Protein nanopores such as α-haemolysin and Mycobacterium smegmatis porin A(MspA)can potentially be used to sequence long strands of DNA quickly and at low cost.To provide high-speed sequencing,large arrays of nanopores are required that allow the nanopores to be individually addressed,but current nanopore sequencing methods rely on ionic current measurements and such methods are likely to prove difficult to scale up.