Two formacetal-linkeddinucleotides TT and TA were synthesized as phosphoramidite building blocks for solid-phase synthesis. Incorporated in a 29-mer DNA, the oligomers P3TT and P3TA were studied with respect to the binding activity towards the Pax6homeodomain. Substitution of the negatively charged phosphodiester by a neutral formacetal linker facilitates the bent conformation of double-stranded