scholarly journals Properties of methyl acetimidate and its use as a protein-modifying reagent

1981 ◽  
Vol 193 (1) ◽  
pp. 245-249 ◽  
Author(s):  
A J Makoff ◽  
A D B Malcolm
Keyword(s):  
Ionic Strength ◽  
Rate Constants ◽  
Reaction Mechanisms ◽  
Effect Of Ph ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of the imido ester methyl acetimidate and its rate of amidination of denatured aldolase were investigated under different conditions of temperature, pH and ionic strength. Both rate constants increase greatly with temperature, whereas ionic strength has no effect on either. The effect of pH is more complex. Between pH 6.8 and 8.8 the rate of hydrolysis decreases and the rate of amidination increases. These results are discussed in terms of the reaction mechanisms involved.

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.

ÉTUDE DES EFFETS ÉLECTROSTATIQUES SUR LE MÉCANISME D'ACTION CATALYTIQUE DE LA PHOSPHATASE ALCALINE INTESTINALE DE VEAU

1965 ◽  
Vol 43 (8) ◽  
pp. 2222-2235 ◽  
Author(s):  
Michel Lazdunski ◽  
Jacques Brouillard ◽  
Ludovic Ouellet
Keyword(s):  
Dielectric Constant ◽  
Ionic Strength ◽  
Maximum Activity ◽  
Enzyme Molecule ◽  
High Substrate Concentration ◽  
Nitrophenyl Phosphate ◽  
Phosphatase Alcaline ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of ◽  
Activated Complex

The influence of dioxane and ethanol on the rate of hydrolysis of p-nitrophenyl phosphate in the presence of an intestinal alcaline phosphatase can be interpreted as a dielectric constant effect, at high substrate concentration. The dielectric constant effect is a function of the pH of the medium and is maximum around pH 9.4 at 25 °C and pH 9.0 at 15 °C. An interpretation suggesting that the change in diameter of the enzyme molecule becoming an activated complex is minimum at a pH of maximum activity is proposed. The same model can take into account the influence of the ionic strength on the same reaction.

scholarly journals Proteolytic removal of three C-terminal residues of actin alters the monomer-monomer interactions

1993 ◽  
Vol 289 (3) ◽  
pp. 897-902 ◽  
Author(s):  
M Mossakowska ◽  
J Moraczewska ◽  
S Khaitlina ◽  
H Strzelecka-Golaszewska
Keyword(s):  
Electron Microscopy ◽  
Steady State ◽  
Ionic Strength ◽  
Rate Constants ◽  
Initial Rate ◽  
Critical Concentration ◽  
Rate Of Polymerization ◽  
Low Ionic Strength ◽  
Hydrolysis Of

Homogeneous preparations of actin devoid of the three C-terminal residues were obtained by digestion of G-actin with trypsin after blocking proteolysis at other sites by substitution of Mg2+ for the tightly bound Ca2+. Removal of the C-terminal residues resulted in the following: an enhancement of the Mg(2+)-induced hydrolysis of ATP in low-ionic-strength solutions of actin; an increase in the critical concentration for polymerization; a decrease in the initial rate of polymerization; and an enhancement of the steady-state exchange of subunits in the polymer. Electron microscopy indicated an increased fragility of the filaments assembled from truncated actin. The results suggest that removal of the C-terminal residues increases the rate constants for monomer dissociation from the polymer ends and from the oligomeric species.

Mechanistic Information from the Effect of Pressure on the Kinetics of Hydrolysis of Iodopentaaquochromium(III) Ion

1975 ◽  
Vol 53 (24) ◽  
pp. 3697-3701 ◽  
Author(s):  
Milton Cornelius Weekes ◽  
Thomas Wilson Swaddle
Keyword(s):  
Ionic Strength ◽  
Hydrogen Ion ◽  
Ion Concentration ◽  
Hydrogen Ion Concentration ◽  
Kinetics Of Hydrolysis ◽  
Rate Of Hydrolysis ◽  
Kinetics Of ◽  
Hydrolysis Of ◽  
Aqueous Hclo ◽  
Conjugate Base

The rate of hydrolysis of iodopentaaquochromium(III) ion has been measured as a function of pressure (0.1 to 250 MPa) and hydrogen ion concentration (0.1 to 1.0 mol kg−1) at 298.2 K and ionic strength 1.0 mol kg−1 (aqueous HClO4–LiClO4). The volumes of activation for the acid independent and inversely acid dependent hydrolysis pathways are −5.4 ± 0.5 and −1.6 ± 0.3 cm3 mol−1 respectively, and are not detectably pressure-dependent. Consideration of these values, together with the molar volume change of −3.3 ± 0.3 cm3 mol−1 determined dilatometrically for the completed hydrolysis reaction, indicates that the mechanisms of the two pathways are associative interchange (Ia) and dissociative conjugate base (Dcb) respectively.

