Polymerization of acid-solubilized fibrin monomer was measured by monitoring A350 nm. The normal and Marburg acid-solubilized des-AB fibrin monomers were prepared as described in Materials and Methods. The reaction was started by dilution of 18.4 μL of fibrin monomer (20 μg) with 500 μL of 25 mmol/L imidazole-buffered saline, pH 7.4, and aggregation was monitored by A350.