Synthesis, incorporation efficiency, and stability of disulfide bridged functional groups at RNA 5′-ends

Modified guanosine monophosphates have been employed to introduce various functional groups onto RNA 5'-ends. Applications of modified RNA 5'-ends include the generation of functionalized RNA libraries for in vitro selection of catalytic RNAs, the attachment of photoaffinity-tags for mapping RNA-protein interactions or active sites in catalytic RNAs, or the nonradioactive labeling of RNA molecules with fluorescent groups. While in these and in similar applications a stable linkage is desired, in selection experiments for generating novel catalytic RNAs it is often advantageous that a functional group is introduced reversibly. Here we give a quantitative comparison of the different strategies that can be applied to reversibly attach functional groups via disulfide bonds to RNA 5'-ends. We report the preparation of functional groups with disulfide linkages, their incorporation efficiency into an RNA library, and their stability under various conditions.