OLIGONUCLEOTIDES WITH NOVEL, CATIONIC BACKBONE SUBSTITUENTS - AMINOETHYLPHOSPHONATES

Oligonucleotide (2-aminoethyl)phosphonates in which the backbone consi sted of isomerically pure, alternating (2-aminoethyl)-phosphonate and phosphodiester linkages have been prepared and characterized. One of t hese single isomer oligonucleotides (Rp) formed a more stable duplex w ith DNA or RNA than its corresponding natural counterpart. Hybrid stab ility was more pH-dependent, but less salt-dependent than a natural du plex. The specificity of hybridization was examined by hybridization o f an oligonucleotide containing one (2-aminoethyl)phosphonate to oligo nucleotides possessing mismatches in the region opposite to the aminoe thyl group. In contrast to oligonucleotides containing (aminomethyl)-p hosphonate linkages, oligonucleotide (2-aminoethyl)phosphonates were c ompletely stable to hydrolysis in aqueous solution. These oligonucleot ides were resistant to nuclease activity but did not induce RNase H me diated cleavage of a complementary RNA strand. Incubation in a serum-c ontaining medium resulted in minimal degradation over 24 hours. Studie s of cell uptake by flow cytometry and confocal microscopy demonstrate d temperature dependent uptake and intracellular localization. (2-Amin oethyl)phosphonates represent a novel approach to the introduction of positive charges into the backbone of oligonucleotides.