Figure 3

Experimental optimization of the automated photo(radio)synthesis of labeled protein. (a) Chemical structures of RhodB-PEG₃-ArN₃ and various DFO-PEG₃-ArN₃ compounds used in model reactions. (b) Photoactivation kinetics indicating the change in DFO-PEG₃-ArN₃ concentration over time measured by peak integration of HPLC chromatograms. (c) A plot of the radiochemical conversion (RCC) versus pH for the synthesis of ⁶⁸GaDFO-PEG₃-azepin-HSA. (d) Radio-ITLC traces (DTPA eluent) of neutralized ⁸⁹Zr-oxalate before (black) and immediately after (blue) the addition of the photoactivatable DFO-PEG₃-ArN₃ chelate indicating rapid complexation. (e) Data on the experimental radiochemical conversion (RCC/%) or photochemical conversion yields (PCY/%) versus protein concentration for model reactions between HSA and RhodB-PEG₃-ArN₃ (pink), pre-labeled ⁶⁸GaDFO-PEG₃-ArN₃ (blue), and simultaneous photoradiolabeling with ⁸⁹Zr-oxalate plus DFO-PEG₃-ArN₃ (black). (f) Representative SEC-HPLC chromatograms of HSA (orange), purified RhodB-PEG₃-azepin-HSA (pink) produced by full automation, and crude reaction mixtures (pre-purification) showing the light-induced formation of ⁶⁸GaDFO-PEG₃-azepin-HSA (blue) and ⁸⁹ZrDFO-PEG₃-azepin-HSA (black) at [HSA] = 15.9 mg mL^-1.