scholarly journals An allosteric model for ribonuclease.

1975 ◽  
Vol 147 (3) ◽  
pp. 425-433 ◽  
Author(s):  
E J Walker ◽  
G B Ralston ◽  
I G Darvey
Keyword(s):  
Experimental Data ◽  
Velocity Versus ◽  
Physical Evidence ◽  
Substrate Analogues ◽  
Dependent Change ◽  
Calculated Curve ◽  
Conventional Models ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Allosteric Model

Data from two assay systems show that the kinetics of the hydrolysis of cytidine 2′:3′-cyclic monophosphate by bovine pancreatic RNAase (ribonuclease) is not consistent with conventional models. An allosteric model involving a substrate-dependent change in the equilibrium between two enzyme conformations is proposed. Such a model gives rise to a calculated curve of velocity versus substrate concentration which fits the experimental data. The model is also consistent with the results of an examination of the tryptic digestion of RNAase. Substrate analogues are able to protect RNAase against hydrolysis by trypsin and the percentage of RNAase activity which remains after digestion increases sigmoidally as the analogue concentration is increased. The model also explains the pattern seen in the Km values quoted in the literature and is consistent with strong physical evidence for a ligand-induced conformational change for RNAase reported in the literature.

Untersuchung der alkalischen Hydrolyse des Benzoesäurebenzylesters in Wasser-Äthanol 1 : 1 / Study of the Basic Hydrolysis of Benzyl Benzoate in Water-Ethyl Alcohol 1:1

1974 ◽  
Vol 29 (11) ◽  
pp. 1697-1698 ◽  
Author(s):  
F. Mansilla ◽  
P. Martinez ◽  
J. Sancho
Keyword(s):  
Experimental Data ◽  
Reaction Mechanism ◽  
Order Rate Constant ◽  
Benzyl Benzoate ◽  
Conductometric Method ◽  
Alcohol Medium ◽  
Basic Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Water Alcohol

By using a conductometric method, the kinetics of the basic hydrolysis of benzyl benzoate in water-alcohol medium has been investigated. The second order rate constant follows the equation K = A exp {-E/RT} with A = 1.35·1010 l mol-1 min-1 and E = 14.5 kcal mol-1. A reaction mechanism is postulated, which is consistent with the experimental data.

scholarly journals Further evidence for an allosteric model for ribonuclease

1976 ◽  
Vol 153 (2) ◽  
pp. 329-337 ◽  
Author(s):  
E J Walker ◽  
G B Ralston ◽  
I G Darvey
Keyword(s):  
Conformational Change ◽  
Equilibrium Dialysis ◽  
Kinetic Studies ◽  
Experimental Systems ◽  
Substrate Analogues ◽  
Multiple Binding ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Cyclic Cmp ◽  
Allosteric Model

Evidence is presented from three experimental systems to support the allosteric model of Walker et al. (1975) (Biochem. J. 147, 425-433) which explains the substrate-concentration-dependent transition observed in the RNAase (ribonuclease)-catalysed hydrolysis of 2‘:3’-cyclic CMP (cytidine 2‘:3’-cyclic monophosphate). 1. Kinetic studies of the initial rate of hydrolysis of 2‘:3’-cyclic CMP show that the midpoint of the transition shifts to lower concentrations of 2‘:3’-cyclic CMP in the presence of the substrate analogues 3′-CMP, 5′-CMP, 3′-AMP, 3′-UMP and Pi; 2′-CMP and 2′-UMP do not cause such a shift. 2. Trypsin-digestion studies show that a conformational change in RNAase to a form less susceptible to tryptic inactivation is induced in the presence of the substrate analogues 3′-CMP, 5′-CMP, 3′-AMP, and 3′-UMP. 2′-CMP, 2′-AMP and 2′-UMP do not induce this conformational change. 3. Equilibrium-dialysis experiments demonstrate the multiple binding of molecules of 3′-CMP, 3′-AMP and 5′-AMP to a molecule of RNAase. 2′-CMP binds the ratio 1:1 over the analogue concentration range studied.

