Fig. 1.

Modified linear ion trap-Orbitrap hybrid MS system for performing AI-NETD. (A) NETD, which involves oxidation of precursor peptide anions by a reagent cation, can now be performed in the mass-analyzing quadrupole linear ion trap (A-QLT) and multipurpose dissociation cell (MDC). (B) Modifying the MDC to perform NETD opens access to AI-NETD, in which anionic peptide precursors are concurrently irradiated with IR photons during the ion–ion reaction. This additional photoactivation disrupts peptide secondary gas-phase structure, increasing the efficiency of the NETD reaction. (C) Instrument schematic of the hybrid linear ion trap-Orbitrap mass spectrometer is modified with the MDC in place of the traditional HCD collision cell, in addition to an excavated beam path, ZnSe window, and affixed 10.6 μm CO₂ laser for concentric irradiation of the MDC.