2D DIGE analysis of serum after fractionation by ProteoMiner™ beads

Serum is a popular biofluid used for many protein biomarker discovery projects since the collection and processing of serum/plasma is relatively noninvasive and inexpensive. Unfortunately, the downstream analysis of serum/plasma is hampered severely by several high-abundant proteins which often interfere with the separation and detection of many of the proteins of lower abundance. Thus, a number of prefractionation methods have recently been developed with the view to reduce the dynamic range of these proteins. These include both dye- and immunoaffinity-based methods that are specifically designed to remove serum albumin. In this chapter, we describe an alternative method using ProteoMiner™ or Equalizer beads that is aimed at overcoming this problem in serum. This method uses a combinatorial library of hexapeptides bound to beads and works by binding proteins until saturation is reached. Thus, the high-abundant proteins will reach saturation quickly, while the lower-abundant proteins continue to bind. This results in a dramatic depletion of the most abundant proteins, with a concurrent concentration of the middle- to low-abundant proteins.