Fig. 1.

MALDI-TOF MS CSF Aβ peptide patterns of a a non-symptomatic control, b Patient 1 in the acute phase of BM and c after antibiotic treatment. The recorded isotope patterns of d Aβ 1–20 and e Aβ 1–40 in acute BM are shown in blue bars, and the expected isotope patterns of the peptides without ¹⁸O incorporation and with one oxygen atom exchanged for ¹⁸O at 50% abundance is indicated by red and green bars, respectively