Calicheamicin γ1I and phenyl tert-butyl nitrone (PBN): observation of a kinetic isotope effect by an ESR study

2010 ◽  
Vol 46 (5) ◽  
pp. 737-739 ◽  
Author(s):  
Toyonobu Usuki ◽  
Mari Kawai ◽  
Koji Nakanishi ◽  
George A. Ellestad
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Tert Butyl ◽  
Kinetic Isotope

SOME DEUTERIUM KINETIC ISOTOPE EFFECTS: IV. β-DEUTERIUM EFFECTS IN WATER SOLVOLYSIS OF ETHYL, ISOPROPYL, AND tert-BUTYL COMPOUNDS

1960 ◽  
Vol 38 (11) ◽  
pp. 2171-2177 ◽  
Author(s):  
K. T. Leffek ◽  
J. A. Llewellyn ◽  
R. E. Robertson
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Isotope Effects ◽  
Kinetic Isotope Effects ◽  
Alkyl Halides ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Deuterium Isotope Effects ◽  
Intramolecular Forces

The secondary β-deuterium isotope effects have been measured in the water solvolytic reaction of alkyl halides and sulphonates for primary, secondary, and tertiary species. In every case the kinetic isotope effect was greater than unity (kH/kD > 1). This isotope effect may be associated with varying degrees of hyperconjugation or altered non-bonding intramolecular forces. The experiments make it difficult to decide which effect is most important.

Sterically Hindered Aromatic Compounds. VI. A Remote ε-Deuterium Kinetic Isotope Effect in the Solvolysis of Perdeutero-2,4,6-tri-tert-butylbenzyl Chloride

1975 ◽  
Vol 53 (21) ◽  
pp. 3171-3174 ◽  
Author(s):  
L. Ross C. Barclay ◽  
John R. Mercer ◽  
Peter J. MacAulay
Keyword(s):  
Transition State ◽  
Isotope Effect ◽  
Aromatic Compounds ◽  
Kinetic Isotope Effect ◽  
Inductive Effect ◽  
Steric Effects ◽  
Deuterium Isotope Effect ◽  
Tert Butyl ◽  
Kinetic Isotope ◽  
Sterically Hindered

2,4,6-Tri-tert-butylbenzyl chloride deuterated at the three tert-butyl groups was synthesized. Conductimetric solvolysis studies of the normal and perdeutero-2,4,6-tri-tert-butylbenzyl chloride at 30.06 °C in 80% ethanol–water provides evidence for an inverse remote ε-deuterium isotope effect, kH/kD = 0.873−0.874. Under the same conditions the α-deuterium isotope effect was kH/kαD = 1.166 per deuterium, indicative of limiting solvolytic behavior. The remote ε-deuterium isotope effect for the perdeutero compound is discussed in terms of the inductive effect of deuterium and steric effects on the transition state conformation.

Quantum electrocatalysts: theoretical picture, electrochemical kinetic isotope effect analysis, and conjecture to understand microscopic mechanisms

2020 ◽  
Vol 22 (20) ◽  
pp. 11219-11243 ◽  
Author(s):  
Ken Sakaushi
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Effect Analysis ◽  
Kinetic Isotope

The fundamental aspects of quantum electrocatalysts are discussed together with the newly developed electrochemical kinetic isotope effect (EC-KIE) approach.

scholarly journals l-mandelate dehydrogenase from Rhodotorula graminis: comparisons with the l-lactate dehydrogenase (flavocytochrome b2) from Saccharomyces cerevisiae

1993 ◽  
Vol 290 (1) ◽  
pp. 103-107 ◽  
Author(s):  
O Smékal ◽  
M Yasin ◽  
C A Fewson ◽  
G A Reid ◽  
S K Chapman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Lactate Dehydrogenase ◽  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Dimensional Structure ◽  
Striking Difference ◽  
Kinetic Properties ◽  
Proton Abstraction ◽  
Rate Determining Step ◽  
Kinetic Isotope

L-Lactate dehydrogenase (L-LDH) from Saccharomyces cerevisiae and L-mandelate dehydrogenase (L-MDH) from Rhodotorula graminis are both flavocytochromes b2. The kinetic properties of these enzymes have been compared using steady-state kinetic methods. The most striking difference between the two enzymes is found by comparing their substrate specificities. L-LDH and L-MDH have mutually exclusive primary substrates, i.e. the substrate for one enzyme is a potent competitive inhibitor for the other. Molecular-modelling studies on the known three-dimensional structure of S. cerevisiae L-LDH suggest that this enzyme is unable to catalyse the oxidation of L-mandelate because productive binding is impeded by steric interference, particularly between the side chain of Leu-230 and the phenyl ring of mandelate. Another major difference between L-LDH and L-MDH lies in the rate-determining step. For S. cerevisiae L-LDH, the major rate-determining step is proton abstraction at C-2 of lactate, as previously shown by the 2H kinetic-isotope effect. However, in R. graminis L-MDH the kinetic-isotope effect seen with DL-[2-2H]mandelate is only 1.1 +/- 0.1, clearly showing that proton abstraction at C-2 of mandelate is not rate-limiting. The fact that the rate-determining step is different indicates that the transition states in each of these enzymes must also be different.

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