Electron Detachment Dissociation in a hybrid radio frequency Linear Ion Trap/TOF Mass Spectrometer (2008)
Undergraduates: Travis Greene, Jared Bushey Takashi Baba, Gary L. Glish
Faculty Advisor: Garu Glish
Department: Chemistry
Electron Detachment Dissociation in a hybrid radio frequency Linear Ion Trap/Time of Flight Mass Spectrometer
Introduction
Electron detachment dissociation (EDD) provides complimentary product ion information to electron capture dissociation (ECD). While ECD generates extensive peptide and protein sequence coverage without disturbing labile groups, its use is limited to the positive ion mode. However, many analytes are acidic and more readily ionized as negative ions. EDD is the complement of ECD in negative ion mode. EDD has been demonstrated using Fourier transform ion cyclotron resonance (FTICR) and three-dimensional quadrupole ion trap mass spectrometers (QITMS). The work presented here describes EDD in a hybrid linear ion trap/time-of-flight mass spectrometer. This instrument is less expensive and has a higher duty cycle than its FTICR counterpart while offering better resolving power and mass measurement accuracy than the QITMS.
Method
A linear radio frequency ion trap housed within a permanent magnet (rf-ECD cell) is used for the EDD experiments. The rf-ECD cell is part of a hybrid linear ion trap/time-of-flight (LIT/TOF) mass spectrometer (nano-Frontier, Hitachi High Tec., Japan) that utilizes a LIT before the rf-ECD cell for parent ion accumulation and isolation. The parent anions are sent from the LIT to the rf-ECD cell where they are irradiated with energetic electrons (> 10 eV) generated from a tungsten filament. Following the EDD event, product ions are sent to a reflectron-TOF for mass analysis.
Preliminary Data
The peptides FLEEV and FLEEI were used as model analytes for initial experiments. Proof-of-principle results were acquired using 20 eV electrons to irradiate the parent anions for 65 – 80 ms. The electron beam current for the EDD experiments was 3 – 4 ?A, measured on a multi-pole ion guide located before the rf-ECD cell. Performing EDD on the [M – 2H]2- peak of the peptide FLEEV produced odd- and even-elect