Negative Ion Electron Capture Dissociation (niECD)
[M – nH]n- + e–(2.5-7.5 eV) → [M – nH](n+1)-• → fragments
niECD was discovered in the Håkansson laboratory (J. Am. Chem. Soc., 2011, 133, 16790). This MS/MS activation method is unique in that a charge-increased rather than charge-decreased intermediate is generated. Because signal is proportional to charge in FTMS, significant fragmentation efficiency improvement is feasible. Also, niECD provides predictable peptide fragmentation in negative ion mode in which many important acidic peptide modifications, including phosphorylation, sulfation, and glycosylation, show improved ionization efficiency.
We are currently funded by the National Science Foundation to continue investigating our proposed niECD zwitterion mechanism by utilizing anionic fixed-charge tags, ion mobility (IM), and computational analysis, to further optimize niECD, including charge state manipulation, combination with vibrational activation, and oil segmented flow for compatibility with liquid chromatography, and to explore the niECD applicability for cross-linked proteins, intact proteins, and nucleic acid complexes.