scholarly journals Effect of Ionic Strength on the Kinetics of Trypsin and Alpha Chymotrypsin

1961 ◽  
Vol 44 (6) ◽  
pp. 1103-1120 ◽  
Author(s):  
M. Castañeda-Agulló ◽  
Luz M. del Castillo ◽  
J. R. Whitaker ◽  
A. L. Tappel
Keyword(s):  
Ionic Strength ◽  
Reaction Rate ◽  
Inorganic Ions ◽  
Ion Association ◽  
Inhibitory Effect ◽  
Enzymatic Reactions ◽  
Kinetic Effects ◽  
Kinetics Of ◽  
Ionizable Groups ◽  
General Method

The kinetic effects resulting from changes in the medium ionic strength on reactions involving trypsin or α-chymotrypsin are different. The reaction rate increases continuously as the ionic strength increases with α-chymotrypsin. With trypsin, the rate increases at low ionic strengths but as the ionic strength further increases a gradual inhibitory effect is observed. The effects produced by different salts of various valence types (from uni-univalent to uni-trivalent or tri-univalent) are essentially the same, and they are a function of the square root of the ionic strength. The quantitative differences among the various salts may be accounted for on the basis of individual properties of the ions, such as the size of the hydrated ion, "association," etc. The effects of salts on the enzymic reactions described herein are amenable to the same electrostatic treatment applicable to non-enzymatic reactions. By applying Brönsted's basic kinetic concepts and the Debye-Hückel law of electrolyte activity, it appears that the salt effects are mainly due to changes in the dissociation of ionizable groups. This appears to be a general method for analyzing the effect of inorganic ions on enzymic reactions.

Kinetics of oxidation of cis-bis(ethylenediamine)isothiocyanatonitrocobalt(III) ion with peroxodisulphate

1979 ◽  
Vol 44 (12) ◽  
pp. 3588-3594 ◽  
Author(s):  
Vladislav Holba ◽  
Olga Volárová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Oxidation Kinetics ◽  
Reaction Rate ◽  
Salt Effect ◽  
Activation Parameters ◽  
Reaction Products ◽  
Kinetics Of Oxidation ◽  
Thermodynamic Activation Parameters ◽  
Kinetics Of

The oxidation kinetics of cis-bis(ethylenediamine)isothiocyanonitrocobalt(III) ion with peroxodisulphate was investigated in the medium of 0.01 M-HClO4 in dependence on the ionic strength and temperature and the reaction products were identified. Extrapolated values of thermodynamic activation parameters were determined from the temperature dependence of the rate constants extrapolated to zero ionic strength. The distance of the closest approach was estimated for the reacting ions by evaluating the primary salt effect. To elucidate the mechanism, the influence of the cyclic polyether 18-crown-6 on the reaction rate was followed.

Kinetics of oxidation of hypophosphitopentamminechromium(III) ion with periodate

1981 ◽  
Vol 46 (10) ◽  
pp. 2503-2508 ◽  
Author(s):  
Olga Volárová ◽  
Vladislav Holba
Keyword(s):  
Ionic Strength ◽  
Oxygen Atom ◽  
Perchloric Acid ◽  
Redox Reaction ◽  
Reaction Rate ◽  
Kinetics Of Oxidation ◽  
Kinetics Of

The kinetics of oxidation of hypophosphitopentamminechromium(III) ion with periodate was investigated as a function of the temperature, ionic strength, and concentration of perchloric acid. The reaction rate decreased with increasing ionic strength and concentration of perchloric acid. The redox reaction proper involving transfer of an oxygen atom is preceded by dissociation of hydrogen from the coordinated hypophosphite. The reactivity of the latter is compared with that of the free hypophosphite.

KINETIC EFFECTS OF HIGH MOLECULAR WEIGHT KININOGEN AND ZINC ON CONTACT ACTIVATION

1987 ◽  
Author(s):  
J D Shore ◽  
D E Day ◽  
S T Olson
Keyword(s):  
Molecular Weight ◽  
Ionic Strength ◽  
High Molecular Weight ◽  
Proper Function ◽  
Factor Xii ◽  
High Molecular Weight Kininogen ◽  
Contact Activation ◽  
Kinetic Effects ◽  
Activation Rates ◽  
Kinetics Of

