Characterization of the QD-luc8 conjugates by dynamic light scattering (a, b), TEM (c, d), spectroscopic analysis (e, f), and electrophoresis (g). Encapsulated QD-BRET conjugates (b, d) are larger than unmodified conjugates (a, c) due to polymeric encapsulation as well as cross-linking of the conjugates, and retain both bioluminescence (e, f) and fluorescence emissions. Dashed lines in e and f represent the spectra of unmodified QD-BRET probes, and solid lines in e and f represent fluorescence of encapsulated QD-BRET conjugates.