Inhibition of the elastase of Pseudomonas aeruginosa by N.alpha.-phosphoryl dipeptides and kinetics of spontaneous hydrolysis of the inhibitors

Biochemistry ◽  
1984 ◽  
Vol 23 (12) ◽  
pp. 2766-2772 ◽  
Author(s):  
Louis Poncz ◽  
Thomas A. Gerken ◽  
Dorr G. Dearborn ◽  
Damian Grobelny ◽  
Richard E. Galardy
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Spontaneous Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

scholarly journals Colistin Methanesulfonate Is an Inactive Prodrug of Colistin against Pseudomonas aeruginosa

2006 ◽  
Vol 50 (6) ◽  
pp. 1953-1958 ◽  
Author(s):  
Phillip J. Bergen ◽  
Jian Li ◽  
Craig R. Rayner ◽  
Roger L. Nation
Keyword(s):  
Pseudomonas Aeruginosa ◽  
High Performance ◽  
Time Course ◽  
Antimicrobial Activities ◽  
Killing Effect ◽  
Time Profiles ◽  
Concentration Time ◽  
Colistin Methanesulfonate ◽  
Kinetics Of ◽  
Hydrolysis Of

ABSTRACT There is a dearth of information on the pharmacodynamics of “colistin,” despite its increasing use as a last line of defense for treatment of infections caused by multidrug-resistant gram-negative organisms. The antimicrobial activities of colistin and colistin methanesulfonate (CMS) were investigated by studying the time-kill kinetics of each against a type culture of Pseudomonas aeruginosa in cation-adjusted Mueller-Hinton broth. The appearance of colistin from CMS spiked at 8.0 and 32 mg/liter was measured by high-performance liquid chromatography, which generated colistin concentration-time profiles. These concentration-time profiles were subsequently mimicked in other incubations, independent of CMS, by incrementally spiking colistin. When the cultures were spiked with CMS at either concentration, there was a substantial delay in the onset of the killing effect which was not evident until the concentrations of colistin generated from the hydrolysis of CMS had reached approximately 0.5 to 1 mg/liter (i.e., ∼0.5 to 1 times the MIC for colistin). The time course of the killing effect was similar when colistin was added incrementally to achieve the same colistin concentration-time course observed from the hydrolysis of CMS. Given that the killing kinetics of CMS can be accounted for by the appearance of colistin, CMS is an inactive prodrug of colistin with activity against P. aeruginosa. This is the first study to demonstrate the formation of colistin in microbiological media containing CMS and to demonstrate that CMS is an inactive prodrug of colistin. These findings have important implications for susceptibility testing involving “colistin,” in particular, for MIC measurement and for microbiological assays and pharmacokinetic and pharmacodynamic studies.

scholarly journals ENZYME KINETICS IN A HISTOCHEMICAL SYSTEM

1958 ◽  
Vol 6 (6) ◽  
pp. 431-434 ◽  
Author(s):  
EARL P. BENDITT ◽  
MARGARET ARASE
Keyword(s):  
Chemical Kinetics ◽  
Enzyme System ◽  
The Other ◽  
End Point ◽  
Straight Line ◽  
Spontaneous Hydrolysis ◽  
Fixed Quantity ◽  
Set Up ◽  
Kinetics Of ◽  
Hydrolysis Of

Modification of the Lineweaver and Burk method of handling the chemical kinetics of an enzyme system has been made to suit the histochemical conditions. Thus if the reaction is allowed to run to some fixed quantity of end point 1/v becomes proportion to the time necessary to reach this end point. In practice serial dilutions of substrate and serial increments in time of incubation are set up. Slides are then separated under the microscope into groups of equal intensity. A plot of 1/[S] v.s. t fits a straight line as expected. Competition between two substrates, one chromogenic the other non-chromogenic, can be demonstrated. One source of deviation from the theoretical due to spontaneous hydrolysis of substrate has been recognized and can be accounted for.

