Figure 4
A. Synthesis of QD conjugate 8 based on a surface-coated carboxylic acid QD 2b. Reagents and conditions: (a) EDC, N-hydroxysuccinimide, PBS, DMSO. B. Synthesis of QD conjugate 9 based on a surface-coated carboxylic acid dendrimer 2b and coupled through a PEG-linker. Reagents and conditions: (a) EDC, N-hydroxysuccinimide, PBS, DMSO; (b) PPh3, THF, H2O; (c) CGS21680 1a, DIEA, PyBOP, DMF. The degree of nucleoside substitution of the QDs was estimated to be equal to 50-100 on conjugate 8 and 30-80 on conjugate 9.