Interactions of the human telomeric DNA with terbium–amino acid complexes

The human telomeric DNA can form four-stranded structures: the G-rich strand adopts a G-quadruplex conformation stabilized by G-quartets and the C-rich strand may fold into an I-motif based on intercalated C · C+ base pairs. There is intense interests in the design and synthesis of compounds which can target telomeric DNA and inhibit the telomerase activity. Here we report the thermodynamic studies of the two newly synthesized terbium–amino acid complexes bound to the human telomeric G-quadruplex and I-motif DNA which were studied by means of UV–Visible, DNA meltings, fluorescence and circular dichroism. These two complexes can bind to the human telomeric DNA and have shown different features on DNA stability, binding stoichiometry, and sequence-dependent fluorescence enhancement. To our knowledge, this is the first report to show terbium–amino acid complexes can interact with the human telomeric DNA.