Laboratory of Food Process Engineering, ETH Zurich, Schmelzbergstrasse 9, 8092 Zurich, Switzerland.
Langmuir. 2010 Apr 20;26(8):5382-7. doi: 10.1021/la903806a.
We report on the formation of bicelles from a mixture of dimyristoylphosphatidylcholine (DMPC) and the chelator-lipid dimyristoylphosphatidylethanolamine-diethylenetriaminepentaacetate (DMPE-DTPA) with complexed lanthanides, either thulium (Tm(3+)) or lanthanum (La(3+)). The two phospholipids used have the same acyl-chain length but differ in headgroup size and chemical structure. The total lipid concentration was 15 mM, and the molar ratio of DMPC to DMPE-DTPA was 4:1. The system was studied with small angle neutron scattering (SANS) in a magnetic field, cryo-transmission electron microscopy (cryo-TEM), and (31)P NMR spectroscopy. We found that, after appropriate preparation steps, that is, extrusