Preparation of 1-ethynylpyrene-modified DNA via Sonogashira-type solid-phase couplings and characterization of the fluorescence properties for electron-transfer studies

A range of 1-ethynylpyrene-modified oligonucleotides (Py-drop-dU) has been prepared by a special semi-automated strategy using Sonogashira-type cross-coupling conditions in the solid phase. The absorption and fluorescence properties of the Py-drop-dU-modified single strands and their corresponding double-stranded duplexes have been characterized. The presented spectra show that the Py-drop-dU emission is quenched in DNA duplexes bearing a thymine or cytosine adjacent to the Py-drop-dU group. This shows that the Py-drop-dU moiety is able to inject an electron into the base stack while simultaneously acting as a spectroscopic label to enable the observation of these processes. Hence, Py-drop-dU-modified oligonucleotides are promising donor systems in order to study electron injection and electron transport in DNA spectroscopically. I ((C) Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003).