Binding characteristics of dopa (3,4-dihydroxyphenylalanine) and its metabolites to bovine serum albumin as measured by ultrafiltration technique.

The interaction between 3,4-dihydroxyphenylalanine (DOPA), dopamine, 3-methoxytyramine and homovanillic acid and bovine serum albumin (BSA) was investigated by the ultrafiltration technique. The apparent binding constants were determined assuming the equivalence and independence of the binding sites on the BSA molecule. The binding constants were in the range of log K = 2.85 to 3.77 with 1 to 2 binding sites. The affinity of ligands to BSA strengthened with progression of the metabolism in the order of DOPA less than dopamine less than 3-methoxytyramine less than homovanillic acid.