Diagnostic sequencing of DNA by mass spectrometry

摘要

Since the introduction of matrix-assisted laser desorption/ionization (MALDI)j and electrospray ionization (ESI) in the late 1980s, intact ions from large biomolecules can be generated without fragmentation. As a result, mass spectrometry has been increasingly popular as a tool in genomics and proteomics, as well as in clinical diagnostics. Briefly, ESI usually utilizes a strong electric field at the tip of a spraying nozzle to form charged droplets. These charged droplets shrink by solvent evaporation until highly charged gas phase ions remain. Multiplecharged ions with different charge states are characteristic of ESI ions. On the other hand, MALDI incorporates analyte molecules into selected small molecules that serve as energy absorbent (matrix). When irradiated with a laser pulse, matrix molecules are ejected, carrying out analyte molecules. Gas phase proton transfer between matrix and analyte molecules mainly produces singly charged matrix and analyte ions. Due to the simplicity of the charge-state of its ions, MALDI is more commonly used for the analysis of complex mixtures.