scholarly journals A kinetic study of irreversible enzyme inhibition by an inhibitor that is rendered unstable by enzymic catalysis. The inhibition of polyphenol oxidase by l-cysteine

1991 ◽  
Vol 277 (3) ◽  
pp. 869-874 ◽  
Author(s):  
E Valero ◽  
R Varón ◽  
F García-Carmona
Keyword(s):  
Kinetic Study ◽  
Polyphenol Oxidase ◽  
Dynamic Behaviour ◽  
Equation System ◽  
Enzymic Activity ◽  
Differential Equation System ◽  
Enzyme Substrate ◽  
Lag Period ◽  
Linear Differential ◽  
Kinetics Of

A kinetic study of the irreversible inhibition of an enzyme by an inhibitor that is depleted in the medium by its reaction with the product of enzymic analysis was made. The model is illustrated by the study of the inhibition of catecholase activity of polyphenol oxidase by L-cysteine. The inhibition is characterized by an initial lag period followed by a concomitant decrease in enzymic activity expressed when the steady state is reached, both kinetic parameters being modulated by enzyme, substrate and inhibitor concentrations. There is no analytical solution to the non-linear differential-equation system that describes the kinetics of the reaction, and so computer simulations of this dynamic behaviour are presented. The results obtained show that the system here studied presents kinetic co-operativity for a target enzyme that follows the simple Michaelis-Menten mechanism in its action on the substrate.

scholarly journals Theoretical Vibration Analysis Regarding Excitation due to Elliptical Shaft Journals in Sleeve Bearings of Electrical Motors

2012 ◽  
Vol 2012 ◽  
pp. 1-19 ◽  
Author(s):  
Ulrich Werner
Keyword(s):  
Differential Equation ◽  
Mathematical Description ◽  
Vibration Analysis ◽  
Equation System ◽  
Electrical Machines ◽  
Differential Equation System ◽  
Kinematic Constraints ◽  
Linear Differential ◽  
Electrical Motors ◽  
Rotor Mass

This paper shows a theoretical vibration analysis regarding excitation due to elliptical shaft journals in sleeve bearings of electrical motors, based on a simplified rotordynamic model. It is shown that elliptical shaft journals lead to kinematic constraints regarding the movement of the shaft journals on the oil film of the sleeve bearings and therefore to an excitation of the rotordynamic system. The solution of the linear differential equation system leads to the mathematical description of the movement of the rotor mass, the shaft journals, and the sleeve bearing housings. Additionally the relative movements between the shaft journals and the bearing housings are deduced, as well as the bearing housing vibration velocities. The presented simplified rotordynamic model can also be applied to rotating machines, other than electrical machines. In this case, only the electromagnetic spring valuecmhas to be put to zero.

scholarly journals Theory of Vibrations of Sugar Beet Leaf Harvester Front-Mounted on Universal Tractor

2017 ◽  
Vol 20 (4) ◽  
pp. 96-103 ◽  
Author(s):  
Volodymyr Bulgakov ◽  
Valerii Adamchuk ◽  
Ladislav Nozdrovický ◽  
Yevhen Ihnatiev
Keyword(s):  
Sugar Beet ◽  
System Development ◽  
Vertical Plane ◽  
Equation System ◽  
Design Parameters ◽  
Differential Equation System ◽  
Current Task ◽  
Leaf Cutting ◽  
Linear Differential ◽  
A Current

Abstract The harvest and transport of sugar beet leaves during harvesting can be considered a current task in the area of sugar beet growing system development. A rotary sugar beet leaf cutting mechanism is used for achieving the significant increase in the harvester forward speed during harvest. This leads to intensive vibrations of the topping mechanism in the longitudinal vertical plane causing the decrease of harvest quality. Therefore, it is necessary to analytically determine the effect of kinematic and design parameters of the sugar beet topping mechanism front-mounted on the tractor and to discover the value of the amplitude of oscillations in the longitudinal vertical plane of its sugar beet topping mechanism. We have constructed a mathematical model of the estimated motion of this machine by means of dynamics equations in Lagrange II-kind form. A system consisting of two non-linear differential equations was obtained by developing the equivalent scheme of selected generalized coordinates and by performing the necessary mathematical transformations. This system describes the vibrations of the sugar beet topping mechanism in the longitudinal vertical plane. The optimal design and kinematic parameters of the sugar beet topper mechanism front-mounted on the tractor were determined by means of our own software and numerical solution of the differential equation system, which allows the reduction of mentioned vibrations.

scholarly journals Partial purification and kinetics of oestriol 16α-glucuronyltransferase from the cytosol fraction of human liver

