Initial rate constants for coagulation in the presence of energy minima of restricted depth

1975 ◽  
Vol 71 ◽  
pp. 468 ◽  
Author(s):  
Peter Richmond ◽  
Alec L. Smith
Keyword(s):  
Rate Constants ◽  
Initial Rate

KINETIC STUDIES OF METHYL-BIS-β-CHLOROETHYLAMINE: III. THE KINETICS OF THE DIMERIZATION IN METHANOL

1948 ◽  
Vol 26b (2) ◽  
pp. 175-180 ◽  
Author(s):  
C. A. Winkler ◽  
A. W. Hay ◽  
A. L. Thompson
Keyword(s):  
Rate Constants ◽  
Initial Rate ◽  
Kinetic Studies ◽  
First Order ◽  
Rate Expression ◽  
Principal Reaction ◽  
Kinetics Of ◽  
Rate Controlling Step

The principal reaction of methyl-bis-β-chloroethylamine in methanol is dimerization, which results in one chlorine from each molecule becoming ionic, but this is accompanied by slight alcoholysis. The rate-controlling step is believed to be the first order formation of an ethylenimonium ion which reacts rapidly with one of its kind to form dimer. The rate expression as calculated from initial rate constants is k (initial) = 4.0 × 1013e−19600/RThr.−1.

scholarly journals The significance of abrupt transitions in Lineweaver–Burk plots with particular reference to glutamate dehydrogenase. Negative and positive co-operativity in catalytic rate constants

1973 ◽  
Vol 131 (1) ◽  
pp. 97-105 ◽  
Author(s):  
Paul C. Engel ◽  
William Ferdinand
Keyword(s):  
Glutamate Dehydrogenase ◽  
Rate Equation ◽  
Rate Constants ◽  
Initial Rate ◽  
Current Knowledge ◽  
The Other ◽  
Catalytic Rate Constant ◽  
Catalytic Rate ◽  
Linear Sections ◽  
Glucose 6 Phosphate Dehydrogenase

1. Lineweaver–Burk plots for glutamate dehydrogenase, glucose 6-phosphate dehydrogenase and several other enzymes show one or more abrupt transitions between apparently linear sections. These transitions correspond to abrupt increases in the apparent Km and Vmax. with increasing concentration of the varied substrate. 2. The generalized reciprocal initial-rate equation for a multi-site enzyme requires several restrictions to be put on it in order to generate such plots. These mathematical conditions are explored. 3. It is shown that the effective omission of a term in the denominator of the reciprocal initial-rate equation represents a minimal requirement for generation of abrupt transitions. This corresponds in physical terms to negative co-operativity followed by positive co-operativity affecting the catalytic rate constant for the reaction. 4. Previous models for glutamate dehydrogenase cannot adequately account for the results. On the other hand, the model based on both negative and positive co-operativity gives a good fit to the experimental points. 5. The conclusions are discussed in relation to current knowledge of the structure and mechanism of glutamate dehydrogenase.

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.

Metal Complexes as Antioxidants. I. The Reaction of Zinc Dialkyldithiophosphates and Related Compounds with Peroxy Radicals

1973 ◽  
Vol 51 (10) ◽  
pp. 1543-1553 ◽  
Author(s):  
J. A. Howard ◽  
Y. Ohkatsu ◽  
J. H. B. Chenier ◽  
K. U. Ingold
Keyword(s):  
Electron Transfer ◽  
Metal Complexes ◽  
Rate Constants ◽  
Initial Rate ◽  
Peroxy Radicals ◽  
Zinc Dialkyldithiophosphates ◽  
Zinc Diethyldithiocarbamate ◽  
Inhibition Studies ◽  
Kinetics Of ◽  
Related Compounds

