MALDI technique & FLOW CYTOMETRY technique Coursework

MALDI technique & FLOW CYTOMETRY technique - Coursework Example (2) ionization of sample components to produce ions, (3) separation of ions by electromagnetic field to their mass-to-charge ratios, (4) detection of ion signals and, (5) processing of the signals into mass spectra. The ionization of the analytes is a crucial step in mass spectrometry. Two methods are used: electron spray ionization and matrix-assisted laser desorption ionization (MALDI) (Figure 1). In MALDI, the analyte is mixed with matrix, molecules that have strong absorbance at the laser wavelength, and placed onto a metal plate (Karas, Bachmann, & Hillenkamp, 1985). A laser beam is then introduced which results in a burst of ions. The presence of the matrix refreshes the laser burst, and enhances the isolation of the sample ions. Protein and peptide analyses are the most common applications of MALDI, with the most number of technical developments in the past years (Hillenkamp & Katalinic, 2007). MALDI is the leading application for proteomics profiling and imaging. Other analytes studied are nucleic acids, glycans, lipids, and synthetic polymers. Each of these analytes may have limitations in their analysis due to their structural properties, which can interfere with the ionization efficiency. The spatial distribution of drugs, metabolites, and proteins in intact tissues is also made possible with imaging mass spectrometry (Caldwell & Caprioli, 2005). MALDI-MS is therefore a valuable technique that can address a broad range of applications in the biomedical field. Since MALDI-MS tissue profiling permits the detection of more than a thousand peptides and proteins from many tissue types, it is very useful in detecting disease processes. Tissue profiling and imaging permits the direct acquisition of mass spectra from intact tissues that are either freshly prepared or come from tissue storage banks (Djidja, et al., 2010). Recently, tissue blocks that have been embedded in paraffin were used in protein profiling of several cancers. These studies showed that