The C-H and S-H distances at proS-TS ES are still quite short at 1.57 and 1.52 Å, while the S-H-C angle is more bent at 145 o (Fig. , Fig. ). Moreover, the radical density is more localized in proS-TS ES compared to proR-TS ES , as the spin densities are 0.36 at the S atom and 0.66 at C of Gly829.