Outer surface modification of synthetic multifunctional pores.

The characteristics of pores formed by p-octiphenyl beta-barrels with LWV triads at the outer surface are reported in comparison with the conventional rigid-rod beta-barrels with all-L outer surface. Maintained multifunctionality of tetrameric pores with external LWV triads (inversion of ion selectivity, molecular recognition and transformation) is implicative for intact barrel interior. Increased pore activity supports dominance of high bilayer affinity for W over low affinity for V. Transmembrane p-octiphenyl orientation (from fluorescence depth quenching) supports barrel-stave (rather than toroidal) pores and dominance of transmembrane preference of rigid rods over interfacial preference of W. Destabilization of beta-barrel pores in membranes (from short single-channel lifetimes) and in the media (from 4th-power dependence on monomer concentration) by LWV triads supports dominance of low beta-propensity for W over high beta-propensity for V. The relation between the stability of supramolecular (pre)pores and dependence of activity on monomer concentration is discussed in a more general context.