Lucigen’s E. cloni EXPRESS BL21(DE3) Electrocompetent Cells are the first to offer high efficiency cloning and high level protein expression in the same cell. Cloning efficiencies are increased 25-1,000 fold relative to competitors’ preparations of BL21 cells, which is essential for construction of complex expression libraries. The unprecedented transformation efficiency of E. cloni EXPRESS Electrocompetent Cells (> 5 × 10^9 cfu/µg) eliminates the need for plasmid transfer from the cloning strain to the expression strain, saving days of work in a typical cloning and expression experiment. E. cloni EXPRESS cells are also available as chemically competent cells. With a transformation efficiency of >1 × 10^7 cfu/µg and very economical prices, EXPRESS Chemically Competent Cells offer superior value for everyday protein expression work.