Synergistic stabilization of nucleic acid assembly by oligo-N3'-->P5' phosphoramidate modification and additions of comb-type cationic copolymers.

Synergic stabilization of DNA triplexes by oligo-N3'-->P5' phosphoramidate (PN) modification and additions of comb-type cationic copolymers was demonstrated. The combination of the copolymer and the PN modification increased triplex K(a) about 4 orders of magnitude. Kinetic analysis revealed that observed stabilization resulted from kinetic complimentarity between increased association rates by the copolymer and decreased dissociation rates by the PN modification of triplex forming oligonucleotides. No countering interference between these stabilizing effects was observed. We propose that kinetic analyses of stabilizing effects permit selection of a rational combination of stabilizing methods for successful synergy in stabilizing complex formation.