Fig. 2. S-FR4-Fc and S-FR1-Fc bind to FGF in vitro. Heparin acrylic beads were first soaked with FGF2 (2) or FGF8 (8) and then incubated with 300 µl of cell supernatant from DF-1 cells infected with the S-FR4-Fc or S-FR1-Fc constructs. Control beads (He) were incubated with 2% BSA prior to exposure to the cell supernatants. Proteins adsorbed on these beads were separated by SDS-Page and blotted onto a membrane; they were recognized using an anti-human Fc fragment antibody. Both S-FR4-Fc and S-FR1-Fc bind to FGF2- and FGF8-loaded beads, but not heparin beads.