Revealing Catalytically Relevant Surface Species by Kinetic Isotope Effect Spectroscopy: H-Bonding to Ester Carbonyl of trans-Ethyl Pyruvate Controls Enantioselectivity on a Cinchona-Modified Pt Catalyst

2018 ◽  
Vol 9 (5) ◽  
pp. 996-1001 ◽  
Author(s):  
Fabian Meemken ◽  
Laura Rodríguez-García
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Ethyl Pyruvate ◽  
Pt Catalyst ◽  
Surface Species ◽  
Ester Carbonyl ◽  
Kinetic Isotope

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.

Isotope effect profiles in the N-demethylation of N,N-dimethylanilines: a key to determine the pKa of nonheme Fe(iii)–OH complexes

2015 ◽  
Vol 51 (24) ◽  
pp. 5032-5035 ◽  
Author(s):  
Alessia Barbieri ◽  
Martina De Gennaro ◽  
Stefano Di Stefano ◽  
Osvaldo Lanzalunga ◽  
Andrea Lapi ◽  
...  
Keyword(s):  
Isotope Effect ◽  
Kinetic Isotope Effect ◽  
Kinetic Isotope

pKa of [(N4Py)FeIII–OH]2+ is obtained from the kinetic isotope effect profiles in the N-demethylation of N,N-dimethylanilines promoted by [(N4Py)FeIVO]2+.

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