Using nanopores to discriminate between single molecules of DNA

Discrimination and characterization of unlabeled, low copy number DNA molecules may become a central requirement for many future biotechnology applications where low cost, high throughput genomic analysis is essential. To date, approaches to such analysis usually require many copies (femto-moles or more) of DNA that are amplified from a specific small region of DNA. In many cases, preparing this DNA is the rate-limiting step that significantly contributes to the overall cost of the analysis. Recently, new tools and techniques that allow detection and manipulation of single DNA molecules have been reported. These tools may eliminate the necessity for DNA amplification. One example consists of sequence-specific DNA detection using molecular beacons which offer a superior signal-to-background efficiency compared with standard DNA probes, and thus are much more suitable for single molecule detection [1]. Single DNA molecules have also been sorted and sized using electric fields [2] or stretched by electrophoretic force in a specially micro-fabricated cell [3].