Heavy atom isotope effects on enzymatic reactions

1994 ◽  
Vol 321 (1-2) ◽  
pp. 35-44 ◽  
Author(s):  
Piotr Paneth
Keyword(s):  
Isotope Effects ◽  
Heavy Atom ◽  
Enzymatic Reactions

scholarly journals Unusual origins of isotope effects in enzyme-catalysed reactions

2006 ◽  
Vol 361 (1472) ◽  
pp. 1341-1349 ◽  
Author(s):  
Dexter B Northrop
Keyword(s):  
High Pressure ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Zero Point ◽  
Protein Domain ◽  
Enzymatic Reactions ◽  
Volume Changes ◽  
Mass Unit ◽  
Deuterium Isotope Effects ◽  
Domain Motions

High hydrostatic pressure is a neglected tool for probing the origins of isotope effects. In chemical reactions, normal primary deuterium isotope effects (DIEs) arising solely from differences in zero point energies are unaffected by pressure; but some anomalous isotope effects in which hydrogen tunnelling is suspected are partially suppressed. In some enzymatic reactions, high pressure completely suppresses the DIE. We have now measured the effects of high pressure on the parallel 13 C heavy atom isotope effect of yeast alcohol dehydrogenase and found that it is also suppressed by high pressure and, similarly, suppressed in its entirety. Moreover, the volume changes associated with the suppression of both deuterium and heavy atom isotope effects are virtually identical. The equivalent decrease in activation volumes for hydride transfer, when one mass unit is added to the carbon end of a scissile C–H bond as when one mass unit is added to the hydrogen end, suggests a common origin. Given that carbon is highly unlikely to undergo tunnelling, it follows that hydrogen is not doing so either. The origin of these isotope effects must lie elsewhere. We offer protein domain motions as a possibility.

Theoretical Simulations of Heavy-Atom Kinetic Isotope Effects in Aliphatic Claisen Rearrangement

2020 ◽  
Vol 124 (51) ◽  
pp. 10678-10686
Author(s):  
Yuqing Xu ◽  
Kin-Yiu Wong ◽  
Meishan Wang ◽  
Desheng Liu ◽  
Wenkai Zhao ◽  
...  
Keyword(s):  
Claisen Rearrangement ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Kinetic Isotope Effects ◽  
Kinetic Isotope ◽  
Theoretical Simulations

The influence of charge on nuclear magnetic resonance isotope effects

1987 ◽  
Vol 65 (12) ◽  
pp. 2707-2712 ◽  
Author(s):  
Roderick E. Wasylishen ◽  
Neil Burford
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Isotope Effects ◽  
Heavy Atom ◽  
Coupling Constants ◽  
Molecular Orbital Calculations ◽  
Isoelectronic Series ◽  
Deuterium Isotope Effects ◽  
Charged Ions ◽  
Nuclear Magnetic

Deuterium isotope effects on the 31P shielding constants and spin–spin coupling constants in the isoelectronic series, PH2−, PH3, PH4+, are examined. Also, deuterium isotope effects on the nuclear magnetic resonance parameters of SnH3− are examined and compared with our earlier results on SnH4 and SnH3+. The experimental results are analyzed using the models of Jameson and Osten. In each isoelectronic series it is found that the isotope effects on the heavy atom chemical shifts are largest for the negatively charged ions and essentially zero for the positively charged ions, as predicted by recent molecular orbital calculations. The primary isotope effects on J(A,H) are positive for all species containing lone-pair electrons, otherwise Δp1J(A,H) is negative. The primary and secondary isotope effects on J(Sn,H) in the SnH3− ion are the largest reported to date.

Sign in / Sign up

Export Citation Format

Share Document