ABSTRACT
Human serum is frequently used in proteomics analysis for the discovery of new disease markers, drug targets, or studying protein expression patterns. This body fl uid represents the most complex sample of the human proteome, composed of homeostatic blood proteins as well as tissue leakage proteins.1 Diffi culties arise in the proteomic analysis of serum due to the extreme concentration range of target proteins over 10 to 12 orders of magnitude. High-abundant proteins such as albumin, IgG, transferrin, haptoglobin, IgA, and alpha1-anti-trypsin represent up to 85% of the total protein mass in serum (Figure 5.1). These major protein constituents interfere with identifi cation and characterization of important moderate-and low-abundant proteins by limiting the dynamic range of mass spectral and electrophoretic analysis. During protein isolation, separation, and analysis, these six proteins often mask the detection of the more important low-abundant proteins that are of high interest as biomarkers of disease or drug targets. In one-and two-dimensional gel electrophoresis (1DGE and 2DGE), for example, the spots or bands due to these six highly abundant proteins, as well as their fragments, often overlap or completely mask large regions of the gel, making detection of the myriad low-abundant proteins very diffi cult, if not impossible. Moreover, proteomic analysis methods commonly include an electrophoretic or chromatographic separation step which, of course, has a fi nite mass loading tolerance. The presence of a large quantity of high-abundant proteins limits the mass load of targeted proteins that can be initially sampled by these separation methods.
