Time-Resolved
Imaging of High Mass Proteins and Metastable
Fragments Using Matrix-Assisted Laser Desorption/Ionization, Axial
Time-of-Flight Mass Spectrometry, and TPX3CAM
posted on 2022-12-27, 20:10authored byAnjusha Mathew, Joel D. Keelor, Gert B. Eijkel, Ian G. M. Anthony, Jingming Long, Jord Prangsma, Ron M. A. Heeren, Shane R. Ellis
The Timepix (TPX)
is a position- and time-sensitive pixelated charge detector that can
be coupled with
time-of-flight mass spectrometry (TOF MS) in combination with microchannel
plates (MCPs) for the spatially and temporally resolved detection
of biomolecules. Earlier generation TPX detectors used in previous
studies were limited by a moderate time resolution (at best 10 ns)
and single-stop detection for each pixel that hampered the detection
of ions with high mass-to-charge (m/z) values at high pixel occupancies. In this study, we have coupled
an MCP-phosphor screen-TPX3CAM detection assembly that contains a
silicon-coated TPX3 chip to a matrix-assisted laser desorption/ionization
(MALDI)-axial TOF MS. A time resolution of 1.5625 ns, per-pixel multihit
functionality, simultaneous measurement of TOF and time-over-threshold
(TOT) values, and kHz readout rates of the TPX3 extended the m/z detection range of the TPX detector
family. The detection of singly charged intact Immunoglobulin M ions
of m/z value approaching 1 ×
106 Da has been demonstrated. We also discuss the utilization
of additional information on impact coordinates and TOT provided by
the TPX3 compared to conventional MS detectors for the enhancement
of the quality of the mass spectrum in terms of signal-to-noise (S/N)
ratio. We show how the reduced dead time and event-based readout in
TPX3 compared to the TPX improves the sensitivity of high m/z detection in both low and high mass
measurements (m/z range: 757–970,000
Da). We further exploit the imaging capabilities of the TPX3 detector
for the spatial and temporal separation of neutral fragments generated
by metastable decay at different locations along the field-free flight
region by simultaneous application of deflection and retarding fields.