4.
Putative choline cleavage pathways catalyzed by the CutC. Energy profiles were computed using QM/MM at the B3LYP-D3/6-31G(d) geometry-optimized level, with single-point energies evaluated using B3LYP-D3, ωB97X-D3, and M06-2X functionals with the def2-TZVP basis set. High-level ab initio DLPNO–CCSD(T)/cc-pVQZ/C single-point QM/MM calculations are used as a reference and to test DFT/MM results. Zero-point energy corrections were computed at the B3LYP-D3/6-31G(d) level and applied to all stationary points. Radical localization along the reaction coordinate was monitored via spin density analysis, depicted as magenta isosurfaces (isovalue = 0.008 electrons Å–3), to track electronic reorganization during bond cleavage. Bond lengths are given in angstrom. See Table S1 for complete relative energy data for all methods.
