Why high mass-resolving power is required for MS imaging
MALDI MS imaging was initially developed to focus on high molecular weight compounds such as proteins and peptides. However, with the expanding applications of MALDI MS imaging, the interests have shifted to include smaller molecules such as lipids, pharmaceuticals, and pharmaceutical metabolites. Conventional MALDI - reflectron TOFMS has difficulty discerning small molecule signals from matrix molecules. In the case of MALDI MS imaging, signals from unwanted molecules on the specimen surface will often interfere with signals from the target analytes. High selectivity by means of high mass-resolving power is essential for obtaining reliable target analyte spatial distributions.
The SpiralTOF™-plus 3.0 with its high mass-resolving power is indispensable for MALDI MS imaging.
A tissue section is placed on an ITO-coated glass slide, and matrix solution is sprayed onto the surface.
The specimen is moved beneath the focused laser beam to create a time dependent series of mass spectra where each time corresponds to a specific spatial location.
Analysis of the data allows the researcher to visualize the spatial distribution of specific compounds on the sample surface.
Mass spectrometry imaging data can be analyzed with the JEOL msMicroImagerTM software (optional) or converted to a common data format imzML which allows data analysis by SCiLS Lab MVS (optional) or other third-party software such as BioMap.
FINE-AI Filter: Noise Filtering Using AI (Machine Learning) Technology
Our newest MS imaging data processing software msMicroImagerTM version 3 (optional) is now equipped with FINE-AI Filter, a noise filtering technology that uses AI (machine learning). This new FINE-AI Filter originates from the JEOL LIVE-AI (Live Image Visual Enhancer-AI) technology developed for our scanning electron microscopes (SEM), which was re-optimized for MS imaging and implemented to achieve significant improvements to the quality of MS images.
Mass Spectrometry Imaging Analysis of Lipids in Mouse Brain Tissue Section
Mouse brain sections contain a variety of lipid classes. A mass spectrum obtained from a tissue section is highly complex, especially in the region of m/z 700 - 1,000. Many of the peaks in the mass spectrum are less than 10% of the base peak, representing minor components. MALDI MS imaging of lipids requires a mass-resolving power high enough to separate the minor peaks from interferences. The bottom mass spectrum below shows the expansion of m/z 820 - 823. Many peaks were separated from each other by less than 0.1 u. The high mass-resolving power of the SpiralTOF™-plus 3.0 clearly separated these isobaric peaks, thus allowing the elucidation of 4 lipid elemental compositions. Moreover, each lipid clearly showed a different spatial distribution. Elucidation of elemental compositions and accurate determination of spatial distributions for each lipid would be difficult with a conventional reflectron TOFMS with moderate mass-resolving power.
By applying the AI noise filter, FINE-AI Filter, MS images of even higher quality can be obtained.
PE: Phosphatidyl ethanolamine, PC: Phosphatidyl Choline, GalCer: Galactosylceramide. Separation of isobaric ions and their MS images processed with FINE-AI Filter. This data was acquired in a joint research project with the Mass Spectrometry Group, Project Research Center for Fundamental Sciences, Graduate School of Science, Osaka University. The tissue section specimen was provided by Awazu Laboratory, Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University.