Flexible oligocholate foldamers as membrane transporters and their guest-dependent transport mechanism

Abstract

Dimeric, trimeric, and tetrameric oligocholates with flexible 4-aminobutyroyl spacers caused the efflux of hydrophilic molecules such as carboxyfluorescein (CF) and glucose from POPC/POPG liposomes. Transport was greatly suppressed across higher-melting DPPC membranes. Lipid-mixing assays and dynamic light scattering (DLS) indicated that the liposomes were intact during the transport. Kinetic analysis supported the involvement of monomeric species in the rate-limiting step of CF transport, consistent with a carrier-based mechanism. Glucose transport, on the other hand, displayed a highly unusual zero-order dependence on the oligocholate concentration at low loading of the transporter. Different selectivity was observed in the oligocholate transporters depending on the guest involved.