5-Amino-dU: a nucleoside analogue in the central strand of DNA triplex for orientation selective binding of A/G/C/T in the third strand.

[formula: see text] 5-Amino-dU, a designed nucleoside analogue, when placed in the central strand of DNA triple helix, recognizes all four bases A, G, C, and T in the third strand, with a selectivity based on the orientation (parallel/antiparallel) of the third strand.