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Figure 1. Peptide degradation by bacterial proteinases. (A) S. aureus cells (6.4 x 108 cells/mL PBS) were incubated with the dhvar peptides for 4 hrs at 37°C. Samples were analyzed on high-density SDS-PAGE gels in combination with Coomassie Brilliant Blue staining. Lane 1, dhvar1 (200 µg/mL) not incubated with bacteria; lanes 2–4, samples taken at 15, 120, and 240 min, respectively. A peptide band with lower molecular weight gradually appeared over time, indicating progressive degradation. Incubation of S. mutans with dhvar1 and dhvar2 showed similar patterns (not shown). (B) Lane 1 contained the native peptide dhvar1 (200 µg/mL). Lane 2: Dhvar1 incubated with P. gingivalis cells (1.6 x 106 cells/mL PBS) for 60 min at 37°C. Lane 3: Dhvar1 incubated (4:1) with supernatant of 6 days’ cultured P. gingivalis (five-minute incubation). Incubations with P. aeruginosa showed similar results (not shown).
