Kinetic studies on the reaction mechanism of p-hydroxybenzoate hydroxylase

Biochemistry ◽  
1970 ◽  
Vol 9 (16) ◽  
pp. 3235-3242 ◽  
Author(s):  
Satoshi Nakamura ◽  
Yasuyuki Ogura ◽  
Keiji Yano ◽  
Naoki Higashi ◽  
Kei Arima
Keyword(s):  
Reaction Mechanism ◽  
Kinetic Studies ◽  
Hydroxybenzoate Hydroxylase

Ligand-Enabled γ-C(sp3)–H Olefination of Free Carboxylic Acids

2020 ◽  
Author(s):  
Kiron Kumar Ghosh ◽  
Alexander Uttry ◽  
Francesca Ghiringhelli ◽  
Arup Mondal ◽  
Manuel van Gemmeren
Keyword(s):  
Reaction Mechanism ◽  
Carboxylic Acids ◽  
Michael Addition ◽  
Kinetic Studies ◽  
Wide Range ◽  
Palladium Catalyzed

We report the ligand enabled C(sp3)–H activation/olefination of free carboxylic acids in the γ-position. Through an intramolecular Michael-addition, δ-lactones are obtained as products. Two distinct ligand classes are identified that enable the challenging palladium-catalyzed activation of free carboxylic acids in the γ-position. The developed protocol features a wide range of acid substrates and olefin reaction partners and is shown to be applicable on a preparatively useful scale. Insights into the underlying reaction mechanism obtained through kinetic studies are reported.<br>

From the Understanding of the Reaction Mechanism Towards Optimizing the Deposition Rate and Optoelectronic Properties of a-Si:H

1989 ◽  
Vol 149 ◽  
Author(s):  
S. Veprek ◽  
M. Heintze ◽  
R. Bayer ◽  
N. Jurčik-Rajman
Keyword(s):  
Reaction Mechanism ◽  
Surface Coverage ◽  
Kinetic Studies ◽  
Reactive Intermediates ◽  
Sticking Coefficient ◽  
High Quality ◽  
Rate Determining Step ◽  
Homogeneous Good ◽  
Good Agreement

ABSTRACTWe present new results of kinetic studies of the deposition of high quality a-Si:H which strongly support the reaction mechanism suggested in our earlier papers: 1. SiH4 → SiH2; 2. SiH2 + SiS4 → Si2H6 (SiH2 + Si2H6 → Si3H6); 3. Si2H6 → 2a-Si:H (Si3H8 → 3a-Si:H). The “SiH3 mechanism”, as promoted by several workers, is in contradiction with these experimental facts.The di- and trisilane, which have a much higher reactive sticking coefficient than monosilane, play the role of reactive intermediates which facilitate the heterogeneous decomposition of silicon carrying species at the surface of the growing film. The values of the reactive sticking coefficient of Si2H6 and Si3H8 depend on the surface coverage by chemisorbed hydrogen; they increase with decreasing surface coverage. Under the conditions of the growth of high quality a-Si:H films the reactive sticking coefficient of disilane amounts to 10−4 to 10−2 which is in a good agreement with recent data of other authors.The rate determining step of the growth of high quality a-Si:H films is the desorption of hydrogen from the surface of the growing film. This can be strongly enhanced by ion bombardment at impact energy of <100 eV. In this way, homogeneous, good quality films were deposited at rates up to 1800 Angströms/min, and there is a well justified hope that this rate can be further increased.

Kinetic studies of mutant human erythrocyte adenine phosphoribosyltransferases

1968 ◽  
Vol 46 (7) ◽  
pp. 703-706 ◽  
Author(s):  
J. Frank Henderson ◽  
Helen R. Miller ◽  
William N. Kelley ◽  
Frederick M. Rosenbloom ◽  
J. Edwin Seegmiller
Keyword(s):  
Reaction Mechanism ◽  
Human Erythrocyte ◽  
Enzyme Activities ◽  
Kinetic Studies ◽  
Kinetic Constants ◽  
Heat Inactivation ◽  
Adenine Phosphoribosyltransferase ◽  
Michaelis Constants ◽  
Low Degrees ◽  
Reduced Activity

The kinetic constants and reaction mechanism of human erythrocyte adenine phosphoribosyltransferase from individuals whose enzyme activities have high, intermediate, or low degrees of stability to heat inactivation, and in a human mutant with reduced activity of this enzyme, have been measured. The Michaelis constants for one or both substrates are different from normal in seven mutants.

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