni2+/PADA and the Ni2+/murexide reactions served as sensitive indicators of the cmc even at the very limit of micelle formation which relatively concentrated sodium hexylsulfate solutions represent.

scholarly journals THE KINETICS OF THE DECOMPOSITION OF PEROXIDE BY CATALASE

1925 ◽  
Vol 7 (3) ◽  
pp. 373-387 ◽  
Author(s):  
John H. Northrop
Keyword(s):  
Hydrogen Peroxide ◽  
Experimental Results ◽  
Inactivation Rate ◽  
High Concentration ◽  
Inactivation Constant ◽  
Monomolecular Decomposition ◽  
High Concentrations ◽  
Kinetics Of ◽  
Very High

It has been shown that the experimental results obtained by Morgulis in a study of the decomposition of hydrogen peroxide by liver catalase at 20°C. and in the presence of an excess of a relatively high concentration of peroxide are quantitatively accounted for by the following mechanisms. 1. The rate of formation of oxygen is independent of the peroxide concentration provided this is greater than about 0.10 M. 2. The rate of decomposition of the peroxide is proportional at any time to the concentration of catalase present. 3. The catalase undergoes spontaneous monomolecular decomposition during the reaction. This inactivation is independent of the concentration of catalase and inversely proportional to the original concentration of peroxide up to 0.4 M. In very high concentrations of peroxide the inactivation rate increases. 4. The following equation can be derived from the above assumptions and has been found to fit the experiments accurately. See PDF for Equation in which x is the amount of oxygen liberated at the time t, A is the total amount of oxygen liberated (not the total amount available), and K is the inactivation constant of the enzyme.

m-[o-(2-Chloro-5-Fluorosulfonylphenylureido)Phenoxybutoxy]Benzamidine: Affinity Labeling Reagent Which Can Identify Secondary Binding Sites of Coagulation Complement and Fibrinolytic Serine Proteases

1979 ◽  
Author(s):  
D Bing ◽  
D Robison ◽  
J Andrews ◽  
R Laura
Keyword(s):  
Binding Sites ◽  
Serine Proteases ◽  
Enzyme Inhibitor ◽  
Molecular Model ◽  
Factor Xa ◽  
Affinity Labeling ◽  
Catalytic Center ◽  
Inhibitor Complex ◽  
Polypeptide Chains ◽  
Kinetics Of

We have determined that m-[o-(2-chloro-5-fluorosulfonylphenylureido)phenoxybutoxy]benza-midine [mCP(PBA)-F] is an affinity labeling reagent which labels both polypeptide chains of thrombin, factor Xa, complement component CIS and plasmin. As this means it is reacting outside of the catalytic center, we have called this reagent an exo-site affinity labeling reagent. Progressive irreversible inhibition of these enzymes by this reagent is rapid (k1st 2.5-4.6 x 10-3sec-1), the kinetics of inactivation are consistent with inhibition proceding via formation of a specific enzyme-inhibitor complex analogous to a Michaelis-Menton complex (KL - 115-26 μM), and diisopropylfluorophosphate or p-amidino-phenylmethanesulfonyfluoride Prevent labeling by [3H]mCP(PBA)-F. A molecular model of mCP(PBA)-F shows that the reactive SO2F group can be 17 A from the cationic amidine. The data are consistent with the hypothesis that both peptide chains are required for the specific proteolytic activity exhibited by these proteases and that the peptide chain which does not contain the active site serine is close to the catalytic center. (Supported by NIH and AHA grants

Ground water quality of selected areas of Punjab and Sind Provinces, Pakistan: Chemical and microbiological aspects

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Ionic Concentration ◽  
Chloride Ions ◽  
Potassium Ions ◽  
Ammonium Ions ◽  
High Concentration ◽  
Phosphate Ions ◽  
Sodium Magnesium ◽  
Very High ◽  
Microbiological Aspects

The assessment of groundwater is essential for the estimation of suitability of water for safe use. An attempt has been made to study the groundwater of selected areas of Punjab (Sheikhupura & Sahiwal) and Sindh (Sindh, Jawar Dharki and Dharki), Pakistan. The results indicate that pH, color and odor were all within limits of WHO that is pH ranges 6.5–8.5, colorless and odorless, respectively. The high values of suspended solids were observed in the Sindh-1 and Dharki samples. Microbiologically only Sahiwal and Jawar Dharki were found fit for drinking purpose. Trace metals analysis of Sheikhupura-1 and Sindh-1 showed that values do not fall within limits of WHO for Iron. The ionic concentration analysis showed that high bicarbonate (HCO3-), ions are present in the samples of Sahiwal and Dharki; Sindh-1 and Jawar Dharki samples showed very high concentration for chloride ions, all samples were satisfactory level for sulphate (SO42-), sodium, magnesium and phosphate ions except samples of Sindh-1 and Jawar Dharki. High concentration of calcium and potassium ions was observed in samples of Sindh-1, while all other samples were found fit for drinking purposes in respect of nitrate, nitrite and ammonium ions. The high concentration of Fluoride was found only in Sheikhupura-2 samples.

