Incorporating charged amino-acid side chains in polypeptides polymer backbone to improve solubility， usually leads to reduced secondary structuring. Here we show that highly water-soluble (>15 mg.mL-1)， β-sheets structured， ionic polypeptide polymers can be obtained via nucleotide monophosphate grafting onto simple poly(γ-propargyl-L-glutamate) backbone. This synthetic methodology has been applied to the synthesis of thymidine-based nucleopolypeptide presenting stable β-sheets conformation in aqueous solutions with pH values comprised between 4 and 8. These polymeric analogues of nucleoproteins exhibited selective interaction with simple DNA sequences displaying adenine.