Background: OmpC porin is less permeable than OmpF, but there is little difference in channel size.
Results: There are more charged residues in the OmpC channel, and mutating them or increasing ionic strength made it more permeable and OmpF-like.
Conclusion: Charged residues produce the low permeability of OmpC.
Significance: OmpC, produced in a high ionic strength environment, has properties optimized for this environment.
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