Fig. 3

MALDI-MS analysis of oxidized oligosaccharide products. Reactions containing 10 mg mL⁻¹ PASC, 3 µM LPMO, 0.1 µM CDH, 1 mM lactose and H₂O₂ (120 µM final concentration added in four batches of 30 µM over 30 min) were analysed under different conditions using MALDI-MS. a Overview of selected parts of the MALDI-MS spectra obtained from samples containing all components (PASC, CDH, lactose, LPMO and H₂O₂) showing various oligosaccharide products. b–d Details of selected product spectra under four conditions: PASC with oxidized LPMO (black line), PASC with oxidized LPMO and H₂O₂ (blue line), PASC with CDH, lactose and LPMO (green line) and PASC with CDH, lactose, LPMO and H₂O₂ (red line). Addition of H₂O₂ led to a notable, relative increase in C4-oxidized products compared to the unoxidized forms of the analysed oligosaccharides. All oligosaccharides and their oxidized products were detected as sodium or potassium adducts. Shown are also the theoretical monoisotopic masses of all analysed reaction products. Peaks with no labels are matrix adducts or other, non-carbohydrate based, background signals