Influence of medium on alkaline hydrolysis of succinic acid monomethyl and monopropyl esters

1980 ◽  
Vol 45 (11) ◽  
pp. 2873-2882
Author(s):  
Vladislav Holba ◽  
Ján Benko
Keyword(s):  
Succinic Acid ◽  
Kinetic Parameters ◽  
Alkaline Hydrolysis ◽  
Specific Interactions ◽  
Nonaqueous Media ◽  
The Media ◽  
Kinetics Of ◽  
Hydrolysis Of

The kinetics of alkaline hydrolysis of succinic acid monomethyl and monopropyl esters were studied in mixed aqueous-nonaqueous media at various temperatures and ionic strengths. The results of measurements are discussed in terms of electrostatic and specific interactions between the reactants and other components of the reaction mixture. The kinetic parameters in the media under study are related to the influence of the cosolvent on the solvation sphere of the reactants.

Belousov–Zhabotinskii type oscillation reaction with glycerol and kinetics of reactions between the system components

1987 ◽  
Vol 52 (10) ◽  
pp. 2375-2382 ◽  
Author(s):  
Ľubica Adamčíková ◽  
Peter Ševčík
Keyword(s):  
Oscillation System ◽  
Chemical Oscillations ◽  
Oscillation Reaction ◽  
Reaction Solution ◽  
System Components ◽  
Probable Source ◽  
Belousov Zhabotinskii Reaction ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Type Oscillation

Glycerol causes chemical oscillations in Belousov-Zhabotinskii reaction in a closed system as well as in a reaction solution bubbled with nitrogen. Since the oxidation of glycerol with bromate ions does not proceed autocatalytically and bromine in the oxidation state 0 or +1 in the absence of light does not react with glycerol, hydrolysis of bromine is the probable source of bromide ions in the studied oscillation system.

Kinetics of hydrolysis of peroxodisulphate ions in acidic medium to peroxomonosulphuric acid

1981 ◽  
Vol 46 (5) ◽  
pp. 1229-1236 ◽  
Author(s):  
Jan Balej ◽  
Milada Thumová
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Acidic Medium ◽  
Measured Data ◽  
Molar Ratios ◽  
Starting Solution ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of

The rate of hydrolysis of S2O82- ions in acidic medium to peroxomonosulphuric acid was measured at 20 and 30 °C. The composition of the starting solution corresponded to the anolyte flowing out from an electrolyser for production of this acid or its ammonium salt at various degrees of conversion and starting molar ratios of sulphuric acid to ammonium sulphate. The measured data served to calculate the rate constants at both temperatures on the basis of the earlier proposed mechanism of the hydrolysis, and their dependence on the ionic strength was studied.

Cyclization and acid-catalyzed hydrolysis of O-benzoylbenzamidoximes

1986 ◽  
Vol 51 (12) ◽  
pp. 2786-2797
Author(s):  
František Grambal ◽  
Jan Lasovský
Keyword(s):  
Reaction Rate ◽  
Kinetic Isotope ◽  
Acid Base Equilibrium ◽  
Mineral Acids ◽  
Kinetics Of Formation ◽  
Acid Catalyzed ◽  
Ph Scale ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Derivatives Of

Kinetics of formation of 1,2,4-oxadiazoles from 24 substitution derivatives of O-benzoylbenzamidoxime have been studied in sulphuric acid and aqueous ethanol media. It has been found that this medium requires introduction of the Hammett H0 function instead of the pH scale beginning as low as from 0.1% solutions of mineral acids. Effects of the acid concentration, ionic strength, and temperature on the reaction rate and on the kinetic isotope effect have been followed. From these dependences and from polar effects of substituents it was concluded that along with the cyclization to 1,2,4-oxadiazoles there proceeds hydrolysis to benzamidoxime and benzoic acid. The reaction is thermodynamically controlled by the acid-base equilibrium of the O-benzylated benzamidoximes.

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