Triple helix formation by oligonucleotides on DNA extended to the physiological pH range

We report here that oligodeoxyribonucleotides which contain 5-bromouracil (Br^5U) and 5-methylcytosine (m^5C) bind duplex DNA at the same homopurine target sequence as their T/C analogues but with greater affinities and over an extended pH range. Oligonucleotides containing uracil (U) bind with lower affinity (Figure 1)