Background
MALDI Imaging has a broad range of applications in Omics research. However, a gap exists between desired mass resolution capabilities and the acquisition speed of current instrumentation. We present initial results from the timsTOF flex system; a timsTOF Pro QTOF mounted with a high-throughput, high spatial resolution MALDI source and stage.
Methods
A timsTOF Pro was mounted with a MALDI source and 10 kHz smartBeam 3D laser featuring electronically controlled spot positioning and beam profile for imaging. Performance in ESI mode was evaluated by analyzing a commercially available HeLa digest (Pierce) using DDA PASEF approach. Tissue samples for MALDI-MSI were mounted on conductive glass slides, and coated with matrix using standard protocols on a TM Sprayer (HTX Technologies, Chapel Hill, NC, USA). MALDI ion mobility imaging experiments were acquired on the system at a mobility resolution of 150 1/K0.
Findings
High spectral quality MALDI Imaging data could be acquired at a rate of up to 20 pixels/second in both positive and negative mode. A sagittal rat brain section consisting of approximately 370,000 pixels took ~5 hours to measure. Spatial resolution of 20 µm was confirmed by matching ion signals to specific cells and structures in rat brain. In experiments designed to stress the system, 20 hours of image acquisition or ~1.5 million pixels showed no decline in imaging dataset quality and a mass deviation of RMS 2.06 without lock mass. Trapped ion mobility imaging measurements removed isobaric interferences in lipid imaging.
Proteomics analysis s was used to assess if the dual source design and MALDI Imaging experiments affected LC-MS/MS performance. Injections of 200ng HeLa revealed over 5000 protein groups identified; this figure is maintained over the course of measuring 20 million MALDI pixels.
Conclusion:
The timsTOF fleX allows for fast, high-spatial resolution MALDI acquisition, and robust ESI performance.