Experimental Evidence for Hydrogen Tunneling when the Isotopic Arrhenius Prefactor (AH/AD) is Unity
- 5 December 2008
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 130 (52) , 17632-17633
- https://doi.org/10.1021/ja806354w
Abstract
The temperature dependence of the kinetic isotope effect (KIE) is one of the major tools used for the investigation of hydrogen tunneling in condensed phase. Hydrogen transfer reactions displaying isotopic Arrhenius prefactor ratios (AH/AD) of unity are generally ascribed to a semiclassical mechanism. Here, we have identified a double mutant of soybean lipoxygenase (SLO-1, an enzyme previously shown to follow quantum mechanical hydrogen tunneling), that displays an AH/AD of unity and highly elevated (nonclassical) KIEs. This observation highlights the shortcoming of assigning a hydrogen transfer reaction to a semiclassical model based solely on an Arrhenius prefactor ratioKeywords
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