[A study of ligand binding to protein using resonance energy transfer from the isoindole fluorescent label to ligand]

A method for studing the binging of ligands absorbing the light in the region of 350-550 nm to protein is described. The method is based on resonance energy transfer between the fluorescent label covalently bound to the protein and the ligand. The isoindole label, a product of the reaction of the protein with o-phthalaldehyde in the presence of 2-mercaptoethanol, was used as a fluorescent donor. The method was used to determine the binding parameters of a fluorescent probe (a naphthalimide derivative) with human serum albumin. A comparison of the results obtained by the resonance energy and transfer by equilibrium dialysis showed a high accuracy of the resonance energy transfer method.