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

• Trypsin inhibitor (TI) binds HSA and BSA via hydrophilic and hydrophobic contacts.
• BSA forms more stable complexes than HSA.
• Trypsin inhibitor complexation alters protein secondary structure.
• TEM shows serum protein aggregation and fibrillation upon TI interaction.

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) × 104 M−1 and KTI-BSA = 1.1 (±0.4) × 106 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.

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