As substitutes for antisense and tripler oligonucleotides, oligopeptides containing N-beta-(thymin-1-ylacetyl) beta-aminoalanine and N-beta-(cytosin-1-ylacetyl) beta-aminoalanine moieties were synthesized on solid support by using standard Boc-chemistry. The obtained peptide containing ten thymine bases was shown to form a hybrid duplex with a complementary oligo DNA, dA(10), with a melting temperature (Tm) of 36.5 degrees C at pH 7.0. (C) 1997 Elsevier Science Ltd. All rights reserved.