Sweeping Capillary Electrophoresis:  A Non-Stopped-Flow Method for Measuring Bimolecular Rate Constant of Complex Formation between Protein and DNA

2004 ◽  
Vol 126 (23) ◽  
pp. 7166-7167 ◽  
Author(s):  
Victor Okhonin ◽  
Maxim Berezovski ◽  
Sergey N. Krylov
Keyword(s):  
Capillary Electrophoresis ◽  
Complex Formation ◽  
Rate Constant ◽  
Stopped Flow ◽  
Flow Method ◽  
Bimolecular Rate Constant

scholarly journals KINETIC STUDY ON ANIONIC σ-COMPLEX FORMATION BETWEEN 2,4,6-TRINITROANISOLE AND METHOXIDE ION BY HIGH PRESSURE STOPPED-FLOW METHOD

1979 ◽  
Vol 8 (6) ◽  
pp. 671-674 ◽  
Author(s):  
Noboru Takisawa ◽  
Muneo Sasaki ◽  
Fujitsugu Amita ◽  
Jiro Osugi
Keyword(s):  
High Pressure ◽  
Complex Formation ◽  
Kinetic Study ◽  
Stopped Flow ◽  
Flow Method ◽  
Methoxide Ion

Kinetic Studies on the ES-complex Formation of p-Hydroxybenzoate Hydroxylase Using the Stopped-flow Method

1970 ◽  
Vol 67 (5) ◽  
pp. 749-752 ◽  
Author(s):  
NAOKI HIGASHI ◽  
HIROHUMI SHOUN ◽  
KEITARO HIROMI ◽  
KEIJI YANO ◽  
KEI ARIMA
Keyword(s):  
Complex Formation ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Flow Method ◽  
Hydroxybenzoate Hydroxylase

Etude du système acridine orange – poly(C) et de son interaction avec les complexes du palladium(II)

1984 ◽  
Vol 62 (9) ◽  
pp. 1681-1686 ◽  
Author(s):  
Robert Ménard ◽  
Miklos Zador
Keyword(s):  
Acridine Orange ◽  
Thermodynamic Parameters ◽  
Rate Constant ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Flow Method ◽  
Polycytidylic Acid ◽  
Low Concentrations ◽  
C Complex ◽  
Kinetics Of

The complex formed between acridine orange (AO) and polycytidylic acid (poly(C)) was studied by spectrophotometry and spectrofluorometry. The complex was characterized by its stoichiometry, structure, and the thermodynamic parameters of its formation. The results are in agreement with an external aggregation of the protonated dye along the negatively charged poly(C) chain and indicate that approximately two AO molecules are bound per nucleotide unit of poly(C). The kinetics of the reaction between this complex and a Pd(II) complex was studied by the stopped-flow method. The addition of (dien)Pd(II) to the AO–poly(C) complex leads to the dissociation of the latter, due to fixation of the Pd(II) complex to the N3 site of the cytosine base of poly(C). The rate constant for the AO liberation, extrapolated at zero AO concentration, corresponds to the rate constant of Pd(II) fixation on poly(C). This indicates that AO can be used as an indicator for this reaction and allows kinetic studies at very low concentrations (≤ 5 × 10−6 M).

scholarly journals Stopped-Flow Spectrophotometric Studies of the Kinetics of Interaction of Dihydroxyfumaric Acid with the DPPH Free Radical

2010 ◽  
Vol 5 (2) ◽  
pp. 83-87
Author(s):  
Natalia Secara
Keyword(s):  
Free Radical ◽  
Reaction Kinetics ◽  
Rate Constant ◽  
Stopped Flow ◽  
Flow Method ◽  
Reaction Proceeds ◽  
Reaction Orders ◽  
Stoichiometric Reaction ◽  
Two Stages ◽  
Kinetics Of

The reaction of dihydroxyfumaric acid with the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH) was studied using the stopped-flow method, in order to describe the reaction kinetics. Dihydroxyfumaric acid reacts very rapidly with DPPH, the reaction being completed in several minutes. This 2-stoichiometric reaction proceeds in two stages, with reaction orders of 1 and 0.76 with respect to DPPH, and 0.5 and 0.3 with respect to DHF, respectively. The rate constant of the two stages of the reaction were found to be 39.1 (L/mol•s) and 0.0012 (s-1) at 20º C and pH 4.0.

