Correlation between observed emPAI values and independently measured protein copy numbers per cell. Protein abundances in the E. coli cytosol as measured by the emPAI approach correlate well with protein copy numbers per cell measured independently by isotope dilution using spiked E. coli BW25113 cells containing 40 proteins with known amounts . A dynamic range of approximately 4 orders of magnitude of protein copy numbers per cell is covered. The Pearson correlation coefficient is 0.84 with a p-value < 10-10 for logarithmized and 0.52 (p-value < 10-4) for non-logarithmized variables.
Ishihama et al. BMC Genomics 2008 9:102 doi:10.1186/1471-2164-9-102