An entropic intermediate is defined as a free energy minimum that is not a potential energy minimum; the favorable entropy in this region of the potential surface is responsible for the increased lifetime of this species. Enabled by <i>ab initio</i> molecular dynamics simulations, entropic intermediates have been identified for several types of reactions. The investigation of entropic intermediate in solvent and in enzyme presents a challenge in computational chemistry. Here, I will talk about our development of a QM/MM method, environment-perturbed transition state sampling, which allows the computation of energetics and dynamics for reactions in condensed media. I will also talk about the application of this method in the investigation of entropic intermediate in the Cope rearrangement that interconnects the [4+2] and [6+4] adduct formed by ambimodal TS in the biosynthesis of SpnF-catalyzed Diels-Alder reactions. Our study further elucidates the fundamental dynamic complexity involved in the biosynthetic reactions catalyzed by enzyme SpnF; the enzyme that was demonstrated as the first stand-alone DAase by Liu and coworkers in 2011. <br/>

Time-resolved mechanism of enzyme SpnF-catalyzed Cope rearrangement: Timing of bond formation and entropic intermediate

2019 Spring National Meeting

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