Figure 3

In vivo FRET. A) CFP, YFP and sensitized emission (FRET) images (Left panel) and emission spectra (Right panel) were collected from skin cells expressing Ycam. The red and blue spectrum are pre- and post-YFP photo destruction respectively. Note the gain in CFP fluorescence after photo destruction of YFP. B) Control experiments for intravital FRET imaging. (Left panel) The collected FRET images in A were corrected as described in methods. FRET was not observed in cells expressing only CFP or YFP, consistent with proper correction. (Right panel) The emission spectrum acquired using CFP excitation wavelength (405 nm) of a cell expressing only YFP. The expression level of YFP is similar to that of Ycam in A. Note that YFP is inefficiently excited at 405 nm, and that photo destruction of YFP does not result in an increase of fluorescence at CFP wavelengths.