scholarly journals Phase-Plane Geometries in Coupled Enzyme Assays

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Wylie Stroberg ◽  
Santiago Schnell
Keyword(s):  
Time Course ◽  
Vector Fields ◽  
Phase Plane ◽  
Dynamical Behavior ◽  
Enzymatic Reaction ◽  
Geometric Interpretation ◽  
Slow Manifolds ◽  
Singular Perturbation Analysis ◽  
Kinetics Of

The determination of a substrate or enzyme activity by coupling of one enzymatic reaction with another easily detectable (indicator) reaction is a common practice in the biochemical sciences. Usually, the kinetics of enzyme reactions is simplified with singular perturbation analysis to derive rate or time course expressions valid under the quasi-steady-state and reactant stationary state assumptions. In this paper, the dynamical behavior of coupled enzyme catalyzed reaction mechanisms is studied by analysis of the phase-plane. We analyze two types of time-dependent slow manifolds - Sisyphus and Laelaps manifolds - that occur in the asymptotically autonomous vector fields that arise from enzyme coupled reactions. Projection onto slow manifolds yields various reduced models, and we present a geometric interpretation of the slow/fast dynamics that occur in the phase-planes of these reactions. <br>

Phase-Plane Geometries in Coupled Enzyme Assays

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Wylie Stroberg ◽  
Santiago Schnell
Keyword(s):  
Time Course ◽  
Vector Fields ◽  
Phase Plane ◽  
Dynamical Behavior ◽  
Enzymatic Reaction ◽  
Geometric Interpretation ◽  
Slow Manifolds ◽  
Singular Perturbation Analysis ◽  
Kinetics Of

The determination of a substrate or enzyme activity by coupling of one enzymatic reaction with another easily detectable (indicator) reaction is a common practice in the biochemical sciences. Usually, the kinetics of enzyme reactions is simplified with singular perturbation analysis to derive rate or time course expressions valid under the quasi-steady-state and reactant stationary state assumptions. In this paper, the dynamical behavior of coupled enzyme catalyzed reaction mechanisms is studied by analysis of the phase-plane. We analyze two types of time-dependent slow manifolds - Sisyphus and Laelaps manifolds - that occur in the asymptotically autonomous vector fields that arise from enzyme coupled reactions. Projection onto slow manifolds yields various reduced models, and we present a geometric interpretation of the slow/fast dynamics that occur in the phase-planes of these reactions. <br>

Phase-Plane Geometries in Coupled Enzyme Assays

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Wylie Stroberg ◽  
Santiago Schnell
Keyword(s):  
Time Course ◽  
Vector Fields ◽  
Phase Plane ◽  
Dynamical Behavior ◽  
Enzymatic Reaction ◽  
Enzyme Assays ◽  
Mathematical Framework ◽  
Indicator Reaction ◽  
Slow Manifolds ◽  
Singular Perturbation Analysis

The determination of a substrate or enzyme activity by coupling of one enzymatic reaction with another easily detectable (indicator) reaction is a common practice in the biochemical sciences. The dynamical behavior of couple enzyme catalyzed assays is studied by analysis in the phase plane. Usually, the kinetics of enzyme reactions is simplified with singular perturbation analysis to derive rate or time course expressions valid under the quasi-steady-state and reactant stationary state assumptions. In this paper, we analyze two types of time-dependent slow manifolds that occur in asymptotically autonomous vector fields that arise from enzyme coupled assays. We show that the motion of the slow manifolds relative to the motion of the solution must be taken into account in order to formulate accurate leading order asymptotic solutions. We also develop a rigorous mathematical framework from which to analyze enzyme catalyzed indicator reaction from couple enzyme assays.

scholarly journals Phase-Plane Geometries in Coupled Enzyme Assays

2018 ◽  
Author(s):  
Justin Eilertsen ◽  
Wylie Stroberg ◽  
Santiago Schnell
Keyword(s):  
Time Course ◽  
Vector Fields ◽  
Phase Plane ◽  
Dynamical Behavior ◽  
Enzymatic Reaction ◽  
Accurate Estimation ◽  
Enzyme Assays ◽  
Phase Plane Analysis ◽  
Mathematical Framework ◽  
Slow Manifolds

