Li Yajuan, Wang Xiaoyong, Wang Yilin
Key Laboratory of Colloid and Interface Science, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100080, People's Republic of China.
J Phys Chem B. 2006 Apr 27;110(16):8499-505. doi: 10.1021/jp060532n.
The interactions of bovine serum albumin (BSA) with cationic gemini surfactants alkanediyl-alpha,omega-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)(S)N(CH3)2C12H25]Br2 (designated as C12C(S)C12Br2, S = 3, 6, and 12) and single-chain surfactant dodecyltrimethylammonium bromide (DTAB) have been studied with isothermal titration microcalorimetry, turbidity, fluorescence spectroscopy, and circular dichroism at pH 7.0. Comparing with DTAB, C12C(S)C12Br2 have much stronger binding ability with BSA to induce the denaturation of BSA at very low molar ratio of C12C(S)C12Br2/BSA, and C12C(S)C12Br2 have a much stronger tendency to form insoluble complexes with BSA. The binding of C12C(S)C12Br2 to BSA generates larger endothermic peaks. The first endothermic peak is much stronger than that of the second endothermic peak. The double charges and strong hydrophobicity of the gemini surfactants are the main reasons for these observations. In addition, the spectra results show that the binding of DTAB to BSA only promotes BSA unfolding and aggregation, whereas the secondary structure of BSA is possibly stabilized by a small amount of C12C(S)C12Br2 , even if the small amount of binding C12C(S)C12Br2 could induce the loss of the tertiary structure of BSA. This result may be related to the double tails of gemini surfactants, which may generate the hydrophobic linkages between the nonpolar residues of BSA.
在pH 7.0条件下，采用等温滴定量热法、浊度法、荧光光谱法和圆二色光谱法研究了牛血清白蛋白（BSA）与阳离子双子表面活性剂链烷二基-α,ω-双（十二烷基二甲基溴化铵）[C12H25(CH3)2N(CH2)(S)N(CH3)2C12H25]Br2（表示为C12C(S)C12Br2，S = 3、6和12）以及单链表面活性剂十二烷基三甲基溴化铵（DTAB）之间的相互作用。与DTAB相比，C12C(S)C12Br2与BSA具有更强的结合能力，在极低的C12C(S)C12Br2/BSA摩尔比下就能诱导BSA变性，并且C12C(S)C12Br2与BSA形成不溶性复合物的倾向更强。C12C(S)C12Br2与BSA的结合产生更大的吸热峰。第一个吸热峰比第二个吸热峰强得多。双子表面活性剂的双电荷和强疏水性是这些现象的主要原因。此外，光谱结果表明，DTAB与BSA的结合仅促进BSA的展开和聚集，而即使少量结合的C12C(S)C12Br2会导致BSA三级结构的丧失，少量的C12C(S)C12Br2也可能使BSA的二级结构稳定。这一结果可能与双子表面活性剂的双尾有关，双尾可能在BSA的非极性残基之间产生疏水连接。
