Ion Channels Formed by Biomimetic Oligo-(R)-3-hydroxybutyrates and Inorganic Polyphosphates in Planar Lipid Bilayers

Biomimetic monodisperse oligomers of ( R )-3-hydroxybutyrate ( M n 1670, M w / M n 1.2) (referred to as OHB 19/23 ) were complexed with inorganic polyphosphates (polyPs) to create large conductance, voltage-activated ion channels in planar lipid bilayers of 1,2-dierucoylphosphatidylcholine. The OHB 19/23 /polyP channels displayed higher conductance (275 pS vs 100 pS) and significantly poorer selectivity for Ca 2+ over Na + than channels formed by polyPs with polymers of ( R )-3-hydroxybutyrate (PHBs) of 120−140 monomer units (>90:1 vs 4:1), suggesting that the oligomer channels are less well organized. In the absence of polyPs, OHB 19/23 formed channels only at 100-fold higher concentrations, and the channels were essentially nonselective open pores with fluctuating conductance that closed only rarely. The results suggest that polyPs serve as voltage sensors and have a major role in cation selection, whereas OHBs serve principally as solvating agents. It may be concluded that monodisperse biomimetic OHBs and polyPs can be used effectively to form voltage-activated artificial ion channels of limited cation selectivity.