Investigation of the mechanism of electron capture and electron transfer dissociation of peptides with a covalently attached free radical hydrogen atom scavenger

- TEMPO radical has high hydrogen affinity (∼280 kJ/mol) and low electron affinity (∼0.45 eV).
- In ExD, H-atom scavenging by TEMPO radical interrupts NCα bond cleavage.
- Long-lived intermediates in ExD are implicated to accommodate H-atom scavenging.