<div>The determination of a substrate or enzyme activity by coupling of one enzymatic reaction with another easily detectable (indicator) reaction is a common practice in the biochemical sciences. Usually, the kinetics of enzyme reactions is simplified with singular perturbation analysis to derive rate or time course expressions valid under the quasi-steady-state and reactant stationary state assumptions. In this paper, the dynamical behavior of coupled enzyme catalyzed assays is studied by analysis in the phase plane. We analyze two types of time-dependent slow manifolds - Sisyphus and Laelaps manifolds - that occur in asymptotically autonomous vector fields that arise from enzyme coupled assays. Projection onto slow manifolds yields various reduced models, and we develop a mathematical framework from which to analyze coupled enzyme assays through scaling and phase-plane analysis. We demonstrate the necessity of fast indicator reactions to derive mathematical expressions which could be used for the accurate estimation of enzyme kinetic parameters through experimental assays in the laboratory.</div>

scholarly journals In Vitro Evaluation of the Sensitivity of a Hyaluronic Acid PEG Cross-Linked to Bovine Testes Hyaluronidase

2018 ◽  
Vol 6 (1) ◽  
pp. 20-24 ◽  
Author(s):  
Nicola Zerbinati ◽  
Torello Lotti ◽  
Damiano Monticelli ◽  
Virginia Martina ◽  
Giovanna Cipolla ◽  
...  
Keyword(s):  
Hyaluronic Acid ◽  
Soft Tissue ◽  
Chemical Reaction ◽  
Time Course ◽  
Soft Tissue Augmentation ◽  
Facial Soft Tissue ◽  
Microplate Reader ◽  
Kinetics Of

Neauvia Intense is biocompatible, injectable hyaluronic acid (HA) filler PEG cross-linked for facial soft-tissue augmentation that provides volume to tissues. The aim of the present study is to evaluate the sensitivity of Neauvia Intense in hyaluronidase from bovine testes in a time-course analysis. The test is based on the colourimetric determination of the N-acetyl – D - glucosamine (NAG) released by the hyaluronidase in standardised conditions. The in vitro conditions involve the treatment of Neauvia Intense with a known concentration of the enzyme (6080U/ml). The NAG content was determined at different times to assess the kinetics of the degradation (1h, 3h, 6h, 24h, 48h, 72h, 120h, and 168h); the Ehrlich’s reagent was used for the colourimetric quantification, by the method described by Reissing and colleagues. The intensity of the violet colour developed after the chemical reaction was proportional to the NAG present in each sample. A microplate reader at 585 nm read the absorbance. The amount of NAG released by the product was proportional to the time of incubation with bovine hyaluronidase, reaching a plateau after 168 hours.

Reactive Diffusion upon Planar Dissolving Copper in Solder Melts

2011 ◽  
Vol 309-310 ◽  
pp. 127-134 ◽  
Author(s):  
Jaromír Drápala ◽  
Pavel Jopek ◽  
Daniel Petlák ◽  
Petr Harcuba ◽  
Petr Kubíček
Keyword(s):  
Interphase Boundary ◽  
Time Course ◽  
Solid Phase ◽  
Accurate Determination ◽  
Theoretical Description ◽  
Reactive Diffusion ◽  
Boundary Movement ◽  
Original Metal ◽  
Kinetics Of

Problems of reactive diffusion at a solid phase - melt contact were studied theoretically. The main intention was to calculate the time course of the solid phase dissolving in the case of planar dissolving. In our work we give heed especially to the dominating process, which is the solid metal A dissolving in solder melt B. During the dissolving, melt B saturates with metal A, and the process is influenced by convections which are characteristic for a given experimental configuration. A theoretical description of the kinetics of solid phase dissolving in the melt will be presented for the case of planar dissolving. The aim is to derive a relation for the interphase boundary movement (t) depending on time and a time course of growth of the element A concentration in the melt B. There are difficulties in accurate determination of the interphase boundary movement after heating of specimens for certain time intervals. It should be performed experimentally, since intermetallic phases are formed in original metal A both via diffusion and upon cooling and some phases segregate upon cooling of the solidifying melt. The main intention was to study experimentally the copper dissolving in melts of various solder alloys and the related reactive diffusion. We used pure Sn and Sn-Cu, Sn-Ag-Cu, Sn-Sb, Sn-Zn alloys as solder materials. Experiments aimed at the study of a Cu plate dissolving in the solder melt were carried out at various selected temperatures and times. The problems of reactive diffusion were studied both theoretically and experimentally and the problems that have to be solved preferably were emphasized. Concentration profiles of elements and thickness of layers of phases can be determined with SEM and X-ray microanalyses (WDX, EDX) of specimens after their diffusion heating.