The Hydrolysis of Bis(2-chloroethyl) Sulfide (Sulfur Mustard) in Aqueous Mixtures of Ethanol, Acetone and Dimethyl Sulfoxide

1993 ◽  
Vol 46 (3) ◽  
pp. 293 ◽  
Author(s):  
RI Tilley
Keyword(s):  
Transition State ◽  
Dimethyl Sulfoxide ◽  
Rate Constants ◽  
Charge Separation ◽  
Sulfur Mustard ◽  
Transition States ◽  
Aqueous Mixtures ◽  
Sulfide Sulfur ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of bis (2-chloroethyl) sulfide (sulfur mustard) in aqueous mixtures of ethanol, acetone and dimethyl sulfoxide has been measured and compared with previously reported values. Rate constants in water at 25°C for the two consecutive hydrolysis reactions undergone by sulfur mustard were estimated to be (2.93�0.15)×10-3 and (3.87�0.14)×10-3 s-1. Charge separation of 0.42 in the transition states was indicated together with significant solvation of the positive end of the transition state dipoles.

Phosphato complexes of cobalt(III). III. Hydrolysis reactions in perchloric acid media

1968 ◽  
Vol 21 (1) ◽  
pp. 67 ◽  
Author(s):  
SF Lincoln ◽  
DR Stranks
Keyword(s):  
Perchloric Acid ◽  
Rate Constants ◽  
Intramolecular Hydrogen Bonding ◽  
Acid Media ◽  
Water Solvent ◽  
Rate Of Hydrolysis ◽  
Intramolecular Hydrogen ◽  
Hydrolysis Of ◽  
Protonated Complexes ◽  
Rate Behaviour

Rates of hydrolysis of phosphato complexes of oobalt(111) in perchloric acid media ranging from 10-3 to 11.4M have been measured by the rates of release of phosphate from 32P-labelled phosphato complexes. First-order rate behaviour is exhibited under all conditions and half-times range from hours to minutes within the range 45-70�. Bidentate phosphato complexes exhibit the same rates of hydrolysis as the corresponding monodentate complexes due to a rapid conversion of the bidentate into the monodentate form. Rate constants have been measured for three distinct protonated complexes (PI, P2, P3). At 60� these rate constants, expressed in the order of aquo-tetraammine, -penhammine, and ?bisethylenediamine complexes, are PI: 74.0, 1.20, 5.5 X 10-3 min-1; P2: 2.5, 1.20, 0.40 x 10-3 min-1; P3: 20.0, 9.0, 5.5 x 10-3 min-1. A tetraprotonated complex (P4) is incompletely generated even in 11.4M HClO4 where observed rate constants at 60� are 8.2, 3.4, 7.0 x 10-2 min-1 respectively. Intramolecular hydrogen bonding is considered important in the P1 and P2 species, especially in the cis-aquophosphato complexes. The rate of hydrolysis of P3 complexes is linearly dependent on the activity of the water solvent consistent with a mechanism involving SN2 attack of water at a cobalt(111) centre. The P4 complex is considered to hydrolyse via an SNICA mechanism.

EFFECT OF pH, CALCIUM CONCENTRATION AND TEMPERATURE ON THE HYDROLYSIS OF DICALCIUM PHOSPHATE DIHYDRATE

1989 ◽  
Vol 69 (3) ◽  
pp. 689-693 ◽  
Author(s):  
G. W. MORDEN ◽  
G. J. RACZ
Keyword(s):  
Key Words ◽  
Calcium Concentration ◽  
Dicalcium Phosphate ◽  
Dicalcium Phosphate Dihydrate ◽  
Effect Of Ph ◽  
Ph Values ◽  
Phosphate Dihydrate ◽  
Rate Of Hydrolysis ◽  
Hydrolysis Of

The rate of hydrolysis of DCPD to OCP in solutions of different pH values, calcium concentrations and temperatures was studied. Rates of hydrolysis were very slow at pH 6.0, relatively rapid and similar at pH 7.0 and 8.0, much slower at 10 °C than at 20 or 30 °C, and only slightly increased by increasing calcium concentration. Key words: Dicalcium phosphate dihydrate, hydrolysis, pH, temperature, calcium concentration

Kinetics of Total Enzymatic Hydrolysis of Acetylcholine and Acetylthiocholine

2006 ◽  
Vol 61 (3-4) ◽  
pp. 289-294 ◽  
Author(s):  
Pavla Zdražilová ◽  
Šárka Štěpánkova ◽  
Martina Vránova ◽  
Karel Komers ◽  
Alena Komersová ◽  
...  
Keyword(s):  
Ionic Strength ◽  
Enzymatic Hydrolysis ◽  
Rate Constants ◽  
Analytical Methods ◽  
Batch Reactor ◽  
Reaction Scheme ◽  
Second Step ◽  
Kinetics Of ◽  
Hydrolysis Of

Kinetics and the mechanism of total in vitro hydrolyses (i.e. up to the exhaustion of substrate) of acetylcholine and acetylthiocholine by acetylcholinesterase and butyrylcholinesterase were studied in vitro in a batch reactor at 25 °C, pH 8 and ionic strength of 0.11 ᴍ. Every hydrolysis was monitored by 2 - 3 independent analytical methods. All studied types of enzymatic hydrolyses fulfilled the Michaelis - Menten reaction scheme with the irreversible second step. A table of obtained average values of rate constants and estimations of initial molar enzyme concentrations, and discussion of the results are presented.

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