Models for tunneling in enzyme reactions

The detailed description of the models currently being used to describe tunneling in enzyme-catalyzed reactions will be undertaken in a later part of our treatment in which theoretical studies will be reviewed and ideas about the role of protein motions will be a focus. At this point, we will briefly sketch the most commonly used ideas. 

Currently suggested models for tunneling increasingly invoke protein dynamics . These models envision either a series of conformational fluctuations that lead to a suitable tunneling configuration ( passive dynamics ) or a more active role for the enzyme motions ( active dynamics or gating ).64 On the model of 

Because both the passive fluctuations and the modulating vibrations can require thermal excitation, this model is capable of accounting for temperature-dependent isotope effects, including those traditionally described by the Bell model. Theoretical studies, which will be the topic of the second and third parts of this three-part series of articles, have not yet produced a consensus on the contribution of specific protein motions to enzyme catalysis. 

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Observations that do not definitively indicate tunneling 70 Observations that likely indicate tunneling 71 Models for tunneling in enzyme reactions 72 Bell tunneling 72... 

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