FLUOROSPECTROMETRIC ANALYSIS OF HEPARIN INTERACTION WITH FIBROBLAST GROWTH-FACTORS

The fluorescence emission of a single tryptophan residue present in bo th FGF-1 and FGF-2 was used as a structural probe to directly assess t he interaction of the growth factors with heparin or beta-cyclodextran tetradecasulfate. About 20-25% of the fluorescence of either FGF-1 or FGF-2 is quenchable, and is dependent on sulfation of the ligands. Th e quenchable fluorescence is associated with about 20% of total FGF, s uggesting the presence of two fluorospectrometric forms of the protein . The equilibrium dissociation constants, deter mined by this method, for heparin or beta-cyclodextrin tetradecasulfate binding to FGF-1 are about 1 nM, whereas the values for FGF-2 are 1 and 23 nM, respectivel y. The method provides a direct tool to evaluate FGF-ligand interactio n and assess the structural integrity of the proteins.