Accurate Determination of Rate Constants of Very Slow, Tight-Binding Competitive Inhibitors by Numerical Solution of Differential Equations, Independently of Precise Knowledge of the Enzyme Concentration

2001 ◽  
Vol 295 (2) ◽  
pp. 186-193 ◽  
Author(s):  
Igor W. Plesner ◽  
Anne Bülow ◽  
Mikael Bols
Keyword(s):  
Differential Equations ◽  
Numerical Solution ◽  
Rate Constants ◽  
Accurate Determination ◽  
Tight Binding ◽  
Enzyme Concentration ◽  
Precise Knowledge ◽  
Competitive Inhibitors

scholarly journals Binding of NAD+ by cholera toxin

1987 ◽  
Vol 244 (1) ◽  
pp. 225-230 ◽  
Author(s):  
T S Galloway ◽  
S van Heyningen
Keyword(s):  
Binding Site ◽  
Dissociation Constant ◽  
Cholera Toxin ◽  
Equilibrium Dialysis ◽  
Accurate Determination ◽  
Polyacrylamide Gel ◽  
Nad Glycohydrolase ◽  
Competitive Inhibitors ◽  
Dissociation Constant Kd

1. The Km for NAD+ of cholera toxin working as an NAD+ glycohydrolase is 4 mM, and this is increased to about 50 mM in the presence of low-Mr ADP-ribose acceptors. Only molecules having both the adenine and nicotinamide moieties of NAD+ with minor alterations in the nicotinamide ring can be competitive inhibitors of this reaction. 2. This high Km for NAD+ is also reflected in the dissociation constant, Kd, which was determined by a variety of methods. 3. Results from equilibrium dialysis were subject to high error, but showed one binding site and a Kd of about 3 mM. 4. The A1 peptide of the toxin is digested by trypsin, and this digestion is completely prevented by concentrations of NAD+ above 50 mM. Measurement (by densitometric scanning of polyacrylamide-gel electrophoretograms) of the rate of tryptic digestion at different concentrations of NAD+ allowed a more accurate determination of Kd = 4.0 +/- 0.4 mM. Some analogues of NAD+ that are competitive inhibitors of the glycohydrolase reaction also prevented digestion.

Extremely fast retrieval of volcanic SO2 layer heights from UV satellite data using inverse learning machines

2021 ◽  
Author(s):  
Pascal Hedelt ◽  
MariLiza Koukouli ◽  
Konstantinos Michaelidis ◽  
Taylor Isabelle ◽  
Dimitris Balis ◽  
...  
Keyword(s):  
Real Time ◽  
Accurate Determination ◽  
Principal Component ◽  
Volcanic Eruptions ◽  
Neural Network Approach ◽  
Layer Height ◽  
Precise Knowledge ◽  
Innovation Project ◽  
Learning Machine

<p>Precise knowledge of the location and height of the volcanic sulfur dioxide (SO<sub>2</sub>) plume is essential for accurate determination of SO<sub>2</sub> emitted by volcanic eruptions, however so far not available in operational near-real time UV satellite retrievals. The FP_ILM algorithm (Full-Physics Inverse Learning Machine) enables for the first time to extract the SO<sub>2</sub> layer height information in a matter of seconds for current UV satellites and is thus applicable in NRT environments.</p><p>The FP_ILM combines a principal component analysis (PCA) and a neural network approach (NN) to extract the information about the volcanic SO<sub>2</sub> layer height from high-resolution UV satellite backscatter measurements. So far, UV based SO<sub>2 </sub>layer height retrieval algorithms were very time-consuming and therefore not suitable for near-real-time applications like aviation control, although the SO<sub>2</sub> LH is essential for accurate determination of SO<sub>2</sub> emitted by volcanic eruptions.</p><p>In this presentation, we will present the latest FP_ILM algorithm improvements and show results of recent volcanic eruptions.</p><p>The SO<sub>2</sub> layer height product for Sentinel-5p/TROPOMI is developed in the framework of the SO<sub>2</sub> Layer Height (S5P+I: SO<sub>2</sub> LH) project, which is part of ESA Sentinel-5p+ Innovation project (S5P+I). The S5P+I project aims to develop novel scientific and operational products to exploit the potential of the S5P/TROPOMI capabilities. The S5P+I: SO<sub>2</sub> LH project is dedicated to the generation of an SO<sub>2</sub> LH product and its extensive verification with collocated ground- and space-born measurements.</p>

