title: Proton NMR based investigation of the effects of temperature and NaCl on micellar properties of CHAPS.
abstract: 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.
authors.affiliation: Wuhan Center for Magnetic Resonance, State Key Laboratory of Magnetic Resonance and Atomic and Molecular Physics, Wuhan Institute of Physics and Mathematics, Chinese Academy of Sciences, Wuhan 430071, China.
authors.forename: Xianguo
authors.initials: X
authors.lastname: Qin
authors.forename: Maili
authors.initials: M
authors.lastname: Liu
authors.forename: Xu
authors.initials: X
authors.lastname: Zhang
authors.forename: Daiwen
authors.initials: D
authors.lastname: Yang
mesh_terms: D002793:Cholic Acids / Q000737:chemistry*; D003902:Detergents / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008823:Micelles; D011522:Protons; D012965:Sodium Chloride / Q000737:chemistry*; D013696:Temperature
chemical_list: D002793:Cholic Acids; D003902:Detergents; D008823:Micelles; D011522:Protons; D012965:Sodium Chloride; C028213:3-((3-cholamidopropyl)dimethylammonium)-1-propanesulfonate