Instrumentation
Instrumentation
The goal of the lab is to advance electron transfer dissociation (ETD) equipped mass spectrometer instrumentation. There are two sub-categories to this goal: (1) upgrading and optimizing mass spectrometer equipment which is already capable of performing ETD, and (2) adapting additional mass spectrometer equipment to be compatible with ETD. There have already been two significant successes - one for each sub-category. During the late spring of 2006, the lab completed a project that had the goal of converting non-dissociated electron transfer (ET) products into c and z-type product ions (i.e. the typical ETD product ions). Graeme McAlister adapted the instrument (an LTQ equipped with a prototype Thermo Electron ETD package) to do gentle CAD of the electron transfer product. At low activation energy, the ET product ions could be converted in c and z-type ions without generating typical CAD ions, which would have cluttered the spectra. Danielle Swaney demonstrated that by adding in this additional activation step, she was able to generate additional fragment ions and produce spectra that were far informative.
In the fall of 2006, Graeme McAlister adapted an LTQ-Orbitrap hybrid mass spectrometer to allow for ETD. Mass analysis with an Orbitrap produces spectra that are significantly more resolved and with better mass accuracy. Do to spatial complications; it wasn't possible to mount a CI source on the rear of the instrument (i.e. how the current LTQ's have been adapted to allow for ETD). Instead, Graeme used the same atmospheric pressure inlet, on the front of the instrument, to inject both the cations and the reagent anions. To utilize the same inlet for both ions, the sources had to be pulsed. This work drew heavily from previous research done by the McLuckey group at Purdue. The resulting spectra, which were significantly more resolved and had much better mass accuracy, allowed for better fragment identification. In particular highly charged fragment ions could now be identified which would have been impossible with QLT mass analysis.