Fig. 12. Copper-free click chemistry for protein conformational change study. (A) Schematic illustration of double-site specific labelling strategy with click chemistry. (B) Fluorescence scanning images of SDS-PAGE result of CaM labeled with BODIPY-TMR-X (10) or/and BODIPY-FL (9) via iEDDA reaction. (C) FRET signal changes between 10 and 9 according to concentrations of urea. (D) Relative donor fluorescence changes according to concentrations of Ca²⁺. Reproduced from ref. 63 with permission from Springer Nature, copyright 2014.