Fig. 1

Cleavage of Aβ1–42 by matriptase. a Synthetic human Aβ42 (1 µg, Bio-Techne) was mixed with a recombinant human matriptase protease domain (MatPD, “+” = 0.1 µg, “+++” = 0.3 µg, Bio-Techne) in a total volume of 20 µl with reaction buffer. Samples containing Aβ42 or MatPD alone were also prepared. The reactions were carried out at 37 °C for either overnight or 1.5 h, as indicated, before the samples were analyzed by SDS-PAGE and stained with Coomassie Brilliant Blue. b Duplicate samples as described for lanes 1 and 3 were sent for MALDI-TOF MS analysis, performed by the University of Florida Proteomics & Mass Spectrometry Core on a 4700 Proteomics Analyzer (Applied Biosystems). Peptide fragments generated by MatPD from Aβ42 were identified in the data graph from Sample 3 (Aβ42 + MatPD), as shown by the red boxes with the calculated (average) and observed masses listed in the table. Insets: left—separation of peaks “L17-K28” and “H6-K16” by MSight [21]; right—spectrum from Sample 1 (Aβ42 alone) set to the same intensity scale and in the same mass range. Other boxed peaks were also examined by MSight over the corresponding mass spectrum ranges between Samples 3 and 1 (not shown)