A set of four hybrid duplexes formed by antisense oligos, each containing one North-form (3'-endo) locked 1-(1',3'-O-anhydro-β-D-psicofuranosyl)thymine block T at different sites and a matched 15mer RNA, were subjected to the RNase H cleavage reaction, showing how the transmission of the local conformation owing to a single North-locked sugar steers the conformational changes of the four neighbouring nucleotides.