Nichtnucleosidische Chromophore im Stamm eines molekularen Leuchtfeuers („molecular beacon“) hemmen die Excimerfluoreszenz durch die Bildung eines Donor‐Akzeptor‐Komplexes (siehe Bild). Die ausgezeichnete Verringerung der Hintergrundfluoreszenz ermöglicht es, eine Ziel‐DNA oder ‐RNA in Gegenwart eines deutlichen Überschusses der Sonde nachzuweisen.

A light-harvesting system based on a DNA-organized oligopyrene-cyanine complex is described. Energy transfer from the pyrene units to the cyanine dye was found to proceed via FRET from locally confined excimers to the acceptor.

The DNA three-way junction serves as a scaffold for the molecular organization of non-nucleosidic alkynylpyrene and perylenediimide chromophores located at the branch point of the structure. Depending on the composition of the tripartite assembly, the constructs possess distinct spectroscopic properties, ranging from monomer or excimer fluorescence to completely quenched tripartite aggregates.

Pyrene excimer fluorescence is efficiently regulated through formation of π-stacked aggregates between dialkynylpyrene (Y) and perylenediimide (E) residues located in the stem region of a molecular beacon (MB). The building blocks form organized, multichromophoric complexes in the native form. Hybridization to the target results in a conformational reorganization of the chromophores. The nature of the aggregates was investigated by changing the number of chromophores and natural base pairs in the beacon stem. The formation of different types of complexes (EYEY→YEY→EY) is revealed by characteristic spectroscopic changes. The data show that signal control is an intrinsic property of the interacting chromophores. The directed assembly of non-nucleosidic chromophores can be used for the generation of an on/off switch of a fluorescence signal. The concept may find applications in various types of light-based input/output systems.

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