High Mass Resolution MALDI-imaging MS Using JMS-S3000 SpiralTOF and msMicroImager
Imaging mass spectrometry using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-Imaging) has been expanded during the last decade in biological applications, to assess the distribution of proteins, peptides, lipids, drugs, and metabolites in a tissue specimen. In MALDI-Imaging measurements, a laser irradiation point was scanned on a sample surface to acquire a mass spectrum at each point. Analyzing the mass spectra with two-dimensional position information, localization of compounds with inherent molecular weights can be visualized or the mass spectra for certain regions of interests (ROIs) can be created. The JMS-S3000 SpiralTOF (Fig. 1) is a MALDI-TOFMS, which utilizes the JEOL patented spiral ion optical system. It has a 5-10 times longer flight path than the typical reflectron type MALDI-TOFMS. As a result, it can achieve high mass-resolution to separate peaks that have the same nominal mass but have different exact masses (isobaric separation). On the other hand, there are some issues for analyzing high mass resolution and high lateral resolution MALDI-Imaging raw data with common imaging software options such as Biomap.
- It is difficult to handle the large size raw data, especially for a large number of mass spectrum points.
- It is difficult to use the detailed information from high mass resolution MALDI-Imaging by extracting mass images manually. Furthermore, peaks observed in the mass spectra cannot be identified by its origin, such as samples, matrix compounds or surface contaminations, before drawing the mass images.
- A lack of function to overview a large number of mass images.
The JEOL msMicroImager software for high mass resolution MALDI-Imaging raw data was designed to resolve all of these issues.