Proteolytic digests of fibrinogen αC (233-425) show three reactive glutamines in a MALDI-TOF mass spectrometry. (A) αC (233-425) sequence showing position of reactive glutamine in bold; (B) MALDI-TOF mass spectrometry spectrum of αC (233-425) digested with chymotrypsin contained a fragment with one reactive glutamine Q328 at 2448.7 m/z. (C) GluC digest of αC (233-425) showed two peaks (1550.5 m/z and 1349.3 m/z) containing Q366 and Q237, respectively, in the MALDI-TOF mass spectrometry.