The binding of AT to heparin was analyzed by protein fluorescence enhancement.41 rhAT (○) and phAT (□) were diluted to 20 nmol/L in 20 mmol/L sodium phosphate, 100 mmol/L NaCl, 100 μmol/L EDTA, 0.1% PEG, and pH 7.4. Heparin was added in 1-μL aliquots, and fluorescence was measured with excitation at 280 nm and emission at 340 nm.