From Wikipedia: Electron-transfer dissociation (ETD) is a method of fragmenting ions in a mass spectrometer.[1][2] Similar to electron-capture dissociation, ETD induces fragmentation of cations (e.g. peptides or proteins) by transferring electrons to them. It was invented by Donald F. Hunt, Joshua Coon, John E. P. Syka and Jarrod Marto at the University of Virginia.[3]