Figure 2.

Illustration of PIR fragmentation and data acquisition using in-source collision induced dissociation (ISCID). Use of ISCID is alternated between each spectrum acquisition, generating mass spectra with either intact PIR precursor ions, or fragmented PIR product ions. Inter-cross-linked relationships are made from the summation two peptide ion masses and the reporter ion mass in the product ion scans to produce the intact precursor ion mass observed in the previous scan event.