Arrays for protein expression profiling: towards a viable alternative to two-dimensional gel electrophoresis?

Two-dimensional gel electrophoresis (2-DE) is used as a platform method for the measurement of protein expression patterns within cells, tissues or organisms. This approach can support expression profiling of several thousand proteins in multiple samples and as such it is currently unrivaled as a tool for the analysis of protein expression, which is a key component of the rapidly expanding field of proteomics. However, 2-DE has a number of significant limitations and as a consequence, alternative approaches for the measurement of expression of proteins within complex samples are actively being explored. Here we review some existing and emerging methods for protein expression analysis. In particular, we review a range of technologies that might be integrated to support the development of 'arrays' or 'chips' for rapid, high-throughput analysis of protein expression in a manner analogous to the current use of DNA arrays for mRNA expression analysis. We conclude that such separation-independent platforms may ultimately supersede two-dimensional (2-D) gel-based analyses for global protein expression analysis but that before this the technologies might provide important new platforms for diagnostic and prognostic monitoring of diseases.