scholarly journals Rate studies of polysaccharide biosynthesis from guanosine diphosphate α-d-glucose and guanosine diphosphate α-d-mannose

1971 ◽  
Vol 121 (1) ◽  
pp. 151-157 ◽  
Author(s):  
C. L. Villemez
Keyword(s):  
Reaction Rate ◽  
Initial Rate ◽  
Competitive Inhibitor ◽  
Enzyme Preparations ◽  
Polysaccharide Biosynthesis ◽  
Guanosine Diphosphate ◽  
Straight Line ◽  
Kinetics Of ◽  
Total Reaction Time ◽  
Stimulation Of

With enzyme preparations from Phaseolus aureus seedlings, the initial rate of 14C-labelled polysaccharide formation from GDP-α-d-[14C]glucose is not increased by additions of GDP-α-d-mannose. However, final incorporation is increased by addition of GDP-α-d-mannose, since the total reaction-time is extended. In contrast, the initial rate of 14C-labelled polysaccharide formation from GDP-α-d-[14C]mannose is increased by all concentrations of GDP-α-d-glucose that are less than that of the GDP-α-d-[14C]mannose. Maximum stimulation of the initial rate occurs at a GDP-α-d-[14C]mannose/GDP-α-d-glucose concentration ratio of about 4:1. However, eventual incorporation from GDP-α-d-[14C]mannose is decreased by the addition of GDP-α-d-glucose, since the reaction rate falls off sharply after about 2min. Reciprocal plots of 14C-labelled polysaccharide formation from GDP-α-d-[14C]mannose result in biphasic graphs. The two straight-line portions of the plot are joined by a curved line in the concentration range between 2–3 and 50μm. Extrapolated Km values for the two linear components are 0.4–1.0 and 700–1500μm. The effect of GDP-α-d-glucose on the kinetics of 14C-labelled polysaccharide formation from GDP-α-d-[14C]mannose is complex, and depends on relative concentrations of the two sugar nucleotides. 14C-labelled polysaccharide formation from GDP-α-d-[14C]glucose also results in biphasic reciprocal plots. One component appears to have Km about 2–3μm, the other about 200–400μm. In this reaction, GDP-α-d-mannose appears to be a competitive inhibitor with Ki 20–30μm. With particulate preparations of P. aureus, GDP-α-d-[14C]glucose appears to be a precursor for the synthesis of one polysaccharide, a glucomannan, the mannose moieties of which are derived from an intermediate existing in the particulate preparation. From the rate results, GDP-α-d-[14C]mannose appears to be a precursor for at least two polysaccharides, one of which is a glucomannan.

scholarly journals THE KINETICS OF CELLULAR COMMITMENT DURING STIMULATION OF LYMPHOCYTES BY LECTINS

1974 ◽  
Vol 62 (2) ◽  
pp. 366-377 ◽  
Author(s):  
Gary R. Gunther ◽  
John L. Wang ◽  
Gerald M. Edelman
Keyword(s):  
Cellular Response ◽  
Thymidine Incorporation ◽  
Competitive Inhibitor ◽  
Spleen Cells ◽  
Con A ◽  
Induction Periods ◽  
Blast Cells ◽  
Staining Techniques ◽  
Kinetics Of ◽  
Stimulation Of

The kinetics of cellular commitment in the stimulation of lymphocytes by concanavalin A (Con A) has been analyzed by measurement of DNA synthesis, autoradiography, and histologic staining techniques. If the competitive inhibitor α-methyl-D-mannoside (αMM) is introduced into cultures of mouse spleen cells at various times after the addition of Con A, there is a gradual decrease in its capacity to inhibit the lectin-stimulated incorporation of [3H]thymidine. Addition of the saccharide 20 h after exposure of the cells to Con A had no effect on the level of the cellular response to the lectin. With increasing periods of contact with Con A, the percentage of blast cells and the percentage of [3H]thymidine-labeled blast cells increased in parallel with the total radioactive thymidine incorporated while the average number of autoradiographic grains per labeled blast cell remained relatively constant. These observations suggest that the rising level of [3H]thymidine incorporation results from an increase in the number of cells that respond to lectin stimulation and become refractory to inhibition with αMM. Once such cells become committed, they synthesize DNA at a rate independent of the length of exposure to the lectin. The combined results indicate that mouse splenic lymphocytes are heterogeneous in their capacities to respond to Con A and that different cells require different induction periods to be stimulated.

scholarly journals A Competitive Inhibitor of Tyrosinase

1951 ◽  
Vol 4 (4) ◽  
pp. 554 ◽  
Author(s):  
C Warner
Keyword(s):  
Enzyme Inhibitor ◽  
Dissociation Constants ◽  
Competitive Inhibitor ◽  
Enzyme Preparations ◽  
Enzyme Substrate ◽  
Kinetics Of

The kinetics of the activation of catechol by tyrosinase prepared from the potato and the mushroom, and of its inhibition by sodium m-hydroxybenzoate, have been studied. The enzyme-substrate dissociation constants differed markedly between the two enzyme sources (K. potato = 5.OmM, Kg mushroom = O.28mM), as did also the enzyme-inhibitor dissociation constants (K; potato = 2.5mM, Ki mushroom = O.BmM). For both enzyme preparations sodium m-hydroxybenzoate met the requirements of a competitive inhibitor.

