... linker containing a calmodulin domain and a calmodulin ligandpeptide called M13.When Ca2+ is present, it binds to the calmodulin domain, inducing a con‐formational change and binding of the proximal ... sequence. The M13 bindingresults in shortening of the linker, bringing CFP within FRET distance of YFP and changingthe emission wavelength from cyan to yellow. The Ca2+ binding affinity was found ... the insertions of antigen-bindingloops from antibodies raised against streptavidin-phycoerythrin, biotin-phycoerythrin,TrkB, or GADPH, all while maintaining 40% of the fluorescence and 60% of...