Spectroscopic studies of poly(N‐acyldehydroalanines) containing asymmetric nucleic acid base derivatives as pendant groups

Water‐soluble polynucleotide analogs having a poly(N‐acyldehydroalanine) {poly(α[–(N‐acylamino)acrylate])} backbone were studied by 360‐HMz1H‐NMR, UV, and CD spectroscopies. Significant UV hypochromicity values for the polymers versus monomer model compounds as well as peak shifts in the NMR spectra implied a high degree of base stacking in these systems. The CD spectrum of poly{(‐)‐2‐[2‐(thymin‐l‐yl) propanoamido] propenoic acid} (p(‐)TDHA), having an optically active side chain, was remarkably insensitive to the degree of neutralization of the polymer, but was very sensitive to the ionic strength of the solution. Continuous variation mixing experiments revealed no base‐pairing interactions between complementary charged polymers, and weak interactions between charged and uncharged polymers and model compounds. These results suggest that the polymers are conformationally restricted in solution.