(a) Remaining non-oxidized Aβ28 after successive additions of ascorbate (4 nmol, final conc. 20 μM) or ascorbate/H2O2 (4/10 nmol, final conc. 20/50 μM). Aβ28 25 μM and Cu2+ 20 μM, phosphate buffered pH 7.4 (50 mM). Ordinate: ratio between the peak area of non-oxidized Aβ28 and the reference peak area of non-ox Aβ28 (no addition of ascorbate nor H2O2). HPLC/HRMS, m/z 1087.8503, 816.1397, 653.1133 ([M + nH]n+, n = 3, 4, 5), 5 ppm accuracy. (b) Ascorbate consumption measured at 265 nm as a function of the reaction time; Aβ28 25 μM, Cu2+ 20 μM, phosphate buffered pH 7.4 (50 mM), ascorbate 20 μM, with or without H2O2 50 μM.