One‐ and two‐dimensional 1H‐NMR investigations of two 19‐base‐pair analogues of the tet operator

Abstract
Two 19-base-pair oligodeoxynucleotides, analogues of one of the operators which specifically bind the repressor protein in the regulatory part of the transposon Tn10 tetracycline-resistance (tet) determinant, have been studied by 1H-NMR spectroscopy. The analogues contain a mismatch in the central base pair of the double helix (T.cntdot.T or A.cntdot.A). The imino protons have been assigned to the base pairs by one-dimensional NOE measurements, and the thermally induced transition from the duplex to the single strand has been followed. The cytidine amino resonances have been assigned by means of two-dimensional NOE spectroscopy in H2O. Two-dimensional phase-sensitive NOE and magnitude-correlated spectra have been recorded in 2H2O; all nonexchangeable protons, with the exception of some of H5'', H5'''' protons, have been assigned. The NMR data made it possible to carry out a qualitative analysis of the structures of both oligodeoxynucleotides. The general structures close to B-DNA, show irregularities in the mismatch areas.

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