Ultraviolet photodissociation of protonated, fixed charge, and charge-reduced peptides

- The fragmentation behavior of three peptides was evaluated by CAD, HCD, and UVPD.
- Fixed charge sites were appended to the N-terminus or C-terminus.
- Peptides with a quaternary amine tag released trimethylamine and generated a mobile proton.
- UVPD spectra of odd electron peptides were dominated by radical-mediated fragmentation.