Top-Down Mass Spectrometry for Protein Molecular Diagnostics and Biomarker Discovery

Top-down mass spectrometry differs from the traditional bottom-up approach in that proteins are analyzed directly rather than enzymatically digested prior to analysis. Although the bottom-up approach tends to be faster and more readily implemented, the top-down approach has improved selectivity that enables simultaneous characterization of dynamic and hard-to-predict events such as coding polymorphisms, alternative splicing, and post-translational modifications, promising a clearer picture of biological variation that exists beyond gene translation. With the maturation of multidimensional sample processing procedures, data analysis tools, and "online" liquid chromatography and high-resolution mass spectrometry (LC/MS) technologies, top-down for proteomics investigations has emerged with sensitivity and dynamic range typically associated with peptide workflows. Top-down and bottom-up often provide complementary information; therefore, as the instrumentation used for bottom-up and top-down continues to merge, top-down is becoming more accessible to the general scientific community, allowing scientists to gain a more complete understanding of dynamic living systems.