Stable, specific, and reversible base pairing via Schiff base.

We here present a novel covalently linked base pair via Schiff base formation between 5-formyluracil (fU) and 5-aminocytosine (AmC). Formation of the Schiff base linkage proceeds reversibly and does not require any additives. The cross-linked DNA is very stable under denaturing conditions, whereas it completely dissociates upon heating at 90 degrees C. The pairing ability of AmC and fU is very specific and is applicable to the detection of fU, which is the major oxidative lesion of T in DNA. We propose the Schiff base linkage as a new artificial base pairing scheme to create functional DNAs.