Semi-denaturing and SDS-PAGE analysis of outer membrane preparations obtained from A. chroococcum SBUG 1484 cells incubated under nitrogen-fixing conditions. Gel 1: Semi-denaturing PAGE of outer membrane preparations (0 - 72 h cultivation) containing residues of cell wall debris, cyst walls and sarkosyl-insoluble outer membrane components stained for PO activity with p-phenylenediamine at 37°C for 10 minutes in NAc buffer (100 mM, pH 5). Arrows reference p-phenylenediamine oxidizing protein bands 1-3. Molecular weights were estimated using a pre-stained Roti®-Mark BICOLOR marker. Gel 2: Silver-staining of excised and completely denatured p-phenylenediamine active proteins (48 h sample) subsequently analyzed via SDS-PAGE. Examination of molecular weights of extracted proteins was accomplished using a low range molecular weight marker (14 - 66 kDa).