We have designed a 21-residue alpha-peptide that simultaneously recognizes two decadeoxyoligothymidine (dT(10)) tracts to form triplexes with a peptide DNA strand ratio of 1:2. The synthetic peptide side chain displays 10 melamine rings, which provide a bifacial thymine-recognition interface along the length of the 21-residue peptide. Recognition is selective for thymine over other nucleobases and drives the formation of ternary peptide center dot[dT(10)](2) complexes as well as heterodimeric peptide center dot[dT(10)C(10)T(10)] hairpin structures with triplex stems.