Taken together, these results suggest that BSA not only enhances catechol browning, as was observed with amino acids and Tris, but also undergoes structural modifications during the process. The narrowing of the primary band at ~66-67 kDa, combined with smearing and the emergence of a faint high-molecular-weight band just above it, likely reflects heterogeneous partial modification of BSA by catechol oxidation products, resulting in a population of adducts.