Fig 1.

Illustration and definition of the linked and unlinked immunogens. (A) A cartoon illustrating the disulfide bonds between adjacent outer membrane proteins formed by the cross-linking agent 3,3′-dithiobis[sulfosuccinimidyl propionate] (DTSSP) in the linked immunogen. The disulfide bonds were reduced through treatment with dithiothreitol (DTT) to form the unlinked immunogen. (B) To determine if reduction of disulfide bonds in the linked immunogen was successful, SDS-PAGE gel electrophoresis was done under nonreducing conditions followed by Western blotting. Omp9 is confined to the stacking gel of the lane containing the linked immunogen (l). The migration of Omp9 to its expected molecular mass of 40 kDa and the lack of additional bands in the unlinked immunogen (u) demonstrate that in the linked immunogen the reduction of the disulfide bonds to produce the unlinked immunogen was successful.