The present invention provides novel compositions, methods and apparatus for DNA sequencing that can be performed, e.g., in a two-electrode chamber. The present invention also provides a method for sequencing a nucleic acid comprising immobilizing a plurality of complexes comprising a target nucleic acid, a primer nucleic acid, and a polymerase onto a surface, contacting the surface with a plurality of charged particles comprising a nucleotide phosphate by applying an electric field, reversing the electric field to transport unbound charged particles away from the surface, and detecting the incorporation of a nucleotide phosphate into a single molecule of the primer nucleic acid.