. Surface induced dissociation (SID) has emerged as an effective tool for probing the topology of protein complexes in the field of native mass spectrometry (nMS). SID has the unique advantage of efficiently cleaving the interfaces of noncovalent protein complexes to yield monomer subunits as well as small order oligomers. Additionally, SID products typically retain compact/highly structured conformations such that ion mobility measurements coupled with SID can be used to gain insights into protein subunit structure through collision cross section (CCS) measurements. This TR&D aims to improve SID technology across multiple mass analysis platforms that are used in the nMS field (namely quadrupole-time-of- flight (QTOF), OrbitrapTM, and Fourier transform ion cyclotron resonance (FTICR) platforms). Current SID devices span 3-4 cm of an instrument?s ion path with at least ten DC electrodes. These electrode voltages can be tuned to direct ions toward an off-axis surface (relative to the ion path within an instrument for the activating ion-surface collision and subsequent collection of product ions back onto the original ion trajectory axis. Lenses may also be tuned to guide ions through the device without activation, allowing for standard MS experiments to be conducted (so-called ?flythrough? mode).
Aim 1 of this TR&D is to simplify the tuning of SID experiments while retaining or improving ion transmission efficiencies in both SID and ?fly-through? experiments. A new SID device containing an on-axis collision surface and ion carpet will be developed to require fewer electrodes than current SID devices, thereby simplifying tuning requirements for SID. The radial-focusing nature of the ion carpet array is expected to assist ion transmission efficiencies. The device will be implemented in a prototype higher resolution QTOF.
Aim 2 will adopt advances made in Aim 1 to improve current SID performance within Orbitrap platforms for high resolution nMS experiments. There is also an SID acceleration voltage limit of roughly 70 V for current Orbitrap configurations. Collaboration with Thermo Fisher will facilitate progress by providing the schematic information necessary to incorporate independent power supplies into electronic boards on the QExactive+ EMR platform at OSU and QExactive HF UHMR platform proposed for purchase. This collaboration will also facilitate adapting technology developed from Aim 1 into the ion optics within Orbitrap Exactive platforms.
Aim 3 focuses on improving SID technology in an FTICR platform. Currently, this platform has a maximum quadrupole mass isolation limit of m/z 6000, which is too low for selection of larger protein complexes. There is currently a diminished performance in the collection of collision induced dissociation fragments due to the original collision cell space being split between an SID device and truncated collision cell. Both of these shortcomings will be addressed through instrument redesign in collaboration with the vendor (Bruker) as described in Aim 3.
