Helical self-assembled chromophore clusters based on DNA-like architecture

DNA duplexes were functionalized covalently by clusters of five adjacent chromophores consisting of 5-(pyren-1-yl)-2′-deoxyuridine (Py-U) and 5-(10-methyl-phenothiazin-3-yl)-2′-deoxyuridine (Pz-U). The chromophores form a regular helical π-array along the major groove of duplex DNA when the 5-fold chromophore-modified oligonucleotides are hybridized with an unmodified counter strand. As a result, these chromophores interact significantly and their fluorescence and absorption properties can be modulated by the sequence within the π-array. The 5-fold Py-U stack shows a strongly enhanced emission. The presence of intervening Pz-U groups quenches the fluorescence of the Py-U chromophores. Such modulation of the optical properties within a chromophore stack is potentially useful for optical nanodevices and as nucleic acid sensors for molecular diagnostics. The duplex architecture of DNA is suitable to provide the supramolecular structural scaffold for a directed arrangement of chromophores.