Influence of Radioiodine Therapy on Urinary Iodine Excretion

1998 ◽  
Vol 37 (03) ◽  
pp. 107-112 ◽  
Author(s):  
I. Lauer ◽  
M. Bähre ◽  
E. Richter ◽  
B. Melier
Keyword(s):  
Time Course ◽  
Radioiodine Therapy ◽  
Urinary Iodine ◽  
Target Volume ◽  
Urinary Iodine Excretion ◽  
Urinary Creatinine ◽  
Iodine Excretion ◽  
Kinetics Of ◽  
Persistent Elevation ◽  
Benign Thyroid

Summary Aim: In 214 patients with benign thyroid diseases the time-course of urinary iodine excretion (UIE) was investigated in order to identify changes after radioiodine therapy (RITh). Method: UIE was measured photometrically (cerium-arsenite method) and related to urinary creatinine on the first and last day of the radioiodine test and then three days, seven days, four weeks, and six months after 1311 administration. Results: As compared with the level found immediately before radioiodine therapy, median UIE had almost doubled four weeks after therapy and was still significantly elevated six months after therapy. This increase correlated significantly with the target volume as measured by scintigraphy and sonography. Conclusions: The persistent elevation of UIE for months after RITh is a measure of treatment-induced damage to thyrocytes. Therefore, in view of the unfavourable kinetics of iodine that follow it, RITh should if possible be given via a single-dose regime.

Determination of microbiological activity during the processing of frost damaged sugar beets

2014 ◽  
pp. 228-231 ◽  
Author(s):  
Maciej Wojtczak ◽  
Aneta Antczak-Chrobot ◽  
Edyta Chmal-Fudali ◽  
Agnieszka Papiewska
Keyword(s):  
Sugar Beet ◽  
Microbiological Activity ◽  
Microbiological Contamination ◽  
Sugar Beets ◽  
Bacterial Metabolites ◽  
Kinetics Of

The aim of the study is to evaluate the kinetics of the synthesis of dextran and other bacterial metabolites as markers of microbiological contamination of sugar beet.

Studies on the Behavior Some Paints in Electro-insulating Fluid Based on Vegetable Esters

2018 ◽  
Vol 69 (5) ◽  
pp. 1139-1144
Author(s):  
Iosif Lingvay ◽  
Adriana Mariana Bors ◽  
Livia Carmen Ungureanu ◽  
Valerica Stanoi ◽  
Traian Rus
Keyword(s):  
Structural Changes ◽  
Oxidation Processes ◽  
High Oleic ◽  
Painting Materials ◽  
Insulating Paper ◽  
Different Types ◽  
Mechanism And Kinetics ◽  
Kinetics Of ◽  
Natural Ester

For the purpose of using three different types of painting materials for the inner protection of the transformer vats, their behavior was studied under actual conditions of operation in the transformer (thermal stress in electro-insulating fluid based on the natural ester in contact with copper for electro-technical use and electro-insulating paper). By comparing determination of the content in furans products (HPLC technique) and gases formed (by gas-chromatography) in the electro-insulating fluid (natural ester with high oleic content) thermally aged at 130 �C to 1000 hours in closed glass vessels, it have been found that the presence the investigated painting materials lead to a change in the mechanism and kinetics of the thermo-oxidation processes. These changes are supported by oxygen dissolved in oil, what leads to decrease both to gases formation CO2, CO, H2, CH4, C2H4 and C2H6) and furans products (5-HMF, 2-FOL, 2 -FAL and 2-ACF). The painting materials investigated during the heat treatment applied did not suffer any remarkable structural changes affecting their functionality in the electro-insulating fluid based on vegetable esters.

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