Binding of antioxidant flavonol morin to the native state of bovine serum albumin: Effects of urea and metal ions on the binding

In consideration of the various medicinal aspects of the flavonoid polyphenols, the interaction of morin with bovine serum albumin (BSA) has been investigated using multi-spectroscopic approaches. The pKa1 of morin being 5.09, which is below physiological pH, binding studies provide important insights into its potential use as a biotherapeutic. The binding was performed under different pH (5, 7 and 9) conditions and in absence and presence of Cu(II) and Fe(III) ions. It is observed that the presence of metal ions affect the binding of morin towards BSA. The binding with BSA results in a motional restriction of morin in solution that causes an increase in anisotropy (r), rotational correlation time (tr) and steady-state lifetime (tav) of the ligand. Urea causes denaturation of BSA resulting in the release of morin from the protein core as determined from both the steady-state fluorescence and anisotropy (r) measurements. The possibility of non-radiative energy transfer from the donor tryptophan to the acceptor morin is detected following the Försterʹs theory. The site marker displacement studies along with the molecular docking results indicated that morin binds to the hydrophobic pocket of site 1 (subdomain IIA) near Trp 213 of BSA.