The kinetics of the inhibition of the autoxidation of several hydrocarbons by a number of zinc dialkyldithiophosphates and by zinc isopropylxanthate and zinc diethyldithiocarbamate have been studied at 30c and at 50c. The oxidations were generally auto-retarding but initial rate measurements showed that these compounds trapped peroxy radicals and allowed rate constants for this process to be calculated. Rate constants for the reaction of t-butylperoxy radicals with these compounds have been measured by a kinetic e.p.r. method in the temperature range 0c to −90c. Extrapolation of the e.p.r. data to the temperatures of the inhibition studies showed that the various experimental procedures yielded results in satisfactory agreement with one another.It is suggested that the reaction of peroxy radicals with zinc complexes involves reaction at the metal center either by an electron transfer or an SH2 process.

scholarly journals The kinetics of oxidation of ferroperoxidase by molecular oxygen. A model of a terminal oxidase

1974 ◽  
Vol 141 (1) ◽  
pp. 265-272 ◽  
Author(s):  
Charles F. Phelps ◽  
Eraldo Antonini ◽  
Giorgio Giacometti ◽  
Maurizio Brunori
Keyword(s):  
Computer Simulation ◽  
Rate Constants ◽  
Time Course ◽  
Initial Rate ◽  
Time Range ◽  
Analogue Computer ◽  
Terminal Oxidase ◽  
Kinetics Of Oxidation ◽  
Rate Limiting ◽  
Kinetics Of

1. The decay of oxyferroperoxidase to ferriperoxidase was studied by rapidly mixing solutions of ferroperoxidase with various amounts of oxygen and following the time-course of appearance of oxyferroperoxidase and its subsequent decay to ferriperoxidase by reaction with ferroperoxidase. 2. The scheme can be accommodated by and [Formula: see text] and occurs without detectable intermediates being observed in the millisecond time-range. 3. Analogue-computer simulation of the reaction is in agreement with the initial rate-limiting reaction being an intermolecular, not intramolecular, electron-donating process, and analysis of the data leads to quantitative values for the rate constants of the overall process. 4. The reaction of oxyferroperoxidase with ferroperoxidase is a model of a terminal oxidase, and the results are discussed in terms of the possible importance of this reaction in peroxidase function, and also in the light it throws on autoxidation of haem compounds.

The kinetics of the reactions of sheep haemoglobin with iso cyanides

1960 ◽  
Vol 152 (948) ◽  
pp. 331-345 ◽  
Keyword(s):  
Chain Length ◽  
Steric Hindrance ◽  
Rate Constants ◽  
Homologous Series ◽  
Experimental Error ◽  
Initial Rate ◽  
The Other ◽  
Tertiary Butyl ◽  
Kinetics Of ◽  
Haemoglobin Molecule

The kinetic basis for the decrease in affinity of haemoglobin and myoglobin for successive members of the series of alkyl iso cyanides has been investigated. The initial rate of combination of ethyl, n -propyl, iso propyl, iso butyl and tertiary butyl iso cyanides with haemoglobin and with myoglobin decreases with increasing chain-length by about 500-fold in the case of haemoglobin and about 40-fold in the case of myoglobin. The rate of combination of the fourth iso cyanide molecule with haemoglobin (i. e. I + Hb 4 I 3 → Hb 4 I 4 ) is, however, only about 14 times smaller for tertiary butyl as compared with ethyl iso­ cyanide; this finding is in line with Pauling’s suggestion that combination of successive ligand molecules with haemoglobin decreases the steric hindrance for combination with further ligand molecules. The latter effect, however, varies considerably from ligand to ligand and is not only a property of the haemoglobin molecule. The velocity of dissociation of the first molecule of iso cyanide from saturated haemoglobin, on the other hand, is the same within experimental error for all members of the series. With myoglobin the rate constants for dissociation show differences of two- to three-fold, but there is no systematic trend. Thus the burden of accounting for the differences in affinity between the iso cyanides falls upon the combination velocity constants. This finding is in contrast to that for the gaseous ligands O 2 , CO and NO, where the affinity is primarily determined by the dissociation velocity constants. The bearing of the results on the ‘crevice’ hypothesis of haemoglobin structure is discussed. In line with the well-known fact that the first member of an homologous series is often anomalous it was found that the rate of dissociation of methyl iso cyanide from haemoglobin was about 50 times greater than that for all the higher homologues of the series. Preliminary experiments were carried out on the rate of combination of free haem with several of the iso cyanides, but were not pursued further on account of the difficulties mentioned in the text.

