Characterization of phospholipid mixed micelles by translational diffusion
Characterization of phospholipid mixed micelles by translational diffusion
复制标题
DOI：
10.1023/b:jnmr.0000032560.43738.6a
复制
发表时间：
2004-07-01
影响因子：
2.7
通讯作者：
Bax, A
中科院分区：
文献类型：
--
作者：
Chou, JJ;Baber, JL;Bax, A
已经测量了一系列胶束和混合胶束系统的平移自扩散速率D-s的浓度依赖性。在纵向涡流延迟实验中使用双极梯度脉冲对最大限度地减少了NOE衰减，并且被发现对于优化大分子和聚集体的平移扩散测量的灵敏度至关重要。对于胶束的低体积分数Phi（Phi小于或等于15%v/v），结合使用D-s = D-o（1 - 3.2 μ daPhi）关系的浓度依赖性的实验测量产生流体动力学体积。对于蛋白质，流体动力学体积，来自D-s在无限稀释浓度，被发现是约2.6倍的未水合分子体积。使用鸡蛋白色溶菌酶作为参考收集的数据，二己酰磷脂酰胆碱（DHPC）胶束的扩散数据表明每个胶束约27个分子，和14 mM的临界胶束浓度。翻译扩散速率的差异，洗涤剂和长链磷脂在混合胶束是由于自由和胶束结合的洗涤剂之间的快速交换。这种差异允许测定游离去污剂浓度，对于高去污剂与长链磷脂的摩尔比，发现游离去污剂浓度强烈依赖于该比例。DHPC/POPC双胞的流体动力学体积，加载M2通道肽同系物，来自平移扩散，预测旋转相关时间，略超过从肽N-15弛豫数据获得的值。
The concentration dependence of the translational self diffusion rate, D-s, has been measured for a range of micelle and mixed micelle systems. Use of bipolar gradient pulse pairs in the longitudinal eddy current delay experiment minimizes NOE attenuation and is found critical for optimizing sensitivity of the translational diffusion measurement of macromolecules and aggregates. For low volume fractions Phi (Phi less than or equal to 15% v/v) of the micelles, experimental measurement of the concentration dependence, combined with use of the D-s = D-o(1-3.2lambdaPhi) relationship, yields the hydrodynamic volume. For proteins, the hydrodynamic volume, derived from D-s at infinitely dilute concentration, is found to be about 2.6 times the unhydrated molecular volume. Using the data collected for hen egg white lysozyme as a reference, diffusion data for dihexanoyl phosphatidylcholine (DHPC) micelles indicate approximately 27 molecules per micelle, and a critical micelle concentration of 14 mM. Differences in translational diffusion rates for detergent and long chain phospholipids in mixed micelles are attributed to rapid exchange between free and micelle-bound detergent. This difference permits determination of the free detergent concentration, which, for a high detergent to long chain phospholipid molar ratio, is found to depend strongly on this ratio. The hydrodynamic volume of DHPC/POPC bicelles, loaded with an M2 channel peptide homolog, derived from translational diffusion, predicts a rotational correlation time that slightly exceeds the value obtained from peptide N-15 relaxation data.