FIG. 3.
Expression and affinity chromatography purification profiles of the M. tuberculosis antigens expressed in 100 ml of M15/E. coli cultures. Lanes: M and Ms, protein molecular weight markers (M, Kaleidoscope standards; Ms, Sigma Broad range); 1 through 4, aliquots taken at 0, 1, 2, and 3 h, respectively, after induction with 1 mM IPTG; B, total cell lysate before passing through Ni-NTA column; A, total lysate after passing through column; W, wash fractions in 8 M urea buffer (pH 6.5 to 5.9); E1 to E7, eluted fractions in 8 M urea buffer (pH 4.5). The bulk of the recombinant proteins were observed to be eluted in fractions in 8 M urea buffer (pH 4.5). The bulk of the recombinant proteins were observed to be eluted in fractions E2 and E3 (arrows). All the gels were stained with Coomassie brilliant blue, except for C17, which was silver stained.