The effect of heterotrophic yield on the assessment of the correction factor for anoxic growth

1996 ◽  
Vol 34 (5-6) ◽  
pp. 67-74 ◽  
Author(s):  
D. Orhon ◽  
S. Sözen ◽  
N. Artan
Keyword(s):  
Correction Factor ◽  
Domestic Sewage ◽  
Yield Coefficient ◽  
Heterotrophic Growth ◽  
Metabolic Processes ◽  
Anoxic Conditions ◽  
Industrial Wastewaters ◽  
Systems Modelling ◽  
Kinetics Of ◽  
Very High

For single-sludge denitrification systems, modelling of anoxic reactors currently uses the kinetics of aerobic heterotrophic growth together with a correction factor for anoxic conditions. This coefficient is computed on the basis of respirometric measurements with the assumption that the heterotrophic yield remains the same under aerobic and anoxic coditions. The paper provides the conceptual proof that the yield coefficient is significantly lower for the anoxic growth on the basis of the energetics of the related metabolic processes. This is used for the interpretation of the very high values for the correction factor experimentally determined for a number of industrial wastewaters. A default value for the anoxic heterotrophic yield coefficient is calculated for domestic sewage and compatible wastewaters and proposed for similar evaluations.

Kinetics of esterification of monoisopropylphenols with phosphoryl trichloride

1989 ◽  
Vol 54 (5) ◽  
pp. 1311-1317
Author(s):  
Miroslav Magura ◽  
Ján Vojtko ◽  
Ján Ilavský
Keyword(s):  
Liquid Phase ◽  
Rate Constants ◽  
Reaction Rates ◽  
Activation Energies ◽  
The Individual ◽  
Kinetics Of

The kinetics of liquid-phase isothermal esterification of POCl3 with 2-isopropylphenol and 4-isopropylphenol have been studied within the temperature intervals of 110 to 130 and 90 to 110 °C, respectively. The rate constants and activation energies of the individual steps of this three-step reaction have been calculated from the values measured. The reaction rates of the two isomers markedly differ: at 110 °C 4-isopropylphenol reacts faster by the factors of about 7 and 20 for k1 and k3, respectively. This finding can be utilized in preparation of mixed triaryl phosphates, since the alkylation mixture after reaction of phenol with propene contains an excess of 2-isopropylphenol over 4-isopropylphenol.

Vancomycin Adsorption During in vitro Model of Hemoperfusion with HA380 Cartridge

Nephron ◽  
2021 ◽  
pp. 1-7
Author(s):  
Ilaria Godi ◽  
Anna Lorenzin ◽  
Silvia De Rosa ◽  
Gianlorenzo Golino ◽  
Maira Knust ◽  
...  
Keyword(s):  
Complete Removal ◽  
Potential Interaction ◽  
Blood Purification ◽  
Therapeutic Monitoring ◽  
High Concentration ◽  
Langmuir Isotherm Model ◽  
Vitro Model ◽  
Kinetics Of ◽  
Balanced Solution

<b><i>Introduction:</i></b> A critical point for using blood purification during sepsis may be the potential interaction with antimicrobial therapy, the mainstay of sepsis treatment. The aim of our study was to investigate the vancomycin removal during hemoperfusion (HP) using HA380 cartridge. <b><i>Methods:</i></b> This is an experimental study, in which 500 mL of solution was circulated in a closed-circuit (blood flow of 250 mL/min) simulating HP ran using HA380. Vancomycin was added to reach a through concentration or a very high concentration to evaluate the removal ratio (RR) during 120 min of HP. Comparison between blood-crystalloid solution and balanced solution was performed by using Kruskal-Wallis test. The kinetics of vancomycin removal and the adsorption isotherm were evaluated. <b><i>Results:</i></b> We found a complete removal of vancomycin at baseline through concentration of 23.0 ± 7.4 mg/L. Using extremely high concentration (baseline 777.0 ± 62.2 mg/L), RR was 90.1 ± 0.6% at 5 min and 99.2 ± 0.6% at 120 min. No difference in terms of RR was found between blood-crystalloid mixture and balanced solution. The kinetics of the vancomycin reduction followed an exponential decay. Repeated boluses (total amount of 2,000 mg) resulted in cumulative adsorption of 1,919.4 mg with RR of 96.6 ± 1.4%, regardless of the amount injected (100 vs. 500 mg). Vancomycin adsorption onto HA380 followed the Langmuir isotherm model. <b><i>Conclusions:</i></b> A considerable amount of vancomycin was rapidly removed during in vitro HP with HA380. Clinical studies are needed to determine whether this may lead to underdosing. Drug therapeutic monitoring is highly recommended when using HA380 for blood purification in patients receiving vancomycin.

scholarly journals Near quantitative synthesis of urea macrocycles enabled by bulky N-substituent

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Yingfeng Yang ◽  
Hanze Ying ◽  
Zhixia Li ◽  
Jiang Wang ◽  
Yingying Chen ◽  
...  
Keyword(s):  
High Efficiency ◽  
Molecular Structures ◽  
High Yield ◽  
Kinetic Control ◽  
High Concentration ◽  
Weak Association ◽  
Quantitative Synthesis ◽  
Thermodynamic Stabilization ◽  
Discrete Structures ◽  
Very High

AbstractMacrocycles are unique molecular structures extensively used in the design of catalysts, therapeutics and supramolecular assemblies. Among all reactions reported to date, systems that can produce macrocycles in high yield under high reaction concentrations are rare. Here we report the use of dynamic hindered urea bond (HUB) for the construction of urea macrocycles with very high efficiency. Mixing of equal molar diisocyanate and hindered diamine leads to formation of macrocycles with discrete structures in nearly quantitative yields under high concentration of reactants. The bulky N-tert-butyl plays key roles to facilitate the formation of macrocycles, providing not only the kinetic control due to the formation of the cyclization-promoting cis C = O/tert-butyl conformation, but also possibly the thermodynamic stabilization of macrocycles with weak association interactions. The bulky N-tert-butyl can be readily removed by acid to eliminate the dynamicity of HUB and stabilize the macrocycle structures.

Sign in / Sign up

Export Citation Format

Share Document