Increased DNA binding and sequence discrimination of PNA oligomers containing 2,6-diaminopurine

Abstract
The synthesis of a diaminopurine PNA monomer, N -[ N6 -(benzyloxycarbonyl)-2,6-diaminopurine-9-yl] acetyl- N -(2-t-butyloxycarbonylaminoethyl)glycine, and the incorporation of this monomer into PNA oligomers are described. Substitution of adenine by diaminopurine in PNA oligomers increased the Tm of duplexes formed with complementary DNA, RNA or PNA by 2.5–6.5°C per diaminopurine. Furthermore, discrimination against mismatches facing the diaminopurine in the hybridizing oligomer is improved. Finally, a homopurine decamer PNA containing six diaminopurines is shown to form a (gel shift) stable strand displacement complex with a target in a 246 bp double-stranded DNA fragment.