Effect of morphine analogues on the conformational state of polyriboadenylic acid in solution: an NMR study.

The interaction of morphine analogues with polyadenylic acid in aqueous solution at pH 7 has been investigated. The NMR spectra measured at several temperatures were shown to give evidence of a lowering of the transition temperature from the helix to the random-coil structure. The measured chemical shifts and relaxation times were interpreted in terms of an ionic interaction between the + N - CH3 group of the drug and phosphate residue of the polynucleotide.