Dodecin from Halobacterium salinarum is a dodecameric, hollow-spherical protein, which unspecifically adopts flavin molecules. Reduction of flavin dodecin holocomplexes induces dissociation into apododecin and free flavin. Unspecific binding and dissociation upon reduction were used as key properties to construct an electrochemically switchable surface, which was able to bind and release dodecin apoprotein depending on the applied potential. A flavin modified electrode surface ͑electrode-DNA-flavin͒ was generated by direct adsorption of double stranded DNA ͑ds-DNA͒ equipped with flavin and disulfide modifications at opposite ends. While the disulfide functionality enabled anchoring the ds-DNA at the gold surface, the flavin exposed at the surface served as the redox-active dodecin docking site. The structures of protein and flavin-DNA hybrid ligands were optimized and characterized by x-ray structural analysis of the holocomplexes. By surface plasmon resonance ͑SPR͒ spectroscopy, the adsorption of flavin modified DNA as well as the binding and the electrochemically induced release of dodecin apoprotein could be shown. When the surface immobilization protocol was changed from direct immobilization of the modified ds-DNA to a protocol, which included the hybridization of flavin and thiol modified DNA at the surface, the resulting monolayer was electrochemically inactive. A possible explanation for the strong influence of the surface immobilization protocol on addressing dodecin by the applied potential is that electron transfer is rather mediated by defects in the monolayer than modified ds-DNA.

Learning from nature: In nature, riboflavin binding proteins are responsible for the transport and release of riboflavin. Here, the development of a molecular photorelease system based on the riboflavin binding protein dodecin is presented. Any drug or active chemical linked to a flavin can be captured by dodecin and transported to a location of interest. Irradiation with blue light results in the release of the ligands.magnified image

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