| Abstract
| - The interactions of bovine serum albumin (BSA) with cationic gemini surfactants alkanediyl-α,ω-bis(dodecyldimethylammonium bromide) [C12H25(CH3)2N(CH2)SN(CH3)2C12H25]Br2 (designated as C12CSC12Br2, S = 3, 6, and 12) and single-chain surfactant dodecyltrimethylammonium bromide (DTAB) have beenstudied with isothermal titration microcalorimetry, turbidity, fluorescence spectroscopy, and circular dichroismat pH 7.0. Comparing with DTAB, C12CSC12Br2 have much stronger binding ability with BSA to induce thedenaturation of BSA at very low molar ratio of C12CSC12Br2/BSA, and C12CSC12Br2 have a much strongertendency to form insoluble complexes with BSA. The binding of C12CSC12Br2 to BSA generates largerendothermic 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 theseobservations. In addition, the spectra results show that the binding of DTAB to BSA only promotes BSAunfolding and aggregation, whereas the secondary structure of BSA is possibly stabilized by a small amountof C12CSC12Br2, even if the small amount of binding C12CSC12Br2 could induce the loss of the tertiary structureof BSA. This result may be related to the double tails of gemini surfactants, which may generate the hydrophobiclinkages between the nonpolar residues of BSA.
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