| abstract |
Oligonucleotides having tandem sequences of inverted polarity, i.e., oligonucleotides comprising regions of the formula: ##STR1## wherein --C-- symbolizes any method of coupling the nucleotide sequence of opposite polarity, n are useful for forming an extended triple helix with a double-helical nucleotide duplex. The inverted polarity also stabilizes the single-strand oligonucleotides to exonuclease degradation. |