a) HHRz secondary structure with crosslinked nucleobases in yellow. b) Cleavage products produced by alkali hydrolysis of the Pt-crosslinked HHRzES-SS(dC17, C1.1ps) complex formed using 5′ end-labeled HHRzES. Control lanes (blue overline): C: 5′ endlabeled HHRzES T1: G-specific sequence ladder generated by partial nuclease digestion with RNase T1 -OH: Reference alkali hydrolysis ladder. Platinum crosslinked lanes (red overline): C: isolated, Ptcrosslinked HHRz-SS(dC17, C1.1ps) –OH lanes: isolated, Ptcrosslinked HHRz-SS(dC17, C1.1ps) treated using alkali hydrolysis conditions for increasing amounts of time. Yellow arrows designate platinum crosslinking sites as indicated by loss of hydrolysis products 3′ to the site.