title: Transporting testosterone and its dimers by serum proteins.
abstract: A substantial part of steroids is bound to serum proteins in vivo. We report the association of testosterone and it aliphatic dimer (alip) and aromatic dimer (arom) with human serum albumin (HSA) and bovine serum albumin (BSA) in aqueous solution at physiological pH. Multiple spectroscopic methods, transmission electron microscopy (TEM) and molecular modeling were used to characterize steroid-protein binding and protein aggregation process. Spectroscopic analysis showed that steroids bind protein via hydrophobic, hydrophilic and H-bonding interactions. HSA forms more stable complexes than BSA. The binding affinity of steroid-protein adducts is testosterone>dimer-aromatic>dimer-aliphatic. Transmission electron microscopy showed major changes in protein morphology as steroid-protein complexation occurred with increase in the diameter of the protein aggregate indicating encapsulation of steroids by serum proteins. Modeling showed the presence of H-bonding stabilized testosterone-protein complexes with the free binding energy of -12.95 for HSA and -11.55 kcal/mol for BSA, indicating that the interaction process is spontaneous at room temperature. Steroid complexation induced more perturbations of BSA conformation than HSA.
authors.affiliation: Department of Chemistry, Biochemistry and Physics, University of Québec at Trois-Rivières, C. P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: P
authors.initials: P
authors.lastname: Chanphai
authors.affiliation: Department of Chemistry, Biochemistry and Physics, University of Québec at Trois-Rivières, C. P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: A R
authors.initials: AR
authors.lastname: Vesper
authors.affiliation: Department of Chemistry, Biochemistry and Physics, University of Québec at Trois-Rivières, C. P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: L
authors.initials: L
authors.lastname: Bekale
authors.affiliation: Department of Chemistry, Biochemistry and Physics, University of Québec at Trois-Rivières, C. P. 500, Trois-Rivières, QC G9A 5H7, Canada.
authors.forename: G
authors.initials: G
authors.lastname: Bérubé
authors.affiliation: Department of Chemistry, Biochemistry and Physics, University of Québec at Trois-Rivières, C. P. 500, Trois-Rivières, QC G9A 5H7, Canada. Electronic address: tajmirri@uqtr.ca.
authors.forename: H A
authors.initials: HA
authors.lastname: Tajmir-Riahi
mesh_terms: D000818:Animals; D001665:Binding Sites; D002417:Cattle; D019281:Dimerization; D006801:Humans; D006860:Hydrogen Bonding; D057927:Hydrophobic and Hydrophilic Interactions; D046529:Microscopy, Electron, Transmission; D062105:Molecular Docking Simulation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D012710:Serum Albumin, Bovine / Q000737:chemistry / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013739:Testosterone / Q000737:chemistry / Q000378:metabolism*; D013816:Thermodynamics
chemical_list: D012709:Serum Albumin; D012710:Serum Albumin, Bovine; D013739:Testosterone
keywords: Binding; Modeling; Morphology; Serum albumin; TEM; Testosterone