title: Probing the interactions of hemoglobin with antioxidant flavonoids via fluorescence spectroscopy and molecular modeling studies.
abstract: Steady state and time resolved fluorescence spectroscopy, combined with molecular modeling computations, have been used to explore the interactions of two therapeutically important flavonoids, fisetin (3,7,3',4'-OH-flavone) and 3-hydroxyflavone (3-HF), with normal human hemoglobin (HbA). Distinctive 'two color' fluorescence signatures and fairly high fluorescence anisotropy (r=0.12-0.28) of fisetin and 3-HF reveal their specific interactions with HbA. Binding constants estimated from the fluorescence studies were ≈4.00 × 10(4)M(-1) and 9.83 × 10(3)M(-1) for fisetin and 3-HF respectively. Specific interactions with HbA were further confirmed from flavonoid-induced static quenching of the protein tryptophan fluorescence as indicated by: (a) bimolecular quenching constant K(q)≫diffusion controlled limit (b) closely matched values of Stern-Volmer quenching constant and binding constant (c) τ(o)/τ≈1 (where τ(o) and τ are the unquenched and quenched tryptophan fluorescence lifetimes respectively). Molecular docking and electrostatic surface potential calculations reveal contrasting binding modes of fisetin and 3-HF with HbA.
authors.affiliation: Biophysics Division, Saha Institute of Nuclear Physics, 1/AF, Bidhannagar, Kolkata 700064, India.
authors.forename: Sudip
authors.initials: S
authors.lastname: Chaudhuri
authors.forename: Sandipan
authors.initials: S
authors.lastname: Chakraborty
authors.forename: Pradeep K
authors.initials: PK
authors.lastname: Sengupta
mesh_terms: D000975:Antioxidants / Q000737:chemistry; D002942:Circular Dichroism / Q000379:methods; D005419:Flavonoids / Q000737:chemistry*; D044948:Flavonols; D006441:Hemoglobin A / Q000737:chemistry*; D006801:Humans; D056004:Molecular Dynamics Simulation; D013050:Spectrometry, Fluorescence / Q000379:methods*; D014364:Tryptophan / Q000737:chemistry
chemical_list: D000975:Antioxidants; D005419:Flavonoids; D044948:Flavonols; D014364:Tryptophan; D006441:Hemoglobin A; C017875:fisetin; C041477:3-hydroxyflavone