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.

A Stirred-Flow Reactor for Investigating the Kinetics of Gaseous Reactions: Application to the Decomposition of Di-t-butyl Peroxide

1961 ◽  
Vol 14 (4) ◽  
pp. 534 ◽  
Author(s):  
MFR Mulcahy ◽  
DJ Williams
Keyword(s):  
Excellent Agreement ◽  
Rate Constant ◽  
Flow Reactor ◽  
Reaction Times ◽  
Static Method ◽  
Flow Conditions ◽  
Gaseous Reaction ◽  
Flow Method ◽  
Butyl Peroxide ◽  
Kinetics Of

The uncertainty regarding temperature and flow conditions which attaches to the conventional flow method of determining the rate of a gaseous reaction can be substantially reduced by using a stirred-flow reactor. The reagents, products, and carrier-gas (if any) are mixed sufficiently vigorously for the composition of the gas in the reactor to be virtually uniform. A reactor designed to achieve the required degree of mixing at pressures of about 1 cmHg and reaction times of the order of 1 sec to 1 min is described. The rate constant of the decomposition of di-t-butyl peroxide was determined over the temperature range 430-550 �K. The values derived on the assumption of complete mixing in the reactor were independent of the degree of conversion and in excellent agreement with those obtained by previous authors using the static method.

scholarly journals Kinetic Studies of the Interaction of Toluidine Blue with Poly-(αL-glutamic acid) by Means of Stopped-Flow Method

1978 ◽  
Vol 10 (2) ◽  
pp. 153-159 ◽  
Author(s):  
Hidetoshi Ushio ◽  
Hiroshi Uchimura ◽  
Yoshikuni Tsuji ◽  
Takayuki Sano ◽  
Tatsuya Yasunaga
Keyword(s):  
Glutamic Acid ◽  
Toluidine Blue ◽  
Kinetic Studies ◽  
Stopped Flow ◽  
Flow Method

KINETIC STUDIES ON THE HYDROLYSIS OF BENZOYLCHOLINE BY HUMAN SERUM CHOLINESTERASE

1956 ◽  
Vol 34 (1) ◽  
pp. 637-653 ◽  
Author(s):  
W. Kalow ◽  
K. Genest ◽  
N. Staron
Keyword(s):  
Kinetic Studies ◽  
Reaction Rates ◽  
Serum Cholinesterase ◽  
Initial Reaction ◽  
Ultraviolet Spectrophotometry ◽  
First Order ◽  
Low Concentrations ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Substrate Concentrations

Benzoylcholine stands out from other known substrates of serum cholinesterase because of its high apparent affinity for this enzyme combined with a rapid rate of destruction. The reaction kinetics of the hydrolysis of benzoylcholine can be studied by ultraviolet spectrophotometry, since the absorbance decreases in proportion to the concentration of substrate. Kinetic data obtained by measuring initial reaction rates, and by analyzing continuous hydrolysis curves, are the same within the range of experimental error. The enzymatic data are compatible with the assumption that in the presence of high substrate concentrations a complex consisting of esterase and two substrate molecules is formed. This complex is hydrolyzed more slowly than the complex containing one molecule of substrate which is formed at low concentrations of benzoylcholine. Alkaline hydrolysis of benzoylcholine follows the kinetics of a first order reaction.

Mechanism of bromination of a quaternary pyrimidinium cation. Change of rate determining step with acidity

1978 ◽  
Vol 56 (23) ◽  
pp. 2970-2976 ◽  
Author(s):  
Oswald S. Tee ◽  
David C. Thackray ◽  
Charles G. Berks
Keyword(s):  
Kinetic Study ◽  
Rate Constants ◽  
Aqueous Media ◽  
Stopped Flow ◽  
Flow Method ◽  
High Acidity ◽  
Rate Determining Step ◽  
Kinetics Of ◽  
Good Agreement

The kinetics of bromination of the 1,2-dihydro-1,3-dimethyl-2-oxopyrimidinium cation (Q+) in aqueous media (pH 0–5) have been studied using the stopped-flow method. At the higher acidities (pH < 2) the results are consistent with rate determining attack by bromine upon the pseudobase (QOH), whereas at low acidities (pH > 4) it appears that pseudobase formation is rate determining. The change occurs because at high acidity the reversal of the pseudobase QOH to the cation is fast relative to bromine attack, whereas at low acidity the converse is true. Results obtained at intermediate acidities (pH 2–4) are consistent with this interpretation.A separate kinetic study of pseudobase formation (and decomposition) yielded rate constants in good agreement with those derived from the bromination study.

Etude cinétique des systèmes Cu(II)•Adénosine et Cu(II)•D-Ribose

1972 ◽  
Vol 50 (19) ◽  
pp. 3117-3123 ◽  
Author(s):  
G. Boivin ◽  
M. Zador
Keyword(s):  
Kinetic Parameters ◽  
Acidic Medium ◽  
Temperature Jump ◽  
Strong Acid ◽  
Basic Medium ◽  
Stopped Flow ◽  
Acid Solutions ◽  
Flow Method ◽  
Kinetics Of ◽  
Adenine Base

The kinetics of the formation and dissociation of Cu(II) complexes of adenosine have been determined in acidic and basic medium. In acidic medium, the complex is formed between the Cu(II) and the adenine base and the kinetic parameters have been obtained in this case using a temperature jump method. In basic medium, only the dissociation of the complexes could be studied by a stopped-flow method, by addition of EDTA or strong acid solutions. In these complexes, Cu(II) is bridged with ribose hydroxyls. Finally, D-ribose has also been studied for comparison in the same conditions. The mechanism of these reactions is discussed.

Sign in / Sign up

Export Citation Format

Share Document