Previous work in our laboratory showed that Zn2+ enhanced the rate of kallikrein generation by dextran sulfate (DxSO4) in dialyzed normal plasma, but not in Fitzgerald or Hageman prismas. This could be partially explained by a marked effect of Zn2+ on factor XII autoactivation, and our present work involves zinc effects on other reactions of contact activation. At physiological ionic strength (0.15 μ), the kcat/Km for Xlla activation of prekallikrein (PK) was 0.62 μM™1 s™1 which was increased to 4.35 μM™1 s™1 by the presence of 25μg/ml DxSO4. High molecular weight kininogen (HMK) at 40 nM further increased this to 10.8 μM™1 s™1 , and 5 ¼M Zn2+ had no effect. To determine whether these cofactors promote a surface-dependent activation of PK by XIIa under conditions which weaken the protein-surface interactions, the kinetics were examined at 0.3μ. At this ionic strength, kcat/Km was 0.18 μM™1 s™1 and was unchanged by 25μg/ml DxSO4. This was increased to .805 μM™1 s™1 by 150 nM HMK and further increased 10-fold to 8.35 μM™1 s™1 by 10 μM™1 Zn2+ . Qualitative results were obtained at 0.3 μ for the other reciprocal reaction, XII activation by kallikrein (K). To observe XII activation within 2 hours, both 10 μM Zn2+ and 25 μM HMK were essential, indicating that these cofactors have a very large enhancing effect on the kinetics of this reaction. Chromatography of HMWK on DxSO4-agarose ^ljiowed elution of the protein at 0.42 M NaCl in the absence of Zn2+ ,but at 0.88M in its presence, providing evidence that Zn+ markedly increases the affinity of HMK for DxSO4. Our results are consistent with the increased activation rates observed in the presence of Zn2+ and HMK due to enhanced binding affinity of the reacting proteins to surfaces. This is likely to be essential for proper function of the contact system in blood, where many other proteins compete for surface. Supported by USPHS grant HL-25670

scholarly journals Kinetics and mechanism of the oxidation of some substituted aldonitrones by quinolinium chlorochromate in aqueous DMF medium in the absence and presence of oxalic acid

2009 ◽  
Vol 74 (2) ◽  
pp. 171-182 ◽  
Author(s):  
Govindasamy Rajarajan ◽  
Natesan Jayachandramani ◽  
Subramanian Manivarman ◽  
Jayaraman Jayabharathi ◽  
Venugopal Thanikachalam
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Oxalic Acid ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Experimental Conditions ◽  
First Order ◽  
Discernible Effect ◽  
Reactive Oxidant ◽  
Kinetics Of

The kinetics of the oxidation of aldonitrones (nitrone) by quinolinium chlorochromate (QCC) was determined in 50 % DMF-water in the absence and presence of oxalic acid in order to study the effect of oxalic acid. It was considered worthwhile to investigate whether it undergoes co-oxidation or just functions as a catalyst in the reaction. The reaction was followed iodometrically. Under the employed experimental conditions, the reaction is first order each with respect to concentration of nitrone, QCC, and oxalic acid and fractional order with respect to H+ concentration. There was no discernible effect with increasing in ionic strength but the rate of oxidation decreased with decreasing dielectric constant of the medium. Addition of MnSO4 had a significant and acrylonitrile no effect on the reaction rate. A mechanism involving protonated nitrone and QCC as the reactive oxidant is proposed. The activation parameters were calculated and are presented.

scholarly journals Oxidation of Chalcones by Morpholinium Chlorochromate with Oxalic Acid as Catalyst: Kinetic and Mechanistic Study

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
K. Rajalakshmi ◽  
T. Ramachandramoorthy
Keyword(s):  
Acetic Acid ◽  
Ionic Strength ◽  
Kinetic Data ◽  
Reaction Rate ◽  
Activation Parameters ◽  
Mechanistic Study ◽  
Kinetics Of Oxidation ◽  
Unit Order ◽  
Acetic Acid Water ◽  
Kinetics Of

The kinetics of oxidation of chalcones by morpholinium chlorochromate (MCC) has been studied in 55% acetic acid-water (v/v) medium. The reaction showed unit order dependence each with respect to oxidant and catalyst and fractional order with respect to substrate and H+ion. Increased ionic strength has no effect on the reaction rate. In the case of substituted chalcones, the order with respect to substrate varies depending upon the nature of the substituent present in the ring. In general, the electron withdrawing substituents retard the reaction rate while the electron releasing substituents enhance the rate of the reaction. From the kinetic data obtained, the activation parameters have been calculated and a suitable mechanism has been proposed.

