Rigid peptide backbones and backbone-to-side chain H-bonds permit the design of α-nucleopeptides with known 3D-structure; thymineâthymine base pairing is also observed.
Three thymine-based nucleo-heptapeptides, each containing two nucleo-amino acids and zero, one or four Aib residues, respectively, have been synthesized. A single Aib residue is enough to promote the adoption of a helical structure in our nucleopeptides and to increase significantly their resistance towards enzymatic degradation. The insertion of four Aib residues, out of seven residues in the sequence, affords a rigid, 310-helical nucleopeptide that is substantially unaffected by serum enzymes and is not cytotoxic.