Light Regulation of Aptamer Activity:  An Anti-Thrombin Aptamer with Caged Thymidine Nucleobases

“Caged” derivatives of a 15 nucleotide ssDNA anti-thrombin aptamer have been synthesized in which thymidine nucleotides are modified with photolabile protecting groups. One caged thymidine in a key location is enough to completely mask the aptamer's function in respect to their affinity for thrombin and their inhibition of the blood clotting cascade. With light (366 nm) the caging group can be removed, yielding the unmodified active aptamer.