Analysis of loss and mutation of the recombinant plasmid from <i>E. coli</i> BL21(DE3)/pET-20b(+)-<i>pul</i>.

<p>(A) Restriction enzyme analysis of the recombinant plasmid pET-20b(+)-<i>pul</i>. Lane M: DNA Marker, Lane 1: double digestion of pET-20b-<i>pul</i>; (B) Plasmid stability during cryopreservation; (C) SDS-PAGE analysis of PUL expression in <i>E. coli</i> BL21(DE3)/pET-20b(+)-<i>pul</i> strain. Lane M: protein molecular weight marker, Lane 1: total protein of newly transformed strain, Lane 2: total protein of originally constructed strain.