The effect of Cu2+ on interaction between flavonoids with different C-ring substituents and bovine serum albumin: structure-affinity relationship aspect |
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Authors: | Zhang Yuping Shi Shuyun Sun Xiaorui Xiong Xiang Peng Mijun |
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Institution: | a School of Chemistry and Chemical Engineering, Central South University, Changsha 410083, Chinab Key Laboratory of Resources Chemistry of Nonferrous Metals, Central South University, Changsha 410083, Chinac State Key Laboratory of Powder Metallurgy, Central South University, Changsha 410083, Chinad Key Laboratory of Hunan Forest Products and Chemical Industry Engineering, Jishou University, Zhangjiajie 427000, China |
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Abstract: | Four flavonoids quercetin (QU), luteolin (LU), taxifolin (TA) and (+)-catechin (CA) with the same A- and B-rings but different C-ring substituents have been investigated for their binding to bovine serum albumin (BSA) in the absence and presence of Cu2+ by means of various spectroscopic methods such as fluorescence, UV-visible and circular dichroism (CD). The results indicated that hydroxyl group at 3-position increased the binding affinities between flavonoids and BSA. The values of the binding affinities were in the order: QU > CA > TA > LU. The presence of Cu2+ affected the interactions of flavonoids with BSA significantly. The binding affinities of QU and TA for BSA were decreased about 6.7% and 13.2%. However, the binding affinities of LU and CA for BSA were increased about 43.0% and 20.7%. The formation of Cu2+-flavonoid complex and steric hindrance together influenced the binding affinities of QU, LU and TA for BSA, while the conformational change of BSA may be the main reason for the increased binding affinity of CA for BSA. However, the quenching mechanism for QU, LU, TA and CA to BSA was based on static quenching combined with non-radiative energy transfer irrespective of the absence or presence of Cu2+. The UV-visible results showed the change in BSA conformation and the formation of flavonoid-Cu2+ complex. The CD results also explained the conformational changes of BSA on binding with flavonoids. |
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Keywords: | Flavonoid Bovine serum albumin Chemical structure Fluorescence quenching Cu2+ Interaction |
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