A new method for mechanical testing of thin films: Application to aluminum

2009 ◽  
Vol 24 (4) ◽  
pp. 1353-1360
Author(s):  
T. Kruml ◽  
M. Stranyanek ◽  
R. Ctvrtlik ◽  
P. Bohac ◽  
T. Vystavel ◽  
...  
Keyword(s):  
Thin Films ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Accurate Determination ◽  
Film Surface ◽  
Strain Curve ◽  
New Method ◽  
Plastic Properties ◽  
Precise Knowledge

A new method for measuring plastic properties of thin films deposited on a substrate is presented. Micrometric cylindrical specimens with the axis perpendicular to the film surface were prepared by milling out the surrounding material using the focused ion beam technique. Such specimens were deformed by means of a nanoindenter outfitted with a flat diamond tip. An equivalent to the macroscopic compressive curve was obtained. Elastic modulus and hardness of the film were then measured using a Berkovich tip. The precise knowledge of the gage length and the independent measurement of elastic properties enable the accurate determination of the stress–strain curve. As compared with the results published in the literature on the specimens with the same dimensions, the studied material deforms less heterogeneously, probably as a consequence of the symmetric crystallographic orientation of the specimens.

scholarly journals I.—Eminent Living Geologists

1909 ◽  
Vol 6 (6) ◽  
pp. 241-250
Author(s):  
Ramsay Heatley Traquair
Keyword(s):  
Accurate Determination ◽  
Strict Sense ◽  
Precise Knowledge ◽  
Fossil Fish ◽  
Fish Remains

Many sciences contribute to the progress of geology, but none is more essential to it than that of zoology. The accurate determination of fossils, which can only be done by a trained systematic zoologist, is a necessity for stratigraphical work, and the broad questions of the geography of past ages can only be discussed with the aid of those who understand the distribution of life in the existing world. Dr. Traquair, the eminent ichthyologist of Edinburgh, though scarcely a geologist in the strict sense of the term, may therefore be claimed as one of the leaders in our science, for he has devoted more than forty years to the interpretation of fossil fish-remains, and so laid the foundations of a precise knowledge of extinct fishes which is as important to the stratigraphical geologist as to the biological philosopher.

scholarly journals MODELLING OF FORGETTING CURVES IN EDUCATIONAL E-ENVIRONMENT

2019 ◽  
Vol 71 (3) ◽  
pp. 1 ◽  
Author(s):  
Paweł Plaskura
Keyword(s):  
Differential Equations ◽  
Accurate Determination ◽  
Electrical Circuits ◽  
Variable Parameters ◽  
Time Constants ◽  
Behavioural Modelling ◽  
Generalized Variables ◽  
E Learning ◽  
Learning Platforms

Modelling of the didactical process by using educational network needs network representation of learning and forgetting curves known from the literature. The learning and forgetting curves are the solution of differential equations. The differential equations can be represented in the form of a network of connected elements in a similar way to the electrical circuits and represented in the form of an intuitive schematic. The network can be simulated using a microsystems simulator. Such an approach enables the easy creation of the macro models and their analysis. It enables the use of many advanced simulation algorithms. The use of analogy enables defining the educational environment by defining network variables and giving them meaning relative to generalized variables. In the paper, examples of representation of forgetting curves as the above-mentioned network are presented. Parameters of elements were selected in the deterministic optimisation process. The obtained results were compared with the forgetting curves known from the literature. The appropriate time constants were identified in the systems and their values were given. Time constants have their equivalents in the appropriate values in the formulas describing the forgetting curves. Based on the results, appropriate conclusions were drawn. The work also shows the concept of a model that uses behavioural modelling and variable parameters of elements depending on the state and time. The model has been used in practice. The presented approach enables a much more accurate determination of the parameters of the forgetting curves. The models can be used in the simulation of the forgetting process. The paper can be interesting for those who deal with modelling of the didactical process, especially on the e-learning platforms.

scholarly journals MATHEMATICAL MODELLING OF THE ANALYTICAL AND NUMERICAL SOLUTION OF NON-STATIONARY INITIAL-VALUE PROBLEMS BY MAPLE SOFTWARE.

