Molecular beacons have been used extensively for the detection of nucleic acids and are suitable for analyses in vivo. Recently, hospitalization of hundreds of people in the developing world has resulted from a waterborne viral infection known as the Coxsackievirus B6 (CVB6). A new molecular beacon has been proposed by Yeh et al. and uses a quantum dot - gold nanoparticle based FRET system to signal hybridisation of the molecular beacon to a CVB6 specific nucleic acid sequence. Yeh, H-S.; Yates, M.V.; Mulchandani, A.; Chen, W. Chem. Comm. 2010, 46, 3914-3916.

Using the reported FRET efficiency and a Förster distance of 4 nm, determine the average separation distance between the quantum dot and an adjacent gold nanoparticle for the molecular beacon (in the absence of the target sequence).