Binding of a porphyrin conjugate of Hoechst 33258 to DNA. II. NMR spectroscopic studies detect multiple binding modes to a 12-mer nonself-complementary duplex DNA

We have probed by H-1 NMR spectroscopy the molecular basis of the interacti on between Hoechst 33258 conjugated to a des-metalloporphyrin and a non sel f-complementary duplex DNA sequence, designed on the known chemical nucleas e selectivity of this system. The imino NMR spectra are consistent with two distinct families of structure, that is, PORHOE binding either way along t he duplex. 2D spectral, T-2, and linewidth data suggest multiple species wi thin the two conformational families.