Rate of reaction of dithionite ion with oxygen in aqueous solution

1964 ◽  
Vol 19 (3) ◽  
pp. 522-525 ◽  
Author(s):  
J. A. Morello ◽  
Margot R. Craw ◽  
H. P. Constantine ◽  
R. E. Forster
Keyword(s):  
Aqueous Solution ◽  
Reaction Rate ◽  
Initial Rate ◽  
Sodium Dithionite ◽  
Zero Order ◽  
Flowing Liquid ◽  
First Order ◽  
Rate Of Reaction ◽  
Dithionite Ion ◽  
Kinetics Of

The rate of removal of oxygen from aqueous solution by sodium dithionite in 0.1 m sodium hydroxide was studied in a rapid-reaction apparatus using a membrane-covered polarographic cell to determine Po2 in the flowing liquid. The measurements were made at 37 C, so that the data would be applicable in studies of the kinetics of oxyhemoglobin in blood. The initial concentrations in the mixed reacting solution were between 8 x 10-5 m and 47.5 x 10-5 m for dithionite, and either 10 x 10-5 m or 47.8 x 10-5 m for O2. The reaction over the first 40 msec was found to be first order with respect to dithionite and zero order with respect to molecular oxygen. The initial rate constant was 42.5 ± sd 3.6 sec-1. oxygen reduction by dithionite; hemoglobin; deoxygenation rate; dithionite-oxygen reaction rate Submitted on June 17, 1963

Kinetics of the Reaction for Generation of Chlorine Dioxide from Sodium Chlorate and Hydrochloric Acid

2013 ◽  
Vol 634-638 ◽  
pp. 546-550
Author(s):  
Xin Jie Li ◽  
Dan Dan Jiang ◽  
Yue Jun Zhang
Keyword(s):  
Hydrochloric Acid ◽  
Chlorine Dioxide ◽  
Reaction Rate ◽  
Initial Rate ◽  
Reaction System ◽  
Sodium Chlorate ◽  
Second Order ◽  
First Order ◽  
Mixed Order ◽  
Kinetics Of

Based on the mechanism of ClO3-/Cl-reaction system, the kinetics for reaction of sodium chlorate and hydrochloric acid to generate ClO2was studied. The rate equation of this reaction system was deduced and simplified as a formula with mixed-order (combination of first-order and second-order) towards ClO3-. This rate formula indicates that the initial rate of the reaction is the first-order with respect to ClO3-, and the reaction rate is the second-order with respect to ClO3-when [ClO3-] becomes close to zero. The rate constants of the first-order were determined as 0.0168s-1(30°C), 0.0221s-1(40°C), and 0.0279s-1(50°C), respectively, and that of the second-order were obtained for 0.0019L·mol-1·s-1(30°C), 0.0028L·mol-1·s-1(40°C), and 0.0060L·mol-1·s-1(50°C), respectively. The results of statistic test prove that the rate formula obtained in this work is credible.

Kinetic Aspects of the Interaction of Blood Clotting Enzymes

1968 ◽  
Vol 19 (03/04) ◽  
pp. 364-367 ◽  
Author(s):  
H. C Hemker ◽  
P. W Hemker
Keyword(s):  
Enzyme Kinetics ◽  
Blood Clotting ◽  
Competitive Inhibition ◽  
Competitive Inhibitor ◽  
Kinetics Of

SummaryThe enzyme kinetics of competitive inhibition under conditions prevailing in clotting tests are developed and a method is given to measure relative amounts of a competitive inhibitor by means of the t — D plot.

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>

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.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

Kinetics of carbon monoxide methanation on a Ni/SiO2 catalyst

1990 ◽  
Vol 55 (7) ◽  
pp. 1678-1685
Author(s):  
Vladimír Stuchlý ◽  
Karel Klusáček
Keyword(s):  
Carbon Monoxide ◽  
Reaction Rate ◽  
Catalyst Activity ◽  
Adsorbed Hydrogen ◽  
Reaction Products ◽  
Co Methanation ◽  
Molar Ratios ◽  
Rate Determining Step ◽  
Higher Temperature ◽  
Kinetics Of

Kinetics of CO methanation on a commercial Ni/SiO2 catalyst was evaluated at atmospheric pressure, between 528 and 550 K and for hydrogen to carbon monoxide molar ratios ranging from 3 : 1 to 200 : 1. The effect of reaction products on the reaction rate was also examined. Below 550 K, only methane was selectively formed. Above this temperature, the formation of carbon dioxide was also observed. The experimental data could be described by two modified Langmuir-Hinshelwood kinetic models, based on hydrogenation of surface CO by molecularly or by dissociatively adsorbed hydrogen in the rate-determining step. Water reversibly lowered catalyst activity and its effect was more pronounced at higher temperature.

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