The interactions between lysozyme (Lys) and naringein or naringin were studied by fluorescence spectroscopy under 50% CH₃OH/water circumstance. The binding constants and bind distance of naringein- Lys and naringin-Lys were calculated according to Lineweaver-Burk equation and Föster’ energy transfer theory, which were shown as K_Naringein^{25 ℃}＝4.00×10⁴, r_Naringein＝3.21 nm and K_Naringin^{25 ℃}＝3.48×10⁴, r_Naringin＝3.30 nm, respectively. The results showed that both of them could form non-covalent compounds with Lys mainly through hydrophobic interaction force. Relative to naringein, the binding affinity of naringin to Lys decreased obviously. These suggested that the sugar substitution in the structure of flavonoid is not helpful to the binding of flavonoid-protein. According to the polyphen-protein interaction mode presented by Haslam, the reason resulted in weaker bonding affinity of naringin to Lys was analysed in the level of molecule.

Key words: fluorescence spectroscopy, lysozyme, naringein, naringin, energy transfer