Development of an unnatural base pair for efficient PCR amplification.

An unnatural base pair system could expand the genetic alphabet, enabling the site-specific incorporation of extra, functional components into nucleic acids and proteins. We developed an unnatural base pair between 7-(2-thienyl)imidazo[4,5-b]pyridine (denoted by Ds) and 2-nitropyrrole (denoted by Pn), which specifically and efficiently functions in DNA amplification by PCR. After 20 cycles of PCR, the mutation rate of the Ds-Pn pair in an amplified DNA fragment was approximately 1%. The Ds-Pn pair system in combination with other unnatural base pairs could be useful for DNA/RNA-based biotechnology.