Fig. 6

The XPS spectra showing nitrogen profiles of CvATA and SpATA aminated galactomannan with oxidized and non-oxidized galactomannan as references. The spectra were adjusted by scaling amide peaks to the same height so the amine peaks could be directly compared. The intensity of peaks is shown using a linear scale. Reactions (500 µL) comprised 50 mM potassium phosphate buffer (pH 7.5), 20 µM PLP, 29.8 µg/mL FgrGaOx, 12.8 µg/mL catalase, 1.8 µg/mL HRP, 0.15 mg/mL ATA, 5 mM (S)-1-PEA and 0.29% galactomannan containing 5 mM galactose. Reactions were carried out at 37 °C and 600 rpm for 24 h in 1.5 mL centrifuge tubes. The oxidized reference did not contain ATA, and the non-oxidized reference did not contain any enzymes. Enzymes (SpATA, FgrGaOx, catalase, and HRP) were added to both references after reactions to the concentrations stated above. Samples were desalted immediately using 100 kDa centrifuge filters before freeze–drying and XPS analyses