O_R3 operator of bacteriophage λ in a 23 base-pair DNA fragment: Sequence-specific ¹H NMR assignments for the non-labile protons and comparison with the isolated 17 base-pair operator

Sequence-specific ¹H NMR assignments are presented for a non-selfcomplementary 23-base-pair DNA duplex of molecular weight 15,000 daltons, containing the O_R3 repressor binding site of bacteriophage λ as the central core. The NMR techniques used were mainly phase-sensitive two-dimensional NOE and 2Q spectroscopy, the latter to overcome overlap problems within the spectral region of the deoxyribose spin-systems. Direct sequential NOE connectivities are observed between adenine 2H and deoxyribose 1′ protons. We propose the use of these connectivities as a check of the assignments of C1′ and A2 protons, which have independently been derived via other assignment pathways.