Analytical pyrolysis to gain insights into the protein structure. The case of ovalbumin

We report a novel study based on analytical pyrolysis coupled with mass spectrometry to investigate, at the molecular level, the formation of aggregates and cross-linked structures in ovalbumin (OVA). For this scope, OVA was dissolved in water at different concentrations and temperatures (up to 80 °C), and was added with 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride (EDC). The formation of β-sheets and intermolecular aggregates, which are stabilized by weak hydrophobic and hydrogen bonds, is favoured in OVA by higher protein concentration and temperatures. The cross-linker (EDC) gives the formation of covalent bonds randomly distributed in the protein, inducing significant portions of random coil structures in OVA. FTIR-ATR spectroscopy was employed to study the protein conformation. Evolved gas analysis coupled with mass spectrometry (EGA-MS) and pyrolysis coupled with gas chromatography mass spectrometry (Py-GC–MS) were used to characterise the gaseous compounds evolved during pyrolysis at the different temperatures. Aggregation and cross-linking increase the thermal stability of OVA and significantly affect its pyrolytic profile. The study reveals that analytical pyrolysis coupled to mass spectrometry can be used to gain insights into the protein structure.