The observation of a hedamycin‐d(CACGTG)2 covalent adduct by electrospray mass spectrometry

Abstract
Covalent binding of the antitumour antibiotic hedamycin to the self-complementary hexadeoxyribonucleotide 5'-CACGTG-3' has been investigated by electrospray ionization mass spectrometry (ESI-MS). Ions due to double-stranded forms of the free 5'-CACGTG-3' and the hedamycin-5'- CACGTG-3' adduct have been observed in ESI mass spectra and their identity has been confirmed by resolution of individual charge states in ESI-MS spectra. Clear evidence that specific base-paired associations are being observed in ESI-MS is provided by the results of a titration experiment involving alkylated and non-alkylated complementary strands. This work demonstrates the potential of this powerful new tool for studying ligand-DNA binding.