By conjugating pyrrole (Py)/imidazole (Im) hairpin polyamides with CBI, a stable alkylating moiety, we have developed a new type of DNA-sequence-specific alkylating agent. The sequence specificity and alkylation efficiency of the CBI conjugates were analyzed with high-resolution denaturing gel electrophoresis using linear 450- and 1000-bp DNA. The results demonstrate that CBI conjugates selectively alkylate adenine in specific sequences, whereas the previous type of alkylating polyamide, which contains segment A of DU-86, alkylates both adenine and guanine.