Encapsulation of testosterone and its aliphatic and aromatic dimers by milk beta-lactoglobulin.
The encapsulation of testosterone and it aliphatic dimer (alip) and aromatic dimer (arom) with milk β-lactoglobulin (β-LG) was studied in aqueous solution at pH 7.4. Multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were used to characterize testosterone-β-LG binding and protein aggregation process. Spectroscopic analysis showed that steroids bind β-LG via hydrophobic and H-bonding interactions with overall binding constants K test-β-LG = 5.6 (± 0.6) × 10(4)M(-1), K test-dimeralip-β-LG = 4.8 (± 0.5) × 10(3)M(-1) and K test-dimer-arom-β-LG = 2.9 (± 0.4) × 10(4)M(-1). The binding affinity was testosterone > testosterone dimer-aromatic > testosterone dimer-aliphatic. Transmission electron microscopy showed major changes in protein morphology as testosterone-protein complexation occurred with increase in the diameter of the protein aggregate indicating encapsulation of steroids by β-LG. Modeling showed the presence of H-bonding stabilized testosterone-β-LG complexes with the free binding energy of -9.82 Kcal/mol indicating that the interaction process is spontaneous at room temperature.
Department of Chemistry-Biochemistry and Physics, University of Québec at Trois-Riviéres C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada.
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Chanphai
Department of Chemistry-Biochemistry and Physics, University of Québec at Trois-Riviéres C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada.
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Vesper
Department of Chemistry-Biochemistry and Physics, University of Québec at Trois-Riviéres C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada.
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Bekale
Department of Chemistry-Biochemistry and Physics, University of Québec at Trois-Riviéres C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada.
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Bérubé
Department of Chemistry-Biochemistry and Physics, University of Québec at Trois-Riviéres C. P. 500, Trois-Rivières, Québec, G9A 5H7, Canada. Electronic address: heidar-ali.tajmir-riahi@uqtr.ca.
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Tajmir-Riahi
D000818:Animals; D001665:Binding Sites; D004339:Drug Compounding; D007782:Lactoglobulins / Q000737:chemistry*; D008892:Milk / Q000737:chemistry*; D008958:Models, Molecular; D008968:Molecular Conformation; D011485:Protein Binding; D017550:Spectroscopy, Fourier Transform Infrared; D013739:Testosterone / Q000008:administration & dosage* / Q000737:chemistry*
D007782:Lactoglobulins; D013739:Testosterone
Beta-lactoglobulin; Encapsulation; Modeling; TEM; Testosterone; Testosterone dimers