Proton NMR based investigation of the effects of temperature and NaCl on micellar properties of CHAPS.
Proton NMR based investigation of the effects of temperature and NaCl on micellar properties of CHAPS.
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DOI：
10.1021/jp108694v
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发表时间：
2011-03
期刊：
影响因子：
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通讯作者：
Xianguo Qin;Maili Liu;Xu Zhang;Daiwen Yang
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文献类型：
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作者：
Xianguo Qin;Maili Liu;Xu Zhang;Daiwen Yang
采用核磁共振波谱技术研究了温度和NaCl对膜蛋白研究中广泛使用的两性离子洗涤剂CHAPS胶束作用的影响。结果表明，CHAPS的两个表观临界胶束浓度（cmc）随温度的升高和NaCl浓度的升高而降低。由温度相关的cmc值得到的热力学参数表明，胶束化过程是自发的、放热的，范德华相互作用可能是导致CHAPS胶束化的主要因素。在100 ~ 600 mM NaCl范围内，胶束水动力半径基本保持不变，说明CHAPS的聚集体状态对周围条件的变化不敏感。此外，核Overhauser效应（NOE）强度对温度的依赖性进一步证明了CHAPS在表观第二cmc以上的浓度下存在独特的交错胶束结构，这是我们之前的工作中提出的。我们的研究结果为优化CHAPS在非变性条件下对膜蛋白的增溶或稳定作用的浓度提供了基础，并有助于了解其与蛋白质的相互作用。
The effects of temperature and NaCl on the micellization of CHAPS, a zwitterionic detergent widely used in membrane protein studies, have been investigated by NMR spectroscopy. We found that the two apparent critical micelle concentration (cmc) values of CHAPS decrease with the increase of temperature, as well as the NaCl concentration. The thermodynamic parameters derived from the temperature-dependent cmc values show that the micellization process is spontaneous and exothermic, and the van der Waals interaction is likely to be the main factor for the micellization of CHAPS. The micellar hydrodynamic radii remain almost the same in a range of 100-600 mM NaCl, indicating that the aggregate states of CHAPS are not sensitive to the change of the surrounding conditions. In addition, the dependence of nuclear Overhauser effect (NOE) intensities on temperatures further demonstrates the existence of the unique staggered micellar structure of CHAPS at a concentration above the apparent second cmc, which was suggested in our previous work. Our results provide a basis for optimizing CHAPS concentration in the solubilization or stabilization of membrane proteins under nondenaturing conditions and may be helpful to understand its interaction with proteins.