Guanosine assemblies: newly used matrices for chiroptical studies on biliverdin

Abstract

Guanine derivatives and biliverdin (BV) are biologically important units. As BV racemises in solution, we utilised various guanine assemblies as suitable sensitive matrices for the enantioselective recognition of BV in circular dichroism (CD) studies. Using electronic CD, we separately detected the interacting P form of BV (visible) and its effect on guanosine (Guo) assemblies (UV). The interaction of the P form was confirmed by vibrational CD even though the signals of Guo and BV overlapped. BV preferred the monomers and vertical stacks ((M)n) of guanosine 5′-monophosphate (GMP) as interacting partners. BV–GMP interaction was also observed in the case of vertically assembled GMP quartets ((G4)n), but this interaction was shown to be destructive for (G4)n. To stabilise (G4)n assemblies more intensively and to protect them against disruption by BV, we applied Guo. BV reorganised the Guo/GMP supramolecular structure although it had demonstrated high stability in our previous study.