Ion Permeation by a Folded Multiblock Amphiphilic Oligomer Achieved by Hierarchical Construction of Self-Assembled Nanopores

A multiblock amphiphilic molecule <b>1</b>, with a tetrameric alternating sequence of hydrophilic and hydrophobic units, adopts a folded structure in a liposomal membrane like a multipass transmembrane protein, and is able to transport alkali metal cations through the membrane. Hill’s analysis and conductance measurements, analyzed by the Hille equation, revealed that the tetrameric assembly of <b>1</b> forms a 0.53 nm channel allowing for permeation of cations. Since neither <b>3</b>, bearing flexible hydrophobic units and forming no stacked structures in the membrane, nor <b>2</b>, a monomeric version of <b>1</b>, is able to transport cations, the folded conformation of <b>1</b> in the membrane is likely essential for realizing its function. Thus, function and hierarchically formed higher-order structures of <b>1</b>, is strongly correlated with each other like proteins and other biological macromolecules.