Formation of CT complexes and electron transfer from excited molecules of anthracene derivatives to methylviologen in aqueous and micellar media

1987 ◽  
Vol 52 (7) ◽  
pp. 1658-1665
Author(s):  
Viktor Řehák ◽  
Jana Boledovičová
Keyword(s):  
Electron Transfer ◽  
Complex Formation ◽  
Fluorescence Quenching ◽  
Rate Constant ◽  
Formation Constants ◽  
Dynamic Quenching ◽  
Micellar Media ◽  
Complex Formation Constants ◽  
Anthracene Derivatives ◽  
Ct Complexes

Disodium 1,5- and 1,8-anthracenedisulphonate (ADS) and 9-acetylanthracene form coloured CT complexes with methylviologen (MV2+) in aqueous and micellar media. The complex formation constants and molar absorptivities were determined by the Benesi-Hildebrandt method. In the fluorescence quenching, its static component plays the major role. The dynamic quenching component is determined by the rate constant of electron transfer from the S1 state of ADS to MV2+.

Combined electrolysis—stopped flow method (SFEL)

1991 ◽  
Vol 302 (1-2) ◽  
pp. 285-291 ◽  
Author(s):  
V.G. Mairanovsky ◽  
S.Kh. Samvelyan
Keyword(s):  
Stopped Flow ◽  
Flow Method

A stopped-flow/continuous-flow method for kinetic determinations

1995 ◽  
Vol 309 (1-3) ◽  
pp. 277-282 ◽  
Author(s):  
Yun-Sheng Hsieh ◽  
S.R. Crouch
Keyword(s):  
Continuous Flow ◽  
Stopped Flow ◽  
Flow Method ◽  
Continuous Flow Method

From Reduction to Oxidation: pH Controlled Reaction of 1 Hydroxyethyl Radical with Caffeic Acid Analogues.

2021 ◽  
Vol 11 ◽  
Author(s):  
Laboni Das ◽  
Shashi P Shukla ◽  
Suchandra Chatterjee ◽  
Ashis K Satpati ◽  
Soumyakanti Adhikari
Keyword(s):  
Caffeic Acid ◽  
Rate Constant ◽  
Reduction Process ◽  
Phenoxyl Radical ◽  
Alpha Tocopherol ◽  
Side Chain ◽  
Product Analysis ◽  
Bimolecular Rate Constant ◽  
Ethyl Radical ◽  
Computational Calculations

Aims: The aim is to search for newer and better antioxidants through kinetic spectroscopic studies in combination with product analysis and computation. Background: Antioxidant effect of caffeic acid, its derivative, and analogues have been well reported. The antioxidative efficiencies are related to their molecular structure, and two reaction pathways are well accepted, H-atom transfer (HAT) or single electron transfer. 1-hydroxy ethyl radical (1-HER) being an ethanol-derived free radical might be causing the onset of liver injury detected after alcohol administration. 1-HER has also been reported to react with fatty acids and endogenous antioxidants such as glutathione, ascorbic acid, and alpha-tocopherol Objective: The present study is an attempt to understand the reaction mechanism of 1-HER with caffeic acid, its derivative, and analogues in detail. Method: Pulse radiolysis with kinetic absorption spectroscopy has been employed to follow the reaction pathway and identify the intermediates produced in the reaction. The reaction products have been detected using LCMS/MS. Based on these studies, a consolidated mechanism has been proposed. Cyclic voltammetry measurements and computational calculations have been used in support of the proposed mechanism. Result: In the reaction of 1-hydroxy ethyl radical (1-HER) with caffeic acid and its oligomers, reduction takes place below the pKa1, while oxidation occurs with the deprotonated phenolic moiety. The reduction of caffeic acid generates a carbon-centered radical at the double bond of the side chain with a bimolecular rate constant of 1.5x1010 dm3 mol-1 s-1. Notably, a low concentration of oxygen was able to regenerate a part of the caffeic acid molecules in the reduction process. At pH 10 a phenoxyl radical is formed due to oxidation with a much lower bimolecular rate constant (4.2x108 dm3 mol-1 s-1). In the case of di-hydrocaffeic acid, only phenoxyl radical is formed at pH 10 and, no reaction could be observed below pH 8. Conclusion: Change in reactive pattern from reduction to oxidation with change in pH within the same set of reactants has been evidently established in the present study. The results point towards the importance of  unsaturation in the side chain of caffeic acid oligomers for their reaction with 1-HER at neutral pH. The effect of oxygen concentration on the antioxidative protection offered by this class of molecules might be intriguing for the quest of the effectiveness of antioxidants at low concentrations. Other: It may be inferred that the effect of pH on the reactivity pattern as observed is not 1-HER, but substrate-specific, in the present case, phenolic acids. This study generates further scope for in-depth studies on other polyphenols where unsaturation exists in the side chain.

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