STUDYING THE KINETIC CHARACTERISTICS OF THE EXTRACTION OF ANTHOCYANINS FROM THE SQUEEZE OF KRASNOSTOP ZOLOTOVSKY

2020 ◽  
Author(s):  
M.A. Egyan ◽  
Keyword(s):  
Reaction Rate ◽  
Sugar Content ◽  
Extraction Process ◽  
Efficiency Coefficient ◽  
Kinetic Characteristics ◽  
Reaction Rate Constants ◽  
Solids Content ◽  
Kinetics Of ◽  
Process Speed

The article shows studies characterizing the quality of the squeeze: the mechanical composition of the squeeze is determined, the structural moisture of each component is determined, the sugar content in the formed process of sedimentation of the juice and its acidity are determined refractometrically. The kinetics of anthocyanins extraction was determined in two ways, the solids content in the extract was calculated, and the reaction rate constants of the extraction process and the efficiency coefficient of ultrasonic amplification of the extraction process speed were calculated.

Thermal Decomposition Kinetics of Glyphosate (GP) and its Metabolite Aminomethylphosphonic Acid (AMPA)

2019 ◽  
Author(s):  
Milad Narimani ◽  
Gabriel da Silva
Keyword(s):  
Thermal Decomposition ◽  
Reaction Rate ◽  
Decomposition Kinetics ◽  
Rate Theory ◽  
Thermal Decomposition Mechanism ◽  
Treatment Processes ◽  
Aminomethylphosphonic Acid ◽  
Reaction Rate Theory ◽  
Decomposition Chemistry ◽  
Kinetics Of

Glyphosate (GP) is a widely used herbicide worldwide, yet accumulation of GP and its main byproduct, aminomethylphosphonic acid (AMPA), in soil and water has raised concerns about its potential effects to human health. Thermal treatment processes are one option for decontaminating material containing GP and AMPA, yet the thermal decomposition chemistry of these compounds remains poorly understood. Here, we have revealed the thermal decomposition mechanism of GP and AMPA by applying computational chemistry and reaction rate theory methods. <br>

Study of the Cu(II) removal from aqueous solutions by adsorption on titania

2013 ◽  
Vol 12 (3) ◽  
pp. 239-247
Keyword(s):  
Heavy Metals ◽  
Ionic Strength ◽  
Toxic Metals ◽  
Low Cost ◽  
Lateral Interaction ◽  
Tio2 Surface ◽  
High Toxicity ◽  
Removal Of Heavy Metals ◽  
Solution Parameters ◽  
Kinetics Of

The removal of heavy metals from wastewaters is a matter of paramount importance due to the fact that their high toxicity causes major environmental pollution problems. One of the most efficient, applicable and low cost methods for the removal of toxic metals from aqueous solutions is that of their adsorption on an inorganic adsorbent. In order to achieve high efficiency, it is important to understand the influence of the solution parameters on the extent of the adsorption, as well as the kinetics of the adsorption. In the present work, the adsorption of Cu(II) species onto TiO2 surface was studied. It was found that the adsorption is a rapid process and it is not affected by the value of ionic strength. In addition, it was found that by increasing the pH, the adsorbed amount of Cu2+ ions and the value of the adsorption constant increase, whereas the value of the lateral interaction energy decreases.

Particle Destabilization in Turbulent Pipe Flow

1989 ◽  
Vol 21 (6-7) ◽  
pp. 435-442 ◽  
Author(s):  
B. Döll
Keyword(s):  
Pipe Flow ◽  
Reaction Rate ◽  
Turbulent Pipe Flow ◽  
Cationic Polymers ◽  
Flow Conditions ◽  
Polyelectrolyte Adsorption ◽  
Charge Neutralization ◽  
Silica Suspensions ◽  
Kinetics Of ◽  
Turbulent Flow Conditions

Silica suspensions (pH = 6.8) and three different cationic polymers were used to study the kinetics of charge neutralization by polyelectrolyte adsorption. The experiments were performed in a continuous flow pipe reactor under steady state turbulent flow conditions. The charge neutralization was monitored by electrophoretic mobility (EPM) measurements of the suspended particles as a function of time after polyelectrolyte audition. The results show the dependency of the destabilization reaction rate on flow and polymer characteristics.

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