Calculation of isokinetic temperature of non-catalyzed hydrolysis of substituted 3-(N-methylcarbamoyl)-1,3-diphenyltriazenes

1981 ◽  
Vol 46 (4) ◽  
pp. 898-905 ◽  
Author(s):  
Oldřich Pytela ◽  
Miroslav Večeřa ◽  
Pavel Vetešník
Keyword(s):  
Experimental Data ◽  
Isokinetic Temperature ◽  
Reaction Series ◽  
Significance Level ◽  
Common Intersection ◽  
Reaction Constant ◽  
Straight Lines ◽  
The Given ◽  
Kinetics Of ◽  
Hydrolysis Of

Temperature dependence of kinetics of non-catalyzed hydrolysis of substituted 3-(N-methylcarbamoyl)-1,3-diphenyltriazines has been measured. An optimized calculation method has been suggested for calculation of the isokinetic temperature and the experimental data have been evaluated. In all the cases it has been found that the hypothesis of common intersection of the straight lines log k vs1/T is rejected at the significance level α = 0.05, but, within approximate validity of the isokinetic hypothesis the isokinetic relation can be considered to be fulfilled in the given reaction series. The change of the reaction constant ρ connected with the change of the reaction mechanism shows a statistically significant correspondence with the change of the isokinetic temperature.

Kinetics of Catalytic Dehydration of 1-Pentanol

1993 ◽  
Vol 58 (8) ◽  
pp. 1874-1884 ◽  
Author(s):  
Iveta Vašutová ◽  
Milan Králik ◽  
Milan Hronec
Keyword(s):  
Experimental Data ◽  
Kinetic Data ◽  
Potassium Hydroxide ◽  
Molar Fraction ◽  
Space Velocity ◽  
Continuous Reactor ◽  
Alumina Catalyst ◽  
Direct Formation ◽  
Kinetics Of ◽  
Hydrolysis Of

Kinetic data of 1-pentanol dehydration on γ-alumina catalyst modified by potassium hydroxide were obtained using a continuous reactor with an internal recirculation. The conversion of 1-pentanol on this catalyst in the temperature range 300 - 390 °C and space velocity 1 - 8 kg (h kg)-1 (molar fraction of water in the feed was in the range 0 - 0.56) was 50 - 98% and the selectivity with respect to 1-pentene was 50 - 84%. The following six reactions have been taken into account to describe the catalytic dehydration of 1-pantanol: direct formation of 1-pentene from 1-pentanol, formation of bis(1-pentyl) ether from 1-pentanol, disproportionation of the ether to 1-pentanol and 1-pentene, formation of 1-pentene from the ether, isomerization of 1-pentene to 2-pentene and hydrolysis of the ether to 1-pentanol. Treatment of experimental data by Langmuir-Hinshelwood models showed that the model involving adsorption of 1-pentanol accompanied by dissociation is the most suitable one.

scholarly journals STUDY OF THE ADSORPTION OF METHYLENE BLUE DYE IN CHITOSAN MICROSPHERES

2015 ◽  
Vol 12 (24) ◽  
pp. 28-34
Author(s):  
, Anna Karla dos Santos; ,, , PEREIRA ◽  
Gessiel Newton SCHEIDT ◽  
Lucas Samuel Soares SANTOS
Keyword(s):  
Experimental Data ◽  
Chemical Structure ◽  
Blue Dye ◽  
Maximum Adsorption Capacity ◽  
Methylene Blue Dye ◽  
Adsorption Model ◽  
Adsorption Sites ◽  
Pseudo Second Order ◽  
Kinetics Of ◽  
Hydrolysis Of

Chitosan is a polymer that can be used as adsorbent material. In this work, chitosan was synthesized via alkaline hydrolysis of chitin. The chemical structure was characterized by IR spectroscopy and the degree of deacetylation (% DG) of the acetamido groups present in the polymer matrix by neutralization titration. The most suitable adsorption model for analysis of experimental data was Langmuir. The maximum adsorption capacity of the microspheres (Ns) of chitosan was 3.36 x 10-6 mol g-1 adsorbent. The rate of adsorption is governed by the kinetics of the pseudo-second order, where the saturation of adsorption sites occurred after two hours of contact between the adsorbent and the adsorbate. By analyzing data across the isotherm model Dubinin-Radushkevich (DR) it was found that this process adsorption is physical in nature.

