Photo-Tethers for the (Multi-)Cyclic, Conformational Caging of Long Oligonucleotides.

Intramolecular circularization of DNA oligonucleotides was accomplished by incorporation of alkyne-modified photolabile nucleosides into DNA sequences, followed by a CuI -catalyzed alkyne-azide cycloaddition with bis-azido linker molecules. We determined a range of ring sizes, in which the caged circular oligonucleotides exhibit superior duplex destabilizing properties. Specific binding of a full-length 90 nt C10 aptamer recognizing human Burkitt's lymphoma cells was then temporarily inhibited by locking the aptamer in a bicircularized structure. Irradiation restored the native aptamer conformation resulting in efficient cell binding and uptake. The photo-tether strategy presented here provides a robust and versatile tool for the light-activation of longer functional oligonucleotides, noteworthy without prior knowledge on the structure and the importance of specific nucleotides within a DNA aptamer.