A) Schematic diagram of the FRET interaction between a QD and a GFP-like fluorescent protein. (B) FRET results using tdTomato fluorescent protein as acceptor with 520 nm emitting QD donors; N being the average number of proteins per QD-conjugate. (C) Quenching efficiency derived from the PL integrated intensities for QDs mixed with His-appended proteins (brown squares). The data for the His-free proteins and His10-only (no fluorescent protein) controls are also shown (blue diamonds and red squares). Figure reprinted from ref. 88, with permission of the American Chemical Society, and kindly provided by G. Bao.