Hybridization dependent cleavage of internally modified disulfide–peptide nucleic acids

Selectivity of the cleavage of single stranded over hybridized forms of internally modified disulfide–peptide nucleic acids (PNA) has been optimized using a series of phosphines and thiols, which have different sizes and charges. For the most selective cleaver found (tris-(carboxyethyl)-phosphine), reactivity of single stranded PNA is 33 times higher than that of the PNA–DNA duplex. Selectivity of single stranded disulfide–PNA cleavage has been explained in terms of electrostatic interaction between the substrate and the cleaver.