棉酚及其氧化物与牛血清蛋白相互作用的研究

Interaction of Gossypol and Its Oxide with Bovine Serum Albumin

利用紫外-可见吸收光谱和荧光光谱法研究棉酚及其氧化物与牛血清蛋白(bovine serum albumin,BSA)的结合作用。实验结果表明,棉酚及其氧化物与牛血清蛋白相互作用而引起的荧光猝灭机制均属于动态和静态的联合猝灭,BSA发射峰蓝移。通过计算各个结合参数得出:棉酚及其氧化物与BSA的结合常数在105数量级,说明棉酚及其氧化物与BSA有很强的结合,结合位点均为1;热力学参数ΔH<0、ΔS>0和ΔG<0,表明棉酚及其氧化物与BSA结合的主要作用力为疏水作用力和氢键。根据Forster的非辐射能量转移理论,计算供体(BSA)与受体(棉酚及其氧化物)间的结合距离r分别为2.94 nm和3.12 nm,它们都能以能量转移的方式与BSA发生作用。紫外-可见光谱、同步荧光光谱和三维荧光光谱的研究结果表明,棉酚及其氧化物与BSA的结合引起了BSA的构象变化。

The interaction of gossypol and its oxide with bovine serum albumin(BSA) was investigated by fluorescence spectroscopy and ultraviolet-visible spectroscopy(UV-vis). The experimental results indicated that the quenching mechanism of BSA by gossypol and its oxide was a combined dynamic and static quenching, with a blue-shift of the emission maximum of BSA. The calculation of various binding parameters showed that the binding constants for gossypol-BSA and gossypol oxide-BSA were in the order of 105, indicating a strong interaction between gossypol/gossypol oxide and BSA. There was one binding site involved in the interaction between gossypol/gossypol oxide and BSA. The negative value of ΔH, positive value of ΔS, and negative value of ΔG indicated that hydrophobic and hydrogen-bonding interactions played major roles in the binding of gossypol or its oxide with BSA. Based on Forster-type nonradiative energy transfer, the binding distances(r) between the donor(BSA) and acceptor(gossypol or its oxide) were 2.94 nm and 3.12 nm, respectively, and they could interact with BSA by energy transfer. The UV-vis absorption spectra, synchronous fluorescence spectra, and three-dimensional fluorescence spectra showed that the binding of gossypol/gossypol oxide to BSA induced conformational changes in BSA.