Biomimetic Nanopores with Amphoteric Amino Acid Groups. Effects of a pH Gradient on the Ionic Conductance and Selectivity

Biological ion channels have been an inspirational source in the development of new devices in a variety of biotechnological and analytical applications. During the last years, synthetic nanopores have been carefully engineered to mimic distinctive features of biological ion channels. Conductance in the pS–nS range, pH-dependent ion selectivity, fluctuations of current between open and closed states, flux inhibition caused by protons or divalent cations, current rectification, among others are found both in synthetic and biological channels. Thus, the comprehension of the mechanisms by which biological channels regulate the transport of ions and the electric signal transduction at the molecular level is crucial for building ionic circuits in the growing field of nanofluidics. We show here that gold coated polymeric nanopores modified with amino acid (Cysteine) chains are able to imitate the electrical responses of the OmpF porin, a wide channel found in the external membrane of the bacteria Escherichia Coli.