Thermal aggregation of beta-lactoglobulin in presence of metal ions.

In this work, we report a study of the effects of zinc and copper ions on the heat-induced aggregation of beta-lactoglobulin (BLG). Kinetics investigations on aggregates growth by light scattering measurements and on secondary structure changes by FTIR absorption measurements show the different role played by the two metals during the whole process. In particular, the presence of zinc in solution promotes the formation of aggregates of BLG at a lower temperature than copper. Then, at fixed temperature, formation of a large amount of aggregates, of large dimension, is observed for Zn-BLG in shorter time; on the contrary, the presence of copper in solution does not affect the aggregation process while the secondary structure changes and the formation of different stronger intermolecular H-bonds, which probably lead to build a network of bonds that takes towards gelation. Our studies show how time evolution of aggregation process of BLG is dramatically affected by the presence of metal ions in solution and structural protein modifications are induced by different divalent metal ions.