Figure 3.

In crystallo Raman spectroscopic and QM/MM validation of MUA peroxidation. a) Raman spectra of apo-UOX (grey), anaerobic UOX:MUA (green), UOX:5-PMUA (brown), and UOX:^H5-PMUA crystals (orange). ^H5-PMUA (H for heavy) refers to MUA reacted with ¹⁸O₂. b) Close-up of the 500–700 cm⁻¹ spectral region. c) QM/MM Raman spectrum in the 570–620 cm⁻¹ region for MUA dianion (green), 5-PMUA monoanion (brown), and ^H5-PMUA monoanion (orange) at the MP2/6-31+G* level of theory. A band at 600 cm⁻¹ (experimental 605 cm⁻¹) is predicted for 5-PMUA. It is downshifted by −9 cm⁻¹ (experimental −9 cm⁻¹) in the presence of ¹⁸O peroxide oxygen atoms. A band at 597 cm⁻¹ (experimental 597 cm⁻¹) of lower intensity compared to the “peroxide signature band” is predicted for MUA.