document: For coexpression of QβCP, mCherry protein and the 3 WJ RNA scaffold, pCDFDuet-1-QβCP-mCherry (stpR) and pET28-b(+)-3WJ (KanR) were transformed into E. coli BL21 cells (HIT-21®, RBC, USA) for expression. E. coli BL21 cells harbouring the plasmids were grown in either LB broth supplemented with antibiotic (streptomycin) at 50 μg/mL. Starter cultures were grown for 18 h at 37 ℃ and were used to inoculate 1 L of expression culture. IPTG (1 nM) was used as a protein expression reagent at an OD600nm