Unimolecular Transmembrane Na^(+) Channels Constructed by Pore-Forming Helical Polymers with a 2.3A Aperture

To understand the relationships between channel size and ion selectivity,we have developed a new type of artificial ion channel based on pore-forming helical polymers consisting of phenanthrolineoxadiazole units with a pore aperture 2.3A close to the diameter of the Na^(+)ion(2.04A).Successful preparation of high molecular weight helical polymers(HP1)gives rise to a 4.6 nm long artificial unimolecular transmembrane channel.The transport property of artificial channel HP1 was elaborately investigated by means of vesicle-based kinetic assay and symmetry/asymmetry bilayer membrane(BLM)experiments as well.These results unambiguously demonstrate that HP1 is a Na^(+)-selective channel with extremely high transport activity(EC_(50)=0.017 mol% relative to lipid).Moreover,the Na^(+)/K^(+)selectivity ratio of HP1 reaches 1.9,as determined by asymmetry BLM experiments.Owing to the narrowest 2.3A size constraint so far,HP1 transport naked Na^(+)ion across the membrane,which represents a different Na^(+)transport mode from that of natural Na^(+)channels,which transports partially hydrated Na^(+)ions during transmembrane conduction.This study provides crucial insights on the chemical basis of ion selectivity in the field of ion channels.

Dimensionally confined nanosheets self-assembled through self-shielding multiple hydrogen bonding interactions in aqueous media

Herein,we adopt a simple supramolecular strategy to effectively control the tautomerism of ureidopyrimidinone(UPy)moiety and ultimately realize the complete arrangement of enol configuration.The obtained UPy derivatives containing self-complementary quadruple hydrogen bonding interactions can spontaneously self-assemble towards the formation of well-controlled,self-organized supramolecular nanostructure morphologies in both chloroform and water.The resulting aggregates had been fully characterized by various spectroscopy(absorption,emission)and microscopy(TEM,SEM and AFM)studies.It is anticipated that this study can provide an exact and excellent monomeric unit for controllable and precise supramolecular polymerization.The results achieved here also demonstrate the utility and feasibility of multiple hydrogen bonds to direct the self-assembly of small-molecule building blocks in aqueous media,which provides a strategy for the construction of well-defined and stable supramolecular architectures with chemical functionalities and physical properties as advanced materials for biological applications.