Spectroscopic examination of linear poly(ethylenimine) containing nucleic acid pendants as polynucleotide analogs

The NMR spectra and UV absorptions of polynucleotide analogs with a poly(ethylenimine) (PEI) backbone containing adenine, cytosine, and hypoxanthine pendants have been examined. As has been shown in single‐stranded polynucleotides, these polymers also exhibited base stacking behavior in aqueous solution as well as in 2,2,2‐trifluoroethanol. Such stacking resulted in significant UV hypochromicities and observed differences in the NMR spectra compared to the corresponding model compounds. From continuous variation mixing experiments, well‐defined base pairing interactions were observed between complementary graft polymers in aqueous solutions. Enhanced UV hypochromicity due to such interactions was also observed.