Membrane activity of a DNA-based ion channel depends on the stability of its double-stranded structure.

Structural DNA nanotechnology has emerged as a promising method for designing spontaneously-inserting and fully-controllable synthetic ion channels. However, both insertion efficiency and stability of existing DNA-based ion channels leave much room for improvement. Here, we demonstrate an approach to overcoming the unfavorable DNA-lipid interactions that hinder the formation of a stable transmembrane pore. Our all-atom MD simulations and experiments show that the insertion-driving cholesterol modifications, when introduced at an end of a DNA strand, are likely to cause fraying of the terminal base pairs as the DNA nanostructure adopts its energy-minimum configuration in the membrane. We also find that fraying of base pairs distorts nicked DNA constructs when embedded in a lipid bilayer. Here, we show that DNA nanostructures that do not have discontinuities (nicks) in their DNA backbones form considerably more stable DNA-induced conductive pores and insert into lipid membranes with a higher efficiency than the equivalent nicked constructs. Moreover, lack of nicks allows to design and maintain membrane-spanning helices in a tilted orientation within lipid bilayer. Thus, reducing the conformational degrees of freedom of the DNA nanostructures enables better control over their function as synthetic ion channels.

Chaotic Behavior of Ionic Transportation Through Synthetic Ion Channels

Selective ion transportation through synthetic ion channels in polymeric membranes (which mimic natural systems, e.g. excitable cell membranes) is being reported through this article. The synthetic ion channels have been created by swift heavy ion irradiation of polymeric membranes followed by chemical etching. Since, the transportation of sodium and potassium ions of aqueous electrolytes through synthetic ion channels in polyethylene terephthalate depends on the electrophoretic forces present in the electrolyte; these ion channels are referred to as “voltage activated channels”. For a particular range of applied voltage, these channels behave as K-channels while they act as Na-channels in another voltage range. The channels have been found to switch between high and low conduction states referred to as opening and closing of ion channels with applied potential. A mechanism is being proposed to explain the voltage dependent ion selectivity of the channels in both closed and open states. Nonlinear dynamical analysis of ion transportation and current oscillations confirm its chaotic behavior. Their possible applications as ionic switches and ionic flip-flops are discussed.

Controllable synthetic ion channels

The controllable synthetic ion channels with voltage-, ligand- light- and mechano-gating, as well as rectifying behaviours are discussed in regarding to their construction strategies and functions.