Photophysical characterization of oligopyrene modules for DNA-based nanosystems

Abstract

The photophysics of free pyrenedicarboxamide (Py-DCA) in solution as well as of single-stranded and double-stranded oligonucleotides (ss and ds ONs) containing 1–7 pyrene building blocks per strand were studied by steady-state and time-resolved fluorescence spectroscopy. It was found that the fluorescence quantum yield Φ_F of free Py-DCA chromophore in solution is rather high (Φ_F = 0.44). However, after incorporation of the chromophore into a ss ON the monomeric chromophore fluorescence is quenched more than 40-fold due to electron-transfer reactions with ON bases. An increase of the number n of neighboring pyrenes in an ON results in Φ_F growth up to 0.25 at n = 6. Starting from n = 2, all fluorescence belongs mainly to excimer formed by pyrene chromophores. Sections composed of multiple pyrenes may be considered as robust functional entities that may serve as independent modules in DNA-based, functional nano-architectures.