MODIFICATION OF DNA DUPLEXES TO SMOOTH THEIR THERMAL-STABILITY INDEPENDENTLY OF THEIR BASE CONTENT FOR DNA-SEQUENCING BY HYBRIDIZATION

The possibility of equalizing DNA duplex stability is essential for th e application of sequencing by hybridization, In this paper we describ e a new strategy to obtain DNA duplexes with a thermal stability indep endent of their base content. Modified C bases have been developed an d incorporated into oligonucleotides. The influence of these modificat ions on duplex stability has been studied by absorption spectroscopy, thus allowing selection of N-4-ethyl-2'-deoxycytidine (d(4Et)C), which hybridizes specifically with natural dG to give a G(4Et)C base pair w hose stability is very close to that of natural AT base pairs, Duplexe s built with AT and/or G(4Et)C base pairs exhibit thermal stabilities independent of their base content in a classical buffer solution, thus enabling control of the stability of DNA hybrids as a function of the ir length only.