Ni Cheng,Xiaoyuan Ma,Xiang Sheng,Tao Wang,Rui Wang,Jingjing Jiao,Li Yu
Two structurally similar imidazolium-based anionic surface active ionic liquids (SAILs) with double hydrocarbon chains, viz. 1-butyl-3-methylimidazolium bis(2-ethylhexyl) sulfosuccinate (C 4 mim-AOT) and 1-butyl-3-methylimidazolium bis(2-ethylhexyl) phosphate (C 4 mim-DEHP), were synthesized by a straightforward ion-exchange technique. A comparative investigation of their aggregation behavior with the corresponding traditional anionic surfactants, sodium bis(2-ethylhexyl) sulfosuccinate (Na-AOT) and sodium bis(2-ethylhexyl) phosphate (Na-DEHP) in aqueous solution was performed in detail by surface tension, electric conductivity, fluorescence spectra and dynamic light scattering measurements. The critical micelle concentration (CMC) values for the surfactants with double hydrocarbon chains obtained by different techniques are in good agreement. The surface activity of C 4 mim-AOT and C 4 mim-DEHP is superior to that of the corresponding traditional anionic surfactants, Na-AOT and Na-DEHP. It is also found that for anionic SAILs the nature of the anionic active group is a dominant factor in the determination of their aggregation behavior in aqueous solution, e.g. CMC and aggregation number, while the introduced organic cation plays a minor role. Theoretical calculations show that more conformations and electronegativity for DEHP anion leads to higher aggregation number and CMC values for C 4 mim-DEHP. This work is expected to be of practical values for the environmental friendly anion SAILs in nanomaterial synthesis and phase separation, etc.
The interactions of Gemini surfactants 1-dodecyl- N , N ′-[(1,4-dioxo-1,4-butanediyl)bis(oxy-2,1-ethanediyl)]bis[ N , N ′-dimethylammonium]dibromide (12-su-12) and 1-dodecyl- N , N ′-[((2 E )-1,4-dioxo-2-butene-1,4-diyl)bis(oxy-2,1-ethanediyl)]bis[ N , N ′-dimethylammonium]dibromide (12-fo-12) and the corresponding single-chain surfactant 1-dodecyl- N -[2-(acetyloxy)ethyl]- N , N -dimethyl ammonium bromide (DTAAB) with bovine serum albumin (BSA) were investigated by conductometry, fluorimetry, UV–vis and CD spectrometry, and dynamic light scattering. It was found that the bindings of all three surfactants to BSA were cooperatively driven by electrostatic and hydrophobic interactions. The Gemini surfactants, carrying more charges and hydrophobic tails, showed stronger interactions with BSA than the single-chain surfactant. The presence of the double bond in the spacer of 12-fo-12 enhanced the interaction between the surfactant and BSA and also significantly varied the binding sites as compared to 12-su-12 and DTAAB, which indicated an important role of the property of the spacer in the interaction between the surfactant and BSA.
The interactions of human serum albumin (HSA) with four cationic gemini surfactants and four single-chain surfactants have been investigated from the measurements of fluorescence spectroscopy, dynamic lights scattering (DLS), zeta potential, and circular dichroism (CD). The fluorescence results show the binding strength of surfactants to HSA, along with the blue shift under the maximum emission wavelength ( λ max ) which is sensitive to the protein conformations. It has been found that the hydrodynamic diameters of the protein aggregates are enlarged and the electrokinetic potentials of them get positive with increasing the concentration of the surfactants. The conformational transformation of the secondary structures of surfactant–HSA aggregates has been confirmed through the quantitative analysis of the CD spectra. The isothermal titration microcalorimetry (ITC) has been employed to further analyze the binding process of single-chain surfactants to HSA. The comprehensive results obtained from various approaches have shown that both hydrophobic and electrostatic interactions are present in the cationic surfactant–HSA systems. Compared with the corresponding single-chain surfactants, the gemini ones have much stronger binding ability to induce the unfolding of HSA. These investigations on the interactions between HSA and surfactants with the altered chain architecture in different concentration regimes can facilitate the application of surfactant-protein systems in pharmaceutical, biotechnology and related fields.
危险品化学品经营许可证（带存储）