1970 ◽  
Vol 118 (4) ◽  
pp. 625-634 ◽  
Author(s):  
Govind S. Rao ◽  
Marie Luise Rao ◽  
Heinz Breuer
Keyword(s):  
Human Liver ◽  
Glucuronic Acid ◽  
Specific Radioactivity ◽  
Competitive Inhibitor ◽  
Enzymic Activity ◽  
Hydroxyl Group ◽  
Partial Purification ◽  
Cytosol Fraction ◽  
Enzyme Substrate ◽  
Kinetics Of

An enzyme that conjugates the 16α-hydroxyl group of oestriol with glucuronic acid was found in the cytosol fraction of human liver. The enzymic activity could not be sedimented when the cytosol fraction was centrifuged at 158000gav. for 120min. The oestriol 16α-glucuronyltransferase was purified 100-fold by 0–30% saturation of the cytosol fraction with ammonium sulphate followed by filtration of the precipitate through Sephadex G-200. The activity was eluted at the void volume. The product of the reaction, oestriol 16α-monoglucuronide, was identified by paper chromatography and by crystallization of radioactive product to constant specific radioactivity. The optimum temperature was 37°C, and the activation energy was calculated to be 11.1kcal/mol. The apparent Michaelis–Menten constants for oestriol and UDP-glucuronic acid were 13.3 and 100μm respectively. Cu2+, Zn2+ and Hg2+ inhibited, whereas Mg2+, Mn2+ and Fe2+ stimulated the enzyme. Substrate-specificity studies indicated that the amount of oestradiol-17β, oestradiol-17α and oestrone conjugated was not more than about 5% of that found for oestriol. Oestriol 16α-monoglucuronide, a product of the reaction, did not inhibit the 16α-oestriol glucuronyltransferase; in contrast, UDP, another product of the reaction, inhibited the enzyme competitively with respect to UDP-glucuronic acid as the substrate, and non-competitively with respect to oestriol as the substrate. ATP and UDP-N-acetylglucosamine did not affect the oestriol 16α-glucuronyltransferase. 17-Epioestriol acted as a competitive inhibitor and 16-epioestriol as a non-competitive inhibitor of the glucuronidation of oestriol. 5α-Pregnane-3α,20α-diol also inhibited the enzyme non-competitively. It is most likely that the oestriol 16α-glucuronyltransferase described here is bound to the membranes of the endoplasmic reticulum.

Sensitivity of Hurwitz stability of linear differential equation systems with constant coefficients

2017 ◽  
Vol 14 (06) ◽  
pp. 1750084
Author(s):  
Ahmet Duman ◽  
Kemal Aydin
Keyword(s):  
Differential Equation ◽  
Differential Equations ◽  
Linear Differential Equation ◽  
Equation System ◽  
Linear Differential Equations ◽  
Differential Equation System ◽  
Hurwitz Stability ◽  
Constant Coefficients ◽  
Linear Differential ◽  
Stable Linear

For Hurwitz stable linear differential equation system with constant coefficients, we have proved continuity theorems which show how much change is permissible without disturbing the Hurwitz stability and the [Formula: see text]-Hurwitz stability. The results have been applied to the scalar–linear differential equations with order [Formula: see text] and some examples illustrating the efficiency of the theorems have been given.

scholarly journals Transient Dynamics in the Random Growth and Reset Model

Entropy ◽  
2021 ◽  
Vol 23 (3) ◽  
pp. 306
Author(s):  
Tamás S. Biró ◽  
Lehel Csillag ◽  
Zoltán Néda
Keyword(s):  
Differential Equation ◽  
Mean Field ◽  
Equation System ◽  
Transient Dynamics ◽  
Type Model ◽  
Discrete Version ◽  
Differential Equation System ◽  
Practical Applications ◽  
Random Growth ◽  
Recursive Integration

A mean-field type model with random growth and reset terms is considered. The stationary distributions resulting from the corresponding master equation are relatively easy to obtain; however, for practical applications one also needs to know the convergence to stationarity. The present work contributes to this direction, studying the transient dynamics in the discrete version of the model by two different approaches. The first method is based on mathematical induction by the recursive integration of the coupled differential equations for the discrete states. The second method transforms the coupled ordinary differential equation system into a partial differential equation for the generating function. We derive analytical results for some important, practically interesting cases and discuss the obtained results for the transient dynamics.

A Kinetic Study of the Thermal Isomerization of and Related Complexes

1975 ◽  
Vol 53 (12) ◽  
pp. 1735-1738 ◽  
Author(s):  
William R. Cullen ◽  
Frank L. Hou
Keyword(s):  
Kinetic Study ◽  
Thermal Isomerization ◽  
Isomerization Reaction ◽  
Kinetics Of

The kinetics of the unimolecular isomerization reaction[Formula: see text]have been studied. The ΔH≠ values in kcal mol−1 are 36.8 ± 2.0 (M = M′ = Mn ), 46.8 ± 0.5 (M = M′ = Re ), 39.2 ± 2.8 (M = Mn, M′ = Re ). The mechanism of the rearrangement is discussed.

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