Figure 7.

³²S/³⁴S isotope related shifts in the vibrational spectra of the H_inact state. A) Resonance Raman spectra were measured on 3 mm DdHydAB samples at 80 K using 514 nm excitation. Experimental spectra of H_inact prepared with natural abundance Na₂S (green trace) and ³⁴S‐labelled Na₂S (blue) in the Fe−S region between 330 and 380 cm⁻¹ (see Figure S25 for the full spectrum). The spectra are normalized to modes at 622 cm⁻¹ and 644 cm⁻¹ corresponding to the amino acid side chains phenylalanine and tyrosine, respectively.30 Experimental (B) and QM/MM‐calculated ⁵⁷Fe NRVS data (C) The corresponding spectra of DdHydAB in the H_inact state with ³²S (green) and ³⁴S (blue) ligand are also displayed in the region between 330 and 380 cm⁻¹ (see Figure S24 for the full spectra and a wider view of the Fe−S region). Calculated band positions using the H_inact‐SH QM/MM model with ³²S and ³⁴S bound at open coordination site of Fe_d are presented in Table S12 and shown as Movies S1 and S2.