MALDI imaging

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MALDI MS image shows distribution of m/z 616 in a whole-body tissue section of a rat. m/z 616 corresponds to the mass of heme b.

MALDI imaging is the use of matrix-assisted laser desorption ionization as a mass spectrometry imaging[1] technique in which the sample, often a thin tissue section, is moved in two dimensions while the mass spectrum is recorded.[2]

Mechanism of MALDI[3][edit]

  1. The peptides are mixed with a matrix solution on a plate. This matrix is a small organic molecule that has strong absorbance at the laser wavelength and is highly sublimable.
  2. A laser beam is introduced to the plate so that ions are produced at every pulse. This is advantageous as it produces shot-to-shot reproducibility.
  3. The ionic peptides travel in the tube towards the detector. The peptides that have lower molecular weight will travel faster and vice versa and will be detected by the detector at the end of the tube.


Target for MALDI imaging with two conductive-surface microscope slides.

MALDI imaging mass spectrometry involves the visualization of the spatial distribution of proteins, peptides, drug candidate compounds and their metabolites, biomarkers or other chemicals within thin slices of sample such as animal tissue or plant.[4][5][6][7][8] It is a promising tool for putative biomarker characterisation and drug development. Initially scientists take tissue slices mounted on microscope slides and apply a suitable MALDI matrix to the tissue, either manually or now automatically. Next, the microscope slide is inserted into a MALDI mass spectrometer. The mass spectrometer records the spatial distribution of molecular species such as peptides, proteins or small molecules. Suitable image processing software can be used to import data from the mass spectrometer to allow visualisation and comparison with the optical image of the sample. Recent work has also demonstrated the capacity to create three-dimensional molecular images using the MALDI imaging technology and co-registration of these image volumes to other imaging modalities such as magnetic resonance imaging (MRI).[9][10]

Commercial instruments[edit]

Currently, the following vendors in the field of MALDI imaging mass spectrometry offer commercial instruments:[11]

Available software[edit]

There are some free software packages available for visualization and mining of MALDI imaging data, as Biomap (Novartis), Datacube Explorer (AMOLF),[12] EasyMSI, Mirion, MSiReader (free, NCSU).[13] In addition the following commercial software suites for MALDI imaging are available: Quantinetix, MALDIVision, SCiLS Lab

See also[edit]


  1. ^ McDonnell LA, Heeren RM (2007). "Imaging mass spectrometry". Mass spectrometry reviews 26 (4): 606–43. doi:10.1002/mas.20124. PMID 17471576. 
  2. ^ Chaurand P, Norris JL, Cornett DS, Mobley JA, Caprioli RM (2006). "New developments in profiling and imaging of proteins from tissue sections by MALDI mass spectrometry". J. Proteome Res. 5 (11): 2889–900. doi:10.1021/pr060346u. PMID 17081040. 
  3. ^ "Matrix-assisted Laser Desorption/Ionisation (MALDI)".  
  4. ^ Caldwell RL, Caprioli RM (2005). "Tissue profiling by mass spectrometry: a review of methodology and applications". Mol. Cell Proteomics 4 (4): 394–401. doi:10.1074/mcp.R500006-MCP200. PMID 15677390. 
  5. ^ Reyzer ML, Caprioli RM (2007). "MALDI-MS-based imaging of small molecules and proteins in tissues". Current Opinion in Chemical Biology 11 (1): 29–35. doi:10.1016/j.cbpa.2006.11.035. PMID 17185024. 
  6. ^ Woods AS, Jackson SN (2006). "Brain tissue lipidomics: direct probing using matrix-assisted laser desorption/ionization mass spectrometry". The AAPS journal 8 (2): E391–5. doi:10.1208/aapsj080244. PMID 16796390. 
  7. ^ Stoeckli M, Staab D, Schweitzer A (2006). "Compound and metabolite distribution measured by MALDI mass spectrometric imaging in whole-body tissue sections". International Journal of Mass Spectrometry 260 (2-3): 195–202. doi:10.1016/j.ijms.2006.10.007. 
  8. ^ Khatib-Shahidi S, Andersson M, Herman JL, Gillespie TA, Caprioli RM (2006). "Direct Molecular Analysis of Whole-body Animal Tissue Sections by Imaging MALDI Mass Spectrometry". Analytical Chemistry 78 (18): 6448–6456. doi:10.1021/ac060788p. PMID 16970320. 
  9. ^ Andersson M, Groseclose MR, Deutch AY, Caprioli RM (2008). "Imaging Mass Spectrometry of Proteins and Peptides: 3D Volume Reconstruction". Nature Methods 5 (1): 101–108. doi:10.1038/nmeth1145. PMID 18165806. 
  10. ^ Sinha TK, Khatib-Shahidi S, Yankeelov TE, Mapara K, Ehtesham M, Cornett DS, Dawant BM, Caprioli RM, Gore JC (2008). "Integrating Spatially Resolved Three-Dimensional MALDI IMS with in vivo Magnetic Resonance Imaging". Nature Methods 5 (1): 57–59. doi:10.1038/nmeth1147. PMC 2649801. PMID 18084298. 
  11. ^ MALDI-MSI Interest Group. "". Retrieved 21 October 2013. 
  12. ^ Klinkert, I.; Chughtai, K.; Ellis, S. R.; Heeren, R. M. A. (2014). "Methods for Full Resolution Data Exploration and Visualization for Large 2D and 3D Mass Spectrometry Imaging Datasets". International Journal of Mass Spectrometry 362: 40–47. doi:10.1016/j.ijms.2013.12.012.  edit
  13. ^ Robichaud, G.; Garrard, K. P.; Barry, J. A.; Muddiman, D. C. (2013). "MSiReader: An Open-Source Interface to View and Analyze High Resolving Power MS Imaging Files on Matlab Platform". Journal of the American Society for Mass Spectrometry 24 (5): 718–721. doi:10.1007/s13361-013-0607-z. PMID 23536269.  edit

External links[edit]