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<p>Structural modifications in bovine serum albumin (BSA) may alter its ability to act as a carrier for hydrophobic bioactive compounds such as astaxanthin (AST). This study investigated how thermal denaturation (BSA<sub><i>den</i></sub>) and ultrasonic treatment (BSA<sub><i>US</i></sub>) affect the conformation of BSA and its interactions with AST at pH 7.4. A combined approach using fluorescence, UV–vis, and FTIR spectroscopy, along with particle size distribution and zeta potential analyses, was employed. The native BSA–AST, BSA<sub><i>US</i></sub>–AST, and BSA<sub><i>den</i></sub>–AST systems were comparatively evaluated. AST induced static fluorescence quenching in all systems, with a 1:1 binding stoichiometry and binding constants ranging from 10<sup>6</sup> to 10<sup>7</sup>&#xa0;M⁻<sup>1</sup> over the temperature range of 298–318&#xa0;K, following the order BSA–AST &lt; BSA<sub><i>US</i></sub>–AST &lt; BSA<sub><i>den</i></sub>–AST. FTIR analysis revealed that AST increased the protein α-helix and β-sheet contents, accompanied by a reduction in disordered structures and β-turns. The BSA<sub><i>US</i></sub>–AST and BSA<sub><i>den</i></sub>–AST complexes exhibited the highest α-helix contents (68.19% and 67.92%, respectively), and the lowest β-turn fractions (2.49% and 1.95%, respectively). Additionally, in vitro antioxidant activity (DPPH and ABTS) was significantly higher (<i>p</i> &lt; 0.05) in the complexes, particularly in BSA<sub><i>den</i></sub>–AST and BSA<sub><i>US</i></sub>–AST, indicating improved functional accessibility of AST. These findings suggest that protein pre-treatments induce conformational rearrangements that enhance complex stability, thus improving the functional performance of AST. Overall, the results demonstrate that structural modification of BSA provides a favorable balance between binding strength, structural accessibility, and colloidal stability, resulting in improved functional performance of astaxanthin. Thus, thermal and ultrasonic treatments of BSA emerge as promising strategies to improve the stability and functionality in food and delivery systems.</p>

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Conformational Changes Induced by Thermal and Ultrasonic Treatments in Bovine Serum Albumin: Effects on Astaxanthin Binding, Complex Stability, and Antioxidant Activity

  • 期刊论文

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  • 发表日期：

    2026年5月28日

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  • Tatiane Teixeira Tavares,
  • Danielle Cristine Mota Ferreira,
  • Flaviana Coelho Pacheco,
  • Lorena Evangelista Fernandes,
  • Ana Flávia Coelho Pacheco Paiva,
  • Bruno Ricardo de Castro Leite Junior,
  • Paulo Henrique Costa Paiva

摘要

Structural modifications in bovine serum albumin (BSA) may alter its ability to act as a carrier for hydrophobic bioactive compounds such as astaxanthin (AST). This study investigated how thermal denaturation (BSAden) and ultrasonic treatment (BSAUS) affect the conformation of BSA and its interactions with AST at pH 7.4. A combined approach using fluorescence, UV–vis, and FTIR spectroscopy, along with particle size distribution and zeta potential analyses, was employed. The native BSA–AST, BSAUS–AST, and BSAden–AST systems were comparatively evaluated. AST induced static fluorescence quenching in all systems, with a 1:1 binding stoichiometry and binding constants ranging from 106 to 107 M⁻1 over the temperature range of 298–318 K, following the order BSA–AST < BSAUS–AST < BSAden–AST. FTIR analysis revealed that AST increased the protein α-helix and β-sheet contents, accompanied by a reduction in disordered structures and β-turns. The BSAUS–AST and BSAden–AST complexes exhibited the highest α-helix contents (68.19% and 67.92%, respectively), and the lowest β-turn fractions (2.49% and 1.95%, respectively). Additionally, in vitro antioxidant activity (DPPH and ABTS) was significantly higher (p < 0.05) in the complexes, particularly in BSAden–AST and BSAUS–AST, indicating improved functional accessibility of AST. These findings suggest that protein pre-treatments induce conformational rearrangements that enhance complex stability, thus improving the functional performance of AST. Overall, the results demonstrate that structural modification of BSA provides a favorable balance between binding strength, structural accessibility, and colloidal stability, resulting in improved functional performance of astaxanthin. Thus, thermal and ultrasonic treatments of BSA emerge as promising strategies to improve the stability and functionality in food and delivery systems.