On the kinetics of the Langmuir-type heterogeneous reactions

2011 ◽  
Vol 16 (4) ◽  
pp. 467-476 ◽  
Author(s):  
Vladas Skakauskas ◽  
Pranas Katauskis
Keyword(s):  
Steady State ◽  
Surface Coverage ◽  
Surface Reactions ◽  
Heterogeneous Reactions ◽  
The Other ◽  
Two Dimensional ◽  
Finite Difference Technique ◽  
Planar Surfaces ◽  
Adsorption Desorption ◽  
Kinetics Of

In this paper we investigate three two-dimensional in space mathematical models of the kinetics of unimolecular heterogeneous reactions proceeding onto planar surfaces. All models include the diffusion of the reactant from a bounded vessel towards an adsorbent, adsorption of the molecules of the reactant, their desorption, conversion (reaction) of the adsorbate into a product, instantaneous product desorption, and the diffusion of the product from the adsorbent into the same vessel. One of these models is based on the Langmuir-type kinetics of the surface reactions, the other one is based on the local steady-state value of the surface coverage, and the last one, in addition to the first model, involves the diffusion of the adsorbate along the adsorbent. Diffusivity of all species is assumed to be constant. Models were solved numerically by using the finite difference technique. By changing input parameters the effects of the rate constants of the reactant adsorption, desorption, and reaction and the influence of the surface diffusion of the adsorbate and approximation of the surface coverage by its steady-state value on the kinetics of surface reactions were studied numerically.

Determining the Morphology and the Interaction Between Terminally-Anchored Polymer Layers

1996 ◽  
Vol 461 ◽  
Author(s):  
A. C. Balazs ◽  
C. Singh
Keyword(s):  
Field Theory ◽  
Colloidal Particles ◽  
The Other ◽  
Two Dimensional ◽  
Planar Surfaces ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Energy Of Interaction ◽  
Self Consistent Field Theory

ABSTRACTUsing a two dimensional self-consistent field theory, we investigate the interactions between two planar surfaces that are coated with terminally-anchored homopolymers. One surface is coated with A chains and the other is covered with B homopolymers. The chains are grafted at low densities and the B polymers are chosen to be solvophobic, while the A chains are relatively solvophilic. We determine the morphology of the layers and the energy of interaction asthe surfaces are compressed. Our results provide guidelines for controlling the interaction between polymer-coated colloidal particles.

Chemical kinetics at solid-solid interfaces

2000 ◽  
Vol 72 (11) ◽  
pp. 2137-2147 ◽  
Author(s):  
Hermann Schmalzried
Keyword(s):  
Solid State ◽  
Moving Boundaries ◽  
Heterogeneous Reactions ◽  
Solid State Reactions ◽  
Nonlinear Phenomena ◽  
Two Dimensional ◽  
Interface Morphology ◽  
Interface Kinetics ◽  
Reaction Media ◽  
Kinetics Of

The kinetics of solid-solid interfaces controls in part the course of heterogeneous reactions in the solid state, in particular in miniaturized systems. In this paper, the essential situations of interface kinetics in solids are defined, and the basic formal considerations are summarized. In addition to the role interfaces play as resistances for transport across them, they offer high diffusivity paths laterally and thus represent two-dimensional reaction media. Experimental examples will illustrate the kinetic phenomena at static and moving boundaries, including problems such as exchange fluxes, boundary-controlled solid-state reactions, interface morphology, nonlinear phenomena connected with interfaces, and reactions in and at boundaries, among others.

Calcium removal kinetics of the sarcoplasmic reticulum ATPase in skeletal muscle

1997 ◽  
Vol 272 (4) ◽  
pp. C1087-C1098 ◽  
Author(s):  
E. E. Burmeister Getz ◽  
S. L. Lehman
Keyword(s):  
Skeletal Muscle ◽  
Steady State ◽  
Sarcoplasmic Reticulum ◽  
Initial Rate ◽  
Troponin C ◽  
The Other ◽  
Physiological Conditions ◽  
Initial Binding ◽  
Kinetics Of ◽  
Transient And Steady State

The models of the sarcoplasmic reticulum (SR) Ca pump used to simulate Ca kinetics in muscle fibers are simple but inconsistent with data on Ca binding or steady-state uptake. We develop a model of the SR pump that is consistent with data on transient and steady-state Ca removal and has rate constants identified under near-physiological conditions. We also develop models of the other main Ca-binding proteins in skeletal muscle: troponin C and parvalbumin. These models are used to simulate Ca transients in cut fibers during and after depolarizing pulses. Simulations using the full SR pump model are contrasted with simulations using a Michaelis-Menten (MM) approximation to SR pump kinetics. The MM pump underestimates the amount of Ca released during depolarization, underestimates the initial rate of Ca binding by the pump, and overestimates the later rate of Ca pumping. These errors are due to fast initial binding by the SR pump, which is neglected in the MM approximation.

