SDS–PAGE analysis for recombinant protein 14-3-3-ZsGreen in recombinant E.coli JM107. M: molecular mass standard protein; 1: E.coli JM107 control; 2: the expression of recombinant E.coli JM107 containing pQE-Ka induced by IPTG; 3–7: the expression of recombinant E.coli JM107 containing pQE-ZsGreen induced by IPTG for 0, 1, 3, 5, and 7 h, respectively.