2019 ◽  
pp. 87
Author(s):  
Iļja Sučkovs ◽  
Aleksandrs Pikurs ◽  
Ilmārs Kangro
Keyword(s):  
Differential Equations ◽  
Mathematical Modelling ◽  
Mathematical Models ◽  
Numerical Solution ◽  
Ordinary Differential Equations ◽  
Initial Value Problems ◽  
General Information ◽  
Radioactive Substance ◽  
Initial Value

With the passage of time and the development of technology, humanity is exploring new unknown problems that require complex analytical and numerical mathematical solutions. Due to their complexity differential equations are often used for this purpose. The aim of this work is to solve mathematical models of initial value problems of ordinary differential equations using the analitical method and numerical solution using MAPLE software. Also authors have provided general information about differential equations and diferent ways how they can be solved. As a result have been created two mathematical models which describe process of Determination of the cooling time of a shot animal and decomposition of the radioactive substance. Similar methods are also used to determine the age of objects as well

scholarly journals SO<sub>2</sub> Layer Height retrieval from Sentinel-5 Precursor/TROPOMI using FP_ILM

2019 ◽  
Author(s):  
Pascal Hedelt ◽  
Dmitry S. Efremenko ◽  
Diego G. Loyola ◽  
Robert Spurr ◽  
Lieven Clarisse
Keyword(s):  
Accurate Determination ◽  
Volcanic Eruptions ◽  
Critical Parameters ◽  
Retrieval Algorithm ◽  
Layer Height ◽  
Precise Knowledge ◽  
Learning Machine ◽  
The Impact ◽  
First Time

Abstract. Precise knowledge of the location and height of the volcanic SO2 plumes is essential for accurate determination of SO2 emitted by volcanic eruptions for aviation control applications, but so far very time-consuming to retrieve from UV satellite data. The SO2 height is furthermore one of the most critical parameters that determine the impact on the climate. We have developed an extremely fast yet accurate SO2 layer height retrieval algorithm using the Full-Physics Inverse Learning Machine (FP_ILM) algorithm, which, for the first time, is applied to TROPOMI aboard Sentinel-5 Precursor. In this work we demonstrate the ability of the FP_ILM algorithm to retrieve layer heights in near-real time applications with an accuracy of better than 2 km for SO2 total columns larger than 20 DU and show SO2 layer height results for selected volcanic eruptions.

scholarly journals A method of incorporating rate constants as kinetic constraints in molecular dynamics simulations

2020 ◽  
Vol 118 (2) ◽  
pp. e2012423118
Author(s):  
Z. Faidon Brotzakis ◽  
Michele Vendruscolo ◽  
Peter G. Bolhuis
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulations ◽  
Rate Constants ◽  
Molecular System ◽  
Accurate Determination ◽  
Molecular Simulations ◽  
Model Systems ◽  
Wide Range ◽  
Dynamics Simulations

From the point of view of statistical mechanics, a full characterization of a molecular system requires an accurate determination of its possible states, their populations, and the respective interconversion rates. Toward this goal, well-established methods increase the accuracy of molecular dynamics simulations by incorporating experimental information about states using structural restraints and about populations using thermodynamics restraints. However, it is still unclear how to include experimental knowledge about interconversion rates. Here, we introduce a method of imposing known rate constants as constraints in molecular dynamics simulations, which is based on a combination of the maximum-entropy and maximum-caliber principles. Starting from an existing ensemble of trajectories, obtained from either molecular dynamics or enhanced trajectory sampling, this method provides a minimally perturbed path distribution consistent with the kinetic constraints, as well as modified free energy and committor landscapes. We illustrate the application of the method to a series of model systems, including all-atom molecular simulations of protein folding. Our results show that by combining experimental rate constants and molecular dynamics simulations, this approach enables the determination of transition states, reaction mechanisms, and free energies. We anticipate that this method will extend the applicability of molecular simulations to kinetic studies in structural biology and that it will assist the development of force fields to reproduce kinetic and thermodynamic observables. Furthermore, this approach is generally applicable to a wide range of systems in biology, physics, chemistry, and material science.

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