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. Author manuscript; available in PMC: 2011 Dec 1.
Published in final edited form as: Curr Opin Chem Biol. 2010 Oct 15;14(6):803–809. doi: 10.1016/j.cbpa.2010.09.015

Figure 4.

Figure 4

(left) Surface labeling of human tumor cells with a malachite green (MG) fluorogen-activating protein (FAP). Stably transformed M21 melanoma cells expressing fluorogen-activating protein HL4-MG fused to platelet-derived growth factor receptor (PDGFR) were imaged as a confocal stack at 488-nm excitation using 10 nM impermeant malachite green derivative MG-11p [18••]. Photomicrograph is a three-dimensional reconstruction of the stack. (center) Surface labeling of fibroblasts with a thiazole orange (TO1) FAP. Stably transformed NIH3T3 cells expressing fluorogen-activating protein HL1.1-TO1 fused to PDGFR and imaged using 40 nM impermeant thiazole orange derivative TO1-2p. (right) Simultaneous surface labeling of fibroblasts with MG and TO1 FAPs. NIH3T3 cells respectively expressing the FAPs of left and center panels were mixed 1:1 and imaged using 10 nM MG-2p and 40 nM TO1-2p. The transparency of surface-labeled cells allows fine discrimination of contact surfaces between cells of different colors. Scale bars, 10 µm. Adapted by permission from Macmillan Publishers Ltd: Nature Biotechnology Vol 26 Issue 2, pp 235–240 (2008), copyright 2007.