ABSTRACT
I. INTRODUCTION The availability of completed genome sequences of several prokaryotes, viruses, and eukaryotes has transformed biomedical research in a short period of time. Several postgenomic technologies including SAGE (serial analysis of gene expression), [1] and cDNA microarrays [2,3] have been developed to globally and quantitatively measure gene expression at the mRNA level. However, no strict linear correlation between gene expression and the protein complement or ‘‘proteome’’ of a cell has been determined. In fact, many studies have shown quite a poor correlation between mRNA and protein expression levels [4-7]. Proteins, not genes, are responsible for most functions in the cell; thus, studying the cellular proteome can provide a picture of the protein environment at any given time.
