Application of MALDI Mass Spectrometry to Proteomics Discovery
MALDI Mass Spectrometry (MS) is a proven analytical platform for proteomics discovery that offers excellent sensitivity and rapid analysis time. In one single experiment, scientists are able to obtain information on a wide range of compounds, known and unknown, without the need for prior labeling. The MALDI source is especially well suited to proteomics because large molecules such as proteins, peptides and lipids can be difficult to analyze without damaging their structure. The soft ionization process of MALDI provides the ability to study intact bio-molecules and when combined to the power of tandem mass spectrometry offers the analytical resolution needed to explicit complex molecular structures.
How MALDI MS Imaging Changes our Understanding of Biological Composition
By using Mass Spectrometry data to create molecular images scientists are able to visualize the spatial distribution of proteins and other bio-molecules. Thanks to the wide dynamic range of Mass Spectrometers, each experiment actually produces a multitude of images and the ability to visualize multiple species at once.
In the following example, a sagital section of a rat brain has been analyzed by MALDI MS Imaging to produce high resolution maps for species with mass range <1,000 Daltons. Each specie is characterized by its m/z (mass/ion charge) ratio and an imaging software is used to render relative concentration based on a luminosity gradient (Images A-F). Using the same data, a user can also produce a multicolor image (Image G) where one specie is represented in blue and the other in red, while still using a gradient to render relative concentration.
Further analysis is done to identify species of interest and this information can then be used in future work to formally identify specific species. In the images below (H-J and K-N) different lipids have been identified. From these images, one can clearly see that M 385.4 [Cholesterol – H]+ is only present in certain areas of the brain, whereas M 429.3 [Vitamin E –H]+ is present throughout the tissue. An optical microscope image of the tissue (O) is used to verify the correspondence of Mass Spectrometric data and with histological data.