scholarly journals Spread of synaptic potentials through electrical synapses in Retzius neurones of the leech

2001 ◽  
Vol 204 (19) ◽  
pp. 3241-3250 ◽  
Author(s):  
Francisco F. De-Miguel ◽  
Mariana Vargas-Caballero ◽  
Elizabeth García-Pérez
Keyword(s):  
Steady State ◽  
Current Injection ◽  
The Other ◽  
Electrical Synapse ◽  
Coupling Ratio ◽  
Electrical Synapses ◽  
Postsynaptic Potentials ◽  
Synaptic Potentials ◽  
Kinetics Of ◽  
Bathing Fluid

SUMMARYWe studied the spread of excitatory postsynaptic potentials (EPSPs) through electrical synapses in Retzius neurones of the leech Haementeria officinalis. The pair of Retzius neurones in each ganglion is coupled by a non-rectifying electrical synapse. Both neurones displayed synchronous EPSPs of varying amplitudes and rise times. The kinetics of synchronous EPSPs was similar in 79 % of the EPSP pairs. In the remaining 21 %, one EPSP was smaller and slower than the other, suggesting its passive spread from the other neurone. The proportion of these events increased to 75 % in the presence of Mg2+ in the bathing fluid. This spread of EPSPs from one neurone to another was tested by producing artificial EPSPs by current injection into the soma of one Retzius neurone. The artificial EPSPs were smaller and arrived more slowly at the soma of the coupled neurone. The coupling ratios for the EPSPs were proportional to the coupling ratio for long steady-state pulses in different neuronal pairs. Our results showed that EPSPs spread from one Retzius neurone to the other and support the idea that EPSP spread between electrically coupled neurones may contribute to the integration processes of neurones.

Computational Modelling of a Sensor Based on an Array of Enzyme Microreactors

2004 ◽  
Vol 9 (3) ◽  
pp. 203-218 ◽  
Author(s):  
R. Baronas ◽  
F. Ivanauskas ◽  
J. Kulys ◽  
M. Sapagovas
Keyword(s):  
Digital Simulation ◽  
Enzymatic Reaction ◽  
Computational Modelling ◽  
Enzyme Reaction ◽  
Diffusion Region ◽  
Two Dimensional ◽  
Analyte Concentration ◽  
Finite Difference Technique ◽  
Kinetics Of ◽  
Biosensor Response

This paper presents a two-dimensional-in-space mathematical model of a sensor system based an array of enzyme microreactors immobilised on a single electrode. The system acts under amperometric conditions. The model is based on the diffusion equations containing a non-linear term related to the Michaelis-Menten kinetics of the enzymatic reaction. The model involves three regions: an array of enzyme microreactors (cells) where enzyme reaction as well as mass transport by diffusion takes place, a diffusion limiting region where only the diffusion takes place, and a convective region, where the analyte concentration is maintained constant. Using computer simulation the influence of the geometry of the enzyme cells and the diffusion region on the biosensor response was investigated. The digital simulation was carried out using the finite difference technique.

Three-Dimensional Reconstruction of Two Forms of the Chaperonin GRO EL

1990 ◽  
Vol 48 (1) ◽  
pp. 258-259
Author(s):  
J.L. Carrascosa ◽  
G. Abella ◽  
S. Marco ◽  
M. Muyal ◽  
J.M. Carazo
Keyword(s):  
Three Dimensional ◽  
The Other ◽  
Two Dimensional ◽  
Series Method ◽  
Three Dimensional Reconstruction ◽  
Structural Components ◽  
E Coli ◽  
Dimensional Reconstruction ◽  
Morphogenetic Factors ◽  
Tilt Series

Chaperonins are a class of proteins characterized by their role as morphogenetic factors. They trantsiently interact with the structural components of certain biological aggregates (viruses, enzymes etc), promoting their correct folding, assembly and, eventually transport. The groEL factor from E. coli is a conspicuous member of the chaperonins, as it promotes the assembly and morphogenesis of bacterial oligomers and/viral structures.We have studied groEL-like factors from two different bacteria:E. coli and B.subtilis. These factors share common morphological features , showing two different views: one is 6-fold, while the other shows 7 morphological units. There is also a correlation between the presence of a dominant 6-fold view and the fact of both bacteria been grown at low temperature (32°C), while the 7-fold is the main view at higher temperatures (42°C). As the two-dimensional projections of groEL were difficult to interprete, we studied their three-dimensional reconstruction by the random conical tilt series method from negatively stained particles.

Sign in / Sign up

Export Citation Format

Share Document