Chemical studies on the BRET system between the bioluminescence of Cypridina and quantum dots.

We report a bioluminescence resonance energy transfer (BRET) system between Cypridina luciferase (Cluc) and QDs. After coupling of the biotinylated Cluc with streptavidin-QDs, a BRET emission of QDs through the resonance energy transfer from the oxidation of Vargula (Cypridina) luciferin was observed. A luciferin analogue having a naphtyl group at C6-position showed a large blue shift of the emission spectrum, which improved the ratio of this BRET system. After directly conjugating the luciferase with QDs, an efficient BRET was observed similar to the previous BRET using organic dyes. Furthermore, the symmetric emission spectra of QDs show a potential to realize multiplexed imaging based on the BRET of Cluc using the same luciferin.