LAUSR

Quinone methide precursors 2 and 3 were protected with a photoreactive 2-nitrobenzyl group and conjugated to peptide nucleic acids (PNA) using a Huisgen click reaction. After brief irradiation at 365 nm, crosslinking with com-plementary RNA strands started and was analysed with an ALFexpress sequencer. When using this method, the gel temperature had a major influence on apparent rates. Quinone methides are known to form transient as well as stable bonds with nucleotides. While both were detected at 25 °C, analysis at 57 °C only recorded the stable types of crosslinks suggesting much slower alkylation kinetics. Linker 11 allowed us to attach quinone methides to internal positions of the PNA/RNA duplex and to capture a model of miR-20a with good efficiency.