Interaction Between Isoquercitrin and Bovine Serum Albumin by a Multispectroscopic Method

ABSTRACT The interaction of isoquercitrin and bovine serum albumin (BSA) was investigated by means of fluorescence spectroscopy (FS), resonance light scattering spectroscopy (RLS), and ultraviolet spectroscopy (UV). The apparent binding constants (K a) between isoquercitrin and BSA were 5.37 × 105 L mol−1 (293.15 K) and 2.34 × 105 L mol−1 (303.15 K), and the binding site values (n) were 1.18 ± 0.03. According to the Forster theory of non-radiation energy transfer, the binding distances (r) between isoquercitrin and BSA were 1.94 and 1.95 nm at 293.15 K and 303.15 K, respectively. The experimental results showed that the isoquercitrin could be inserted into the BSA, quenching the inner fluorescence by forming the isoquercitrin–BSA complex. The addition of increasing isoquercitrin to BSA solution leads to the gradual enhancement in RLS intensity, exhibiting the formation of the aggregate in solution. It was found that both static quenching and non-radiation energy transfer were the main reasons for the fluo...