Figure 1. Stc2-catalysis using a [Ru(bpy)₃]²⁺-ascorbate pair as a photo-reduction system.

a), Scheme of Stc2-catalyzed N-demethylation reaction with [Ru(bpy)₃]²⁺ as the photo-sensitizer (PS). b), Stc2 reduction time-course monitored by UV-visible spectroscopy. The control used is the [Ru(bpy)₃]²⁺ solution. c), EPR spectrum of reduced Stc2, which contains two species, A and B (red traces). Experimental data (in blue) are overlaid with simulation (black trace). The insert is the full EPR spectrum, showing no other species. d), EPR spectrum of NO treated reduced Stc2. The features near g = 4 correspond to {S = 3/2}⁷ species, with E/D = 0.015. The signal at g = 2.04 is DNIC, and the g = 1.92 and 1.75 signals are from [2Fe-2S]⁺. e), ¹H-NMR spectra of Stc2-catalyzed stachydrine N-demethylation reaction [N-methyl group signals of the substrate (1) and product (2) in ¹H-NMR spectrum], under single turnover condition (trace i); under dark (trace ii); in the absence of Stc2 (trace iii); and under multiple turnover conditions (trace iv) using [Ru(bpy)₃]²⁺ as the photo-sensitizer and ascorbate as the sacrficial reagent.