Comparing the DBT Conversion by Using Crystalline WS2 and WS2 Electron Irradiated Catalyst

1998 ◽  
Vol 549 ◽  
Author(s):  
R. Rangel ◽  
G. Alonso ◽  
E. Adem ◽  
S. Fuentes ◽  
D. H. Galvan
Keyword(s):  
Catalytic Activity ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Area ◽  
Rate Constants ◽  
Initial Rate ◽  
Microstructural Changes ◽  
X Ray ◽  
Sem Micrographs ◽  
Scanning Electron

AbstractA catalytic study has been performed in WS2 irradiated with electrons at 1000 kGy. The purpose is to compare irradiated WS2 with WS2 crystalline in terms of DBT conversion, selectivity and surface area analysis. Also, Scanning Electron Microscope (SEM), X-raydiffraction were performed to show microstructural changes induced by irradiation. We found that DBT conversion increased by 55 % if compared with WS2 crystalline. The surface area decreased and the initial rate constants increased by a factor of four times. The selectivity for DCH after irradiation has decreased, while the selectivity for DIF and PCH has increased substantially. The DYH/DHS ratio has decreased in 42 %. The SEM micrographs showed that irradiation, at this level, produced certain damage in the crystallinity. The X-ray analysis showed different distribution in the intensity of the principal peaks after irradiation was achieved. This behavior could be correlated to the surface area decrement and the enhancing of the catalytic activity in WS2.

Hydrogenation of Fatty Acid Esters. III. Hydrogenation of Methyl (9Z,12Z)-Octadecadienoate and Methyl (9Z,12Z,15Z)-Octadecatrienoate

1992 ◽  
Vol 57 (12) ◽  
pp. 2593-2604 ◽  
Author(s):  
Jana Krupičková ◽  
Jaroslav Včelák ◽  
Jiří Hetflejš
Keyword(s):  
Fatty Acid ◽  
Rate Constants ◽  
Initial Rate ◽  
Product Distribution ◽  
Fatty Acid Esters ◽  
Product Analysis ◽  
First Order ◽  
Time Changes ◽  
Acid Esters

The title hydrogenation catalyzed by nickel(II) 2,4-pentanedionate-triethylaluminium system has been studied with the use of combination of initial rate measurements with time changes of product distribution. It was found that the hydrogenation of methyl (9Z,12Z)-octadecadienoate is first order in the octadecadienoate. Similar results were obtained also for (9Z,12Z,15Z)-octadecatrienoate. The course of both reactions has been described by models involving set of parallel and consecutive hydrogenation steps and reversible isomerizations. Computed rate constants for hydrogenation of methyl (9Z,12Z)-octadecadienoate support qualitative conclusions deduced from the product analysis.

scholarly journals The kinetics of substrate-induced inactivation

1991 ◽  
Vol 279 (1) ◽  
pp. 87-94 ◽  
Author(s):  
S G Waley
Keyword(s):  
Rate Constant ◽  
Rate Constants ◽  
Initial Rate ◽  
Active Form ◽  
Partition Ratio ◽  
Enzymic Activity ◽  
Progress Curve ◽  
Inactive Form ◽  
Reversible Formation ◽  
Kinetics Of

The kinetics of a branched-pathway mechanism for a simple enzymic reaction were studied. In this mechanism there is reversible formation of an inactive form of the second complex along the pathway. This substrate-induced inactivation typically results in the progress curve showing a burst. Three parameters can be obtained from the progress curve: the initial rate, the final rate and the rate constant characterizing the transient. The rate constant for the conversion of the inactive form of the complex into the active form can be obtained either from these parameters or by measuring the regain of enzymic activity. The partition ratio can also be obtained from the three parameters; this is the ratio of the rate of conversion of complex into product to the rate of conversion of complex into inactive form. Simulations give guidance to the conditions required for accurate determinations of the rate constants.

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