Fig. 1. Clickable drug surrogates for imaging of PARP1 protein in vitro. (A) Copper-free click reaction between AZD2281-TCO and Texas Red-Tz in MDA-MB436 cells. (B) Immunofluorescence staining of PARP1 protein with green fluorescent monoclonal anti-PARP antibody. (C) A composite overlay on phase contrast. (D) Increase in the ratio of nuclear/cytoplasmic fluorescence signal for AZD2291-TCO/Texas Red-Tz without (circle) and with (square) the blocking reagent AZD2281. Scale bar: 20 μm. Reproduced from ref. 35 with permission from John Wiley and Sons, copyright 2010.