Negative incremental resistance induced by calcium in asymmetric nanopores.

Siwy, Zuzanna S; Powell, Matthew R; Kalman, Eric; Astumian, R Dean; Eisenberg, Robert S · Nano Lett · 2006

basic_science · Level V

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Abstract

Single polymer nanopores with permanent surface charges act as rectifiers of ionic current. The pores are tapered cones with narrow openings of several nanometers and wide openings of approximately 1 mum. The pores are cation-selective, and in symmetric solutions of potassium chloride they rectify the flow of potassium ions from the small opening toward the wide opening. Millimolar concentrations of calcium reverse the rectification, and a negative incremental resistance is observed. These observations can be interpreted by a model containing flashing ratchets.

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