Fig. 7. FRET for FAK together with either paxillin or CAS. NIH 3T3 cells were transfected with cDNA encoding pairs of CFP- and YFP-fusion proteins as indicated. (A) Images are displayed in spectral scale for the CFP and YFP fusion proteins, for their fluorescence ratio, and for the calculated FRET between the co-expressed molecules. CFP-paxillin/YFP-FAK (pax-FAK) and CFP-FAK/YFP-CAS (FAK-CAS) pairs display relatively high FRET values. (B) FRET of indicated donor/acceptor pairs in focal complexes. First image displays the localization of the acceptor in inverted grey levels (C) Quantitative FRET analysis of the indicated pairs. The data are presented as mean ± s.e. of FI in focal adhesions measured in 8 to 15 cells. Bar, 2 µm.