The 5-chlorouracil:7-deazaadenine base pair as an alternative to the dT:dA base pairElectronic supplementary information (ESI) available. See DOI: 10.1039/c6ob02274j

5-Chloro-2′-deoxyuridine as a possible component of a chemically modified genome has been discussed in terms of its influence on duplex stability and DNA polymerase incorporation properties. The search for its counterpart among different deoxyadenosine analogs (7-deaza-, 8-aza- and 8-aza-7-deaza-2′-deoxyadenosines) showed that the stable duplex formation as well as the synthesis of long constructs, more than 2 kb, were successful with the 5-chloro-2′-deoxyuridine and 7-deaza-2′-deoxyadenosine combination and with Taq DNA polymerase. The 5-Cl-dU:7-deaza-dA base pair can be a substitute for the dT:dA base pair in an enzymatic replication process of 2 kb DNA.