Andersson August, Mäler Lena
Department of Biochemistry and Biophysics, Arrhenius Laboratory, Stockholm University, SE-106 91 Stockholm, Sweden.
Langmuir. 2005 Aug 16;21(17):7702-9. doi: 10.1021/la0513003.
The dynamics of DMPC in different isotropic bicelles have been investigated by NMR and EPR methods. The local dynamics were obtained by interpretation of 13C NMR relaxation measurements of DMPC in the bicelles, and these results were compared to EPR spectra of spin-labeled lipids. The overall size of the bicelles was investigated by PFG NMR translational diffusion measurements. The dynamics and relative sizes were compared among three different bicelles: [DMPC]/[DHPC] = 0.25, [DMPC]/[DHPC] = 0.5, and [DMPC]/[CHAPS] = 0.5. The local motion is found to depend much more strongly on the choice of the detergent, rather than the overall size of the bicelle. The results provide an explanation for differences in apparent dynamics for different peptides, which are bound to bicelles. This in turn determines under what conditions reasonable NMR spectra can be observed. A model is presented in which extensive local motion, in conjunction with the overall size, affects the spectral properties. An analytical expression for the size dependence of the bicelles, relating the radius of the bilayer region with physical properties of the detergent and the lipid, is also presented.
通过核磁共振（NMR）和电子顺磁共振（EPR）方法研究了二肉豆蔻酰磷脂酰胆碱（DMPC）在不同各向同性双分子层微团中的动力学。通过对双分子层微团中DMPC的13C NMR弛豫测量结果进行解释获得局部动力学，并将这些结果与自旋标记脂质的EPR光谱进行比较。通过脉冲场梯度NMR平移扩散测量研究双分子层微团的整体大小。比较了三种不同双分子层微团的动力学和相对大小：[DMPC]/[二己酰磷脂酰胆碱（DHPC）]=0.25、[DMPC]/[DHPC]=0.5和[DMPC]/[3-[(3-胆酰胺丙基)二甲基铵基]-1-丙磺酸（CHAPS）]=0.5。发现局部运动对去污剂选择的依赖性比双分子层微团的整体大小更强。这些结果解释了与双分子层微团结合的不同肽表观动力学的差异。这反过来又决定了在何种条件下可以观察到合理的NMR光谱。提出了一个模型，其中广泛的局部运动与整体大小一起影响光谱特性。还给出了双分子层微团大小依赖性的解析表达式，将双层区域的半径与去污剂和脂质的物理性质联系起来。
