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 OHB19/23) were complexed with inorganic polyphosphates (polyPs) to create large conductance, voltage activated ion channels in planar lipid bilayers of 1,2-dierucoylphosphatidylcholine. The OHB19/23/polyP channels displayed higher conductance (275 pS vs 100 pS) and significantly poorer selectivity for Ca2+ over Nai 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, OHB19/23 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.