Rosetta™ (DE3) Competent Cells - Novagen Rosetta host strains are BL21 derivatives designed to enhance the expression of eukaryotic proteins that contain codons rarely used in E. coli. - Find MSDS or SDS, a COA, data sheets and more information. Rosetta : Novagen: Rosetta host strains are BL21 lacZY (Tuner™) derivatives designed to enhance the expression of eukaryotic proteins that contain codons rarely used in E. coli. These strains supply tRNAs for the codons AUA, AGG, AGA, CUA, CCC, GGA on a compatible chloramphenicol resistant plasmid. BL21 (DE3) Expression from T7 promoter, tight regulation: BL21 (DE3) pLysS: Expression from T7 promoter with codon bias correction: BL21 codon plus, Rosetta: Improved disulphide bond formation: Origami: Fast cloning (due to quick cell growth) Mach1 Escherichia coli strain BL21 is one of the widely used bacterial hosts for high-level recombinant protein production and for other applications. Here, we present the complete genome sequence of a commercial version of the Escherichia coli BL21 strain. We utilized the expression of the N-terminal His-tagged kinases in BL21 (DE3) E. coli strain for baseline comparison with four different expression improvement techniques: the addition of external folding chaperones and using the specialized strains: Rosetta, BL21 (DE3) pLysS, and Arctic Express. A one-way ANOVA with Dunnett's multiple comparison test was employed to evaluate differences in expression levels of recombinant protein between Evo21(DE3) and other expression hosts. P values uyMq.