Fig. 2. Average cluster size for 5-integrin in CHO B2 cells. Confocal images of a CHO K1 cell expressing GAP-GFP and plated on coverslips coated with 2 µg ml^–1 fibronectin (A), or CHO B2 cells expressing 5-GFP plated on coverslips coated with either 200 µg ml^–1 poly-D-lysine (B) or 2 µg ml^–1 fibronectin (C). Data were corrected for the fact that the EGFP is 1.4 times brighter than the GAP-GFP (S65A). The plot shown is the average number of integrins per cluster calculated from many regions on many cells (D), 166 areas, 44 cells for GAP-GFP, 102 areas, 18 cells for 5-GFP on poly-D-lysine, and 137 areas, 30 cells for 5-GFP on fibronectin. The DA values were calculated from the spatial correlation function x-axis fit because the GAP-GFP was moving during the time the laser beam moved from one row of the image to the next. For consistency the integrin DA values were also calculated from the x-axis fit. The DA of 6.02±0.07 for GAP-GFP was used to normalize the data and calculate the number of proteins per cluster for 5-integrin. The break for low and high expressers was set at an average intensity of below or above 300 intensity units. Error bars are s.e.m. Scale bars, 5 µm.