Synthesis and Avidin Binding of Ruthenium Complexes Functionalized with a Light-Cleavable Free Biotin Moiety.

ABSTRACT: In this work the synthesis, photochemistry, and streptavidin interaction of new [Ru(tpy)(bpy)(SRR')](PF₆)₂ complexes where the R' group contains a free biotin ligand, are described. Two different ligands SRR' were investigated: An asymmetric ligand 1 where the Ru-bound thioether is a N-acetylmethionine moiety linked to the free biotin fragment via a triethylene glycol spacer and a symmetrical ligand 2 containing two identical biotin moieties. The coordination of these two ligands to the precursor [Ru(tpy)(bpy)Cl]Cl was studied in water at 80 °C. In such conditions the coordination of the asymmetric ligand 1 occurred under thermodynamic control. After the reaction, a mononuclear and a binuclear complex were isolated. In the mononuclear complex, the ratio of methionine- {[6](PF₆)₂} vs. biotin-bound {[7](PF₆)₂} regioisomer was 5.3 and the free biotin fragment of [6](PF₆)₂ allowed to purify it from its isomer [7](PF₆)₂ at small scales using avidin affinity chromatography. Coordination of the symmetrical ligand 2 afforded [Ru(tpy)(bpy)(2)](PF₆)₂ {[8](PF₆)₂} in synthetically useful scales (100 mg), good yield (82?%), and without traces of the binuclear impurity. In this complex, one of the biotin remains free whereas the second one is coordinated to ruthenium. Photochemical release of ligand 2 from [8](PF₆)₂ occurred upon blue light irradiation (465 nm) with a photosubstitution quantum yield of 0.011 that was independent of the binding of streptavidin to the free biotin ligand.

SUBMITTER: Siewert B 

PROVIDER: S-EPMC6473509 | biostudies-literature | 2018 Oct

REPOSITORIES: biostudies-literature