Trypsin inhibitor complexes with human and bovine serum albumins: TEM and spectroscopic analysis

We report the binding of trypsin inhibitor (TI) with human serum albumin (HSA) and bovine serum albumin (BSA) at physiological conditions, using FTIR, CD, UV-Visible spectroscopic methods and transmission electron microscopy (TEM). Structural analysis showed that trypsin inhibitor binds HSA and BSA via hydrophilic and hydrophobic contacts with overall binding constants of KTI-HSA=1.4 (±0.5)×10(4)M(-1) and KTI-BSA=1.1 (±0.4)×10(6)M(-1). Trypsin inhibitor complexation induces minor reduction of the protein α-helix and a major increase in β-sheet structure. TEM images show that trypsin inhibitor complex formation leads to the protein aggregation and fibrillation.