(179b) A Bias-Free Method for Concentrating Proteins

Human samples for protein profiling often are pretreated to reduce their dynamic range.   Common methods include immunodepletion (such as Agilent’s MARS column) or concentration-leveling (such as Bio-Rad’s ProteoMiner).  In either case, the proteins recovered from their pretreatment benefit substantially from concentration.

We first review existing methods to perform this concentration.  These include precipitation with trichloroacetic acid, total precipitation with large acetone volumes, use of membrane concentrators, and many others.  All of these have inherent biases, often to very dilute species and those of low molecular weight, such as peptides.

Presented here is a bias-free electrophoretic method to perform such sample concentrations.  Both theory and experiment are included; the emphasis is on physical principles rather than mathematical details.