Fig. 4.

Summary of the secondary deuterium KIEs on the enzymatic and nonenzymatic cyclization of 4. (A) Examples of enrichment plots from experimental trials for the C4D and C12D KIEs for both the nonenzymatic and enzymatic reactions. Black circles denote the observed enrichments (D/H, heavy over light) in the isolated residual substrate. Fitted lines (red/blue) are drawn using the median values of the posterior marginal probability distributions for the initial enrichment and KIE corresponding to the experimental trials shown (Materials and Methods). (B) Overall site-specific KIEs for the nonenzymatic reaction. Values are reported as the median (50th percentile) of the simulated posterior marginal probability distribution for each KIE along with the 68% highest posterior density interval (equivalent to ±1 SD about the median of a Gaussian distribution). Isotope effects computed from the gas-phase model system (13) at 300 K are shown in parentheses. (C) Site-specific KIEs for the SpnF-catalyzed cyclization with values reported as in B. The full simulated posterior marginal probability distributions of each KIE as well as all enrichment plots are shown in SI Appendix, Figs. S3 and S4.