Description_x000D_ General description_x000D_ The BL21(DE3) Chemically Competent strains contain the phage T7 RNA polymerase gene linked to the IPTG-inducible promoter, for use with any expression plasmid containing the T7 promoter._x000D_ Genotype_x000D_ F – ompT hsdSB (rB- mB-) gal dcm (DE3)_x000D_ Application_x000D_ The E. coli strain BL21 (DE3) has been used to express tau 2N4R isoform (aa1–441) and the truncated tau (aa1–421) using pET19b as expression vector._x000D_ Features and Benefits_x000D_ • a transformation efficiency of >1 × 107 cfu/μg._x000D_ • economical prices_x000D_ • offering superior value for everyday protein expression work._x000D_ Components_x000D_ • BL21(DE3) chemically competent cells_x000D_ • pUC 19 transformation control DNA_x000D_ • recovery medium for expression