scholarly journals First-order Kinetics in the Study of Enzymes: Applications to the Reporter Substrate Method and to the Estimation of kcat/Km

2020 ◽  
Vol 9 (3) ◽  
pp. 171-176
Author(s):  
Jean-Marie Frère ◽  
Olivier Verlaine
Keyword(s):  
Experimental Approach ◽  
Product Formation ◽  
Present Contribution ◽  
First Order ◽  
First Order Kinetics ◽  
Simple Program ◽  
Km Value ◽  
Total Absorbance ◽  
User Friendly

: The study of the interactions between enzymes and inactivators can often be performed with the help of the reporter substrate method in which the time-dependent decrease of the rate of substrate disappearance (or product formation) is monitored. In the present contribution, we wish to describe examples of the utilization of this rapid and efficient method for reactions whose rates can be monitored by spectrophotometric or fluorimetric measurements. After the collection of the data in an Excel file, a very simple program can be applied to extract the values of pseudo-- first-order rate constants. The inactivation can be complete or result in a steady-state if the inactivated adduct is not totally stable or if the inactivation reaction is reversible. Similarly, the method can be used in the cases of so-called “slow binding” inhibitors. The same type of analysis allows the easy determination of kcat/Km values for substrates for which the Km value is rather low. We show that this very rapid method (less than 5 min) yields very good values of the desired kinetic parameter even if the total absorbance variations are very low (0.1 or less). : In conclusion, the described experimental approach is particularly useful when applied to the reporter substrate method but it also allows the estimation of the kcat/Km parameter even if the Km value is rather low. : The authors wish to dedicate this paper to the memory of the late Michel Rinné (1941-2009) whose contribution to making the data analysis program very user-friendly was invaluable.

Modified ferron assay for speciation characterization of hydrolyzed Al(III): a precise k value based judgment

2009 ◽  
Vol 59 (4) ◽  
pp. 823-832 ◽  
Author(s):  
Ye Changqing ◽  
Wang Dongsheng ◽  
Wu Xiaohong ◽  
Qu Jiuhui ◽  
John Gregory
Keyword(s):  
Kinetic Constant ◽  
Nonlinear Least Squares ◽  
Precise Determination ◽  
K Value ◽  
First Order ◽  
First Order Kinetics ◽  
Parallel Reactions

The speciation of Al-OH complexes in terms of Ala, Alb and Alc could be achieved by traditional ferron assay and Alb is generally considered as Al13, however, the inherent correlation between them remains an enigma. This paper presents a modified ferron assay to get precise determination of Al13 using nonlinear least squares analysis, and to clarify the correlation between Alb and Al13. Two parallel reactions conforming to pseudo-first-order kinetics can simulate the complicate reactions between polynuclear complexes and ferron successfully. Four types of experimental kinetic constant (k value) of Al-OH complexes can be observed by this method when investigating three typical aluminium solutions. Comparing with the results of 27Al NMR, the species with moderate kinetics around 0.001 s−1 can be confirmed to resemble to Al13 polycation. The other types of kinetics are also well-regulated in partially neutralized aluminium solutions with various OH/Al ratios (b values) in the range 0 ∼ 2.5. It would provide potential means to trace the in-situ formation of Al13 in dilute solutions such as coagulation with Al-based coagulants

Effect of thiol oxidation and thiol export from erythrocytes on determination of redox status of homocysteine and other thiols in plasma from healthy subjects and patients with cerebral infarction

1995 ◽  
Vol 41 (3) ◽  
pp. 361-366 ◽  
Author(s):  
A Andersson ◽  
A Lindgren ◽  
B Hultberg
Keyword(s):  
Cerebral Infarction ◽  
Healthy Subjects ◽  
Redox Status ◽  
Reduced Form ◽  
Temperature Dependent ◽  
First Order ◽  
First Order Kinetics ◽  
Before And After ◽  
Reduced Forms

Abstract Changes in concentration of reduced and oxidized low-M(r) thiols were measured in blood and plasma before and after the separation of blood cells. If centrifugation of blood was postponed, the reduced form of homocysteine in plasma increased with time at 22 degrees C; in contrast, the concentrations of other reduced thiols (cysteine, glutathione, and cysteinylglycine) decreased. In plasma the reduced forms of all thiols disappeared at a rate that followed first-order kinetics. The rates of disappearance ("half-lives") were temperature-dependent; they were about the same for glutathione and homocysteine (11.7 and 14.3 min, respectively, at 22 degrees C) and somewhat higher for cysteinylglycine and cysteine. After establishing proper sampling conditions for reduced thiols, we measured this thiol fraction as well as free (non-protein-bound) and total thiols in 10 reference subjects and 19 patients with cerebral infarction. Mild but significant hyperhomocysteinemia involving total and free homocysteine (but not reduced homocysteine) was found in the patients.

