Interaction between fluorescence-labeled fibronectin fragments studied by gel high-performance liquid chromatography.

Fibronectin is a large, adhesive glycoprotein which self-associates on many cell surfaces. We have begun to study this reaction by determining the domains of fibronectin which interact with each other. To avoid possible solid-phase artifacts of affinity chromatography, we have devised a solution-phase assay in which the smallest fibronectin fragment is labeled with fluorescamine, mixed with unlabeled fibronectin, and complexation is observed by the appearance of a new higher-molecular-weight peak on gel high-performance liquid chromatography columns. The assay allowed use of excess unlabeled reactant, high-sensitivity, low background without removal of reagent, and fast analysis. Our results show that the amino- and carboxyl-terminal fibronectin fragments bind the native molecule in solution.