Hydrolysis Kinetics of Straw Biomass Catalyzed by Diluted Sulphuric Acid in the Present of Fe2+

2012 ◽  
Vol 550-553 ◽  
pp. 484-487 ◽  
Author(s):  
Chong Wen Jiang ◽  
Can Chen Bai ◽  
Hao Xiao
Keyword(s):  
Experimental Data ◽  
Sulfuric Acid ◽  
Kinetic Model ◽  
Acid Catalyst ◽  
Fermentable Sugars ◽  
Hydrolysis Kinetics ◽  
First Order ◽  
Sulfuric Acid Catalyst ◽  
Kinetics Of ◽  
Hydrolysis Of

This study focuses on kinetics of straw hydrolysis using sulfuric acid catalyst to produce fermentable sugars. The result shows the degradation of sugars is encountered during the hydrolysis of straw biomass. A consecutive first-order reactions kinetic model is proposed and the kinetic model well agrees with the experimental data. It turns out that rate of sugar formation and degradation is small at lower experimental temperature. The reactions rates constant k1 including the formation of sugar begins to increase rapidly when the Fe2+concentration increases from 0.125 to 0.500molL-1. However, the rate constant k2 relevant with the degradation of sugar varies unsensibly below 0.375molL-1 Fe2+and it is accelerated as the Fe2+concentration increases to 0.500molL-1. Thus the optimum yield is obtained at 0.375molL-1 Fe2+concentration.

Alkaline hydrolysis of methyl hydrogen malonate in water-organic solvents

1986 ◽  
Vol 51 (6) ◽  
pp. 1187-1194 ◽  
Author(s):  
Oľga Grančičová ◽  
Vladislav Holba ◽  
Ľudmila Beluská
Keyword(s):  
Experimental Data ◽  
Ethylene Glycol ◽  
Alkaline Hydrolysis ◽  
Transfer Functions ◽  
Butyl Alcohol ◽  
Gibbs Energies ◽  
Tert Butyl Alcohol ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Activated Complex

Kinetics of alkaline hydrolysis of methyl hydrogen malonate in water-methanol, water-dioxane, water-tert-butyl alcohol and water-ethylene glycol mixtures was examined. The valuse of the transfer functions of the activated complex δmμ≠ from water to the first two mixed media were calculated from the measured solubilities of tetrabutylammonium hydrogen malonate, the activation Gibbs energies and the known values of transfer functions for tetrabutylammonium and hydroxide ions. Some conclusions concerning the effect of a nonaqueous component of the solvent on solvation of the reactants and the activated complex have been drawn from the experimental data obtained.

scholarly journals Kinetics of Alkaline Hydrolysis of Synthetic Organic Esters

2021 ◽  
Author(s):  
Do Young Maeng ◽  
V. Faye McNeill
Keyword(s):  
Experimental Data ◽  
Alkaline Hydrolysis ◽  
Indoor Environment ◽  
Organic Esters ◽  
Kinetics Of ◽  
Hydrolysis Of

Manuscript with supporting information describing novel experimental data on the alkaline hydrolysis of synthetic esters, relevant to chemistry in the indoor environment

scholarly journals Kinetics of Alkaline Hydrolysis of Synthetic Organic Esters

2021 ◽  
Author(s):  
Do Young Maeng ◽  
V. Faye McNeill
Keyword(s):  
Experimental Data ◽  
Alkaline Hydrolysis ◽  
Indoor Environment ◽  
Organic Esters ◽  
Kinetics Of ◽  
Hydrolysis Of

Manuscript with supporting information describing novel experimental data on the alkaline hydrolysis of synthetic esters, relevant to chemistry in the indoor environment

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