scholarly journals Mineralization of sulfonamides from wastewater using ozone-based systems

2021 ◽  
Author(s):  
T. H. Ho ◽  
C. H. Wu ◽  
T. Y. Han ◽  
W. J. Syu
Keyword(s):  
Steric Hindrance ◽  
Radical Addition ◽  
The Novel ◽  
Mineralization Rate ◽  
First Order ◽  
First Order Kinetics ◽  
Pseudo First Order ◽  
Uv Ozone ◽  
Heterocyclic Group

Abstract Ozone, UV/ozone, ozone/persulfate (PS) and UV/ozone/PS systems were used to mineralize sulfonamides. Sulfadiazine (SDZ), sulfamerazine (SMR) and sulfamethazine (SMZ) were the target compounds. The novel contribution of this study is its determination of the effects of PS addition, sulfonamide structure, pH and salinity on sulfonamide mineralization in ozone-based systems. The mineralization rate of sulfonamides satisfied pseudo-first-order kinetics. The SMZ mineralization rate constant in ozone, UV/ozone, ozone/PS and UV/ozone/PS systems at pH 5 were 0.0058; 0.0101; 0.0069 and 0.0802 min−1, respectively, and those at pH 7 were 0.0075; 0.0116; 0.0083 and 0.0873 min−1, respectively. The increase in the number of methyl-substituents in the heterocyclic group of SMZ and the corresponding increase in the steric hindrance of radical addition, reduced mineralization rates below those of SMR and SDZ. The addition of PS promoted sulfonamide mineralization in the ozone-based systems; conversely, salinity inhibited sulfonamide mineralization.

scholarly journals ESTUDO DE ESTABILIDADE DO FOSFATO DISSÓDICO DE PREDNISOLONA EM CONDIÇÕES DE ESTRESSE OXIDATIVO E TÉRMICO, EM FORMULAÇÃO ORAL

2018 ◽  
Vol 35 (4) ◽  
pp. 09
Author(s):  
Cleber Antonio Lindino ◽  
Marcia Lina Mitsui ◽  
Rodolfo Ortiguara ◽  
Daiane Felin ◽  
Mauricio Ferreira Da Rosa ◽  
...  
Keyword(s):  
High Performance ◽  
Dosage Form ◽  
Degradation Products ◽  
Degradation Process ◽  
Oral Solution ◽  
Form Solution ◽  
Oral Dosage ◽  
First Order ◽  
First Order Kinetics

This work was to investigate the process of degradation of the drug Prednisolone Sodium Phosphate (FSP) in oral solution dosage form through the degradation experiments, evaluating the parameters in accordance with Resolution 899/2003 ANVISA and the degradation process of the drug. The method by high performance liquid chromatography (HPLC) developed for the determination of the drug was validated to demonstrate its applicability as an indicator of stability, ensuring reliability. After the method be validated to study the degradation of the drug, it was shown that drastic conditions of oxidative stress (H O 30%) and 2 2 temperature 60°C, the degradation of the drug is dependent on its concentration (first order kinetics). The results were  satisfactory, showing that this method is suitable to investigate the formation of degradation products in oral dosage form solution

scholarly journals Determination of Ozone or Hypochlorite in Waters Based on Digital Images Analysis Using Same Reagent

2021 ◽  
Author(s):  
Lorrayne Zampier ◽  
André Fernando de Oliveira ◽  
Fernanda Heleno ◽  
Maria Eliana de Queiroz ◽  
Antônio Augusto Neves ◽  
...  
Keyword(s):  
Digital Image Analysis ◽  
Digital Images ◽  
First Order ◽  
Figures Of Merit ◽  
Malachite Green Dye ◽  
First Order Kinetics ◽  
The Subject ◽  
Different Response ◽  
Analytical Resolution

Ozone and hypochlorite are used for the disinfection of water and is essential to monitor these. In this paper, methods based on digital images were developed to determine these analytes in waters using the malachite green dye. The oxidation of the reagent with ozone was very fast and with hypochlorite occurred in 10 min in pseudo-first-order kinetics. New software called ICCA was developed for the capture and processing of red, green and blue (RGB) data, which is planned for digital image analysis. In addition, the recently proposed parameters analytical resolution and N9 were used to define some study conditions. An evaluation of different response functions and white correction of the webcam were done, having thrown some light on the subject to this theme. Their optimization showed a linear range from 0.6 mg L-1 to 5.0/6.0 mg L-1 (O3/Cl, respectively). The figures of merit were similar for both. The methods were validated and the recoveries achieved were between 85.0 and 96.0% (ozone) and 101.0 and 119.0% (hypochlorite).

scholarly journals A KINETIC ANALYSIS OF THE RENIN-ANGIOTONIN PRESSOR SYSTEM AND THE STANDARDIZATION OF THE ENZYMES RENIN AND ANGIOTONASE

1943 ◽  
Vol 78 (5) ◽  
pp. 367-386 ◽  
Author(s):  
Albert A. Plentl ◽  
Irvine H. Page
Keyword(s):  
Pressor Response ◽  
Accurate Method ◽  
Enzyme Concentration ◽  
Renin Substrate ◽  
First Order ◽  
First Order Kinetics ◽  
Consecutive Reactions ◽  
Slow Decline ◽  
Reaction Constant

The physicochemical background of the renal vasporessor system (renin-renin-substrate, angiotinin, angiotonase) is given. The formation and destruction of angiotonin is shown to consist of two consecutive reactions, both of which follow the laws of first order kinetics. Each reaction was studied separately and its reaction constant found to be proportional to the enzyme concentration. Hence these constants should be used to express the activity of the enzymes, renin and angiotonase. The over-all reaction of a mixture of renin and angiotonase such as occurs in kidney extracts with the α-globulin fraction of serum, viz., rapid increase followed by a slow decline in angiotonin concentration, was found experimentally to correspond closely to the theoretical values calculated for such a reaction. The curve obtained also satisfyingly explains the characteristic pressor response to the intravenous injection of renin. An accurate method for the determination of renin in the presence of angiotonase is presented.

On the determination of the frequency factor in the thermally stimulated luminescence with non-first-order kinetics

1996 ◽  
Vol 69 (3) ◽  
pp. 175-177 ◽  
Author(s):  
S.Dorendrajit Singh ◽  
E.Dwijamani Singh ◽  
N.C. Deb ◽  
S.C. Mukherjee ◽  
P.S. Mazumdar
Keyword(s):  
Frequency Factor ◽  
Thermally Stimulated Luminescence ◽  
First Order ◽  
First Order Kinetics

scholarly journals Determination of Chemical Stability of Two Oral Antidiabetics, Metformin and Repaglinide in the Solid State and Solutions Using LC-UV, LC-MS, and FT-IR Methods

Molecules ◽  
2019 ◽  
Vol 24 (24) ◽  
pp. 4430
Author(s):  
Anna Gumieniczek ◽  
Anna Berecka-Rycerz ◽  
Tomasz Mroczek ◽  
Krzysztof Wojtanowski
Keyword(s):  
High Temperature ◽  
Degradation Products ◽  
Degradation Kinetics ◽  
Magnesium Stearate ◽  
Oral Antidiabetics ◽  
First Order ◽  
First Order Kinetics ◽  
Ft Ir ◽  
The Stability

Firstly, metformin and repaglinide were degraded under high temperature/humidity, UV/VIS light, in different pH and oxidative conditions. Secondly, a new validated LC-UV method was examined, as to whether it validly determined these drugs in the presence of their degradation products and whether it is suitable for estimating degradation kinetics. Finally, the respective LC-MS method was used to identify the degradation products. In addition, using FT-IR method, the stability of metformin and repaglinide was scrutinized in the presence of polyvinylpyrrolidone (PVP), mannitol, magnesium stearate, and lactose. Significant degradation of metformin, following the first order kinetics, was observed in alkaline medium. In the case of repaglinide, the most significant and quickest degradation, following the first order kinetics, was observed in acidic and oxidative media (0.1 M HCl and 3% H2O2). Two new degradation products of metformin and nine new degradation products of repaglinide were detected and identified when the stressed samples were examined by our LC-MS method. What is more, the presence of PVP, mannitol, and magnesium stearate proved to affect the stability of metformin, while repaglinide stability was affected in the presence of PVP and magnesium stearate.

scholarly journals Exploring the scope of DBU-promoted amidations of 7-methoxycarbonylpterin

2020 ◽  
Vol 16 ◽  
pp. 509-514 ◽  
Author(s):  
Anna R Bockman ◽  
Jeffrey M Pruet
Keyword(s):  
Reaction Kinetics ◽  
Structural Features ◽  
Product Formation ◽  
Reaction Conditions ◽  
First Order ◽  
First Order Kinetics ◽  
Synthetic Utility ◽  
Pseudo First Order ◽  
Pteridine Derivatives

The synthetic utility of pterins is often hampered by the notorious insolubility of this heterocycle, slowing the development of medicinally relevant pteridine derivatives. Reactions which expedite the development of new pterins are thus of great importance. Through a dual role of diazabicycloundecene (DBU), 7-carboxymethylpterin is converted to the soluble DBU salt, with additional DBU promoting an ester-to-amide transformation. We have explored this reaction to assess its scope and identify structural features in the amines which significantly affect success, monitored the reaction kinetics using a pseudo-first order kinetics model, and further adapted the reaction conditions to allow for product formation in as little as 5 min, with yields often >80%.

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