DNA binding of a molecular-scale receptor in the presence of zinc(II) ions

The properties of a tritopic artificial biological probe are described. This probe consists of a luminescent pyrene-thiophene unit connected by an ethynylene group to a 2,2':6',2 '' terpyridine (terpy) cation binding site. The pyrene unit, as evidenced by fluorescence spectroscopy under illumination at 400 nm, is capable of intercalating into double-stranded calf-thymus DNA in H2O (buffered, pH = 7.0) at 25 degrees C. The binding constant K was calculated to be 6.0x10(5)m(-1). Ti-tration of zinc(II) ions in an aqueous (pH = 7.0) solution containing the intercalated probe results in fluorescence quenching which again is a consequence of the zinc(II) ions binding to the terpy site. The DNA-bound probe has also been shown to undergo singlet energy transfer to intercalated ethidium bromide with a rate constant of 9.4 x 10(9) s(-1). ((c) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2005).