© ITSDESIGNNET/ISTOCKPHOTO.COMThe complex, ever-changing multitude of proteins present in a cell or tissue at any given time, referred to as the proteome, is difficult to capture and describe. Molecular biologists have a variety of tools at their disposal to study proteins, but arguably none is more powerful for the comprehensive analysis of proteins present in a complex sample than mass spectrometry.
Traditionally, researchers have used one of two mass spec–based approaches to tease apart the complexities of the proteome: a discovery-based strategy to identify as many proteins as possible, and a targeted approach to accurately quantify a few select proteins of interest. Regardless of the method used, researchers typically begin by chopping up the proteins in their sample using enzymes that slice them at specific amino acid sequences into peptides of about 8–22 amino acids, depending on the enzyme used. The resulting peptides are then separated by liquid chromatography and loaded, as they elute, into a mass spectrometer, which converts them to ions in a gas phase. The instrument measures the mass-to-charge (m/z) ratios of the ions and creates mass spectra that report the abundance of ...
