Possible conformation of amphotericin B dimer in membrane-bound assembly as deduced from solid-state NMR.

Aiming for structural analysis of amphotericin B (AmB) ion-channel assemblies in membrane, a covalent dimer was synthesized between (13)C-labled AmB methyl ester and (19)F-labled AmB. The dimer showed slightly weaker but significant biological activities against fungi and red blood cells compared with those of monomeric AmB. Then the dimer was subjected to (13)C{(19)F}REDOR (Rotational-Echo Double Resonance) experiments in hydrated lipid bilayers. The obtained REDOR dephasing effects were explained by two components; a short (13)C/(19)F distance (6.9Å) accounting for 23% of the REDOR dephasing, and a longer one (14Å) comprising the rest of the dephasing. The shorter distance is likely to reflect the formation of barrel-stave ion channel.