The isolation of large molecular mass procyanidins from grain sorghum and their interaction with [14C]methyl bovine serum albumins.

1. Three protein-free procyanidin fractions with molecular masses of 4000, 8000 and 10,000-50,000 were isolated from a bird resistant sorghum grain. 2. The interaction between the largest procyanidin and 88 or 1% methylated bovine serum albumin (14C labelled) is stronger with the more methylated protein over a range of 0-2.75 ionic strength at pH 5. This indicates the involvement of apolar forces throughout the range though apolar forces were more pronounced from 0.7-2.75 ionic strength. 3. In the interaction between procyanidins of different molecular masses and 88% 14C-methylated bovine serum albumin the smaller procyanidins exhibited a more pronounced sigmoidal precipitation pattern than the larger with an increase in their concentrations.