Abstract
RNase H is a ubiquitous intracellular enzyme able to selectively hydrolyze the RNA strand of an RNA/DNA hybrid duplex. In the present study, we demonstrate that 5'-boronic acid modified oligonucleotides could inhibit RNase H activity; actvity which could subsequently be restored upon oxidation of the boronic acid moiety. This unprecedented dual property was exploited to engineer a new stimuli-responsive system for the chemoselective imaging of endogenous and exogenous peroxynitrite in RAW264.7 cells.