Schematic of single wavelength protein sensor mechanisms. (a) EOS protein constructs are bound to biotin (B) and incubated with streptavidin (SA) coated cells to label the cell surface with sensor. Adapted with permission from S. Namiki, H. Sakamoto, S. Iinuma, M. Iino, and K. Hirose, Eur. J. Neurosci. 25, 2249 (2007). Copyright 2007, Wiley. (b) iGluSnFR constructs made up of cGFP (disk) inserted into GltI typically have disrupted cGFP structures with dim fluorescence. The conformation change in GltI caused by glutamate binding structurally realigns cGFP to elicit brighter fluorescence. Reprinted with permission from J. S. Marvin et al., Nat. Methods 10, 162 (2013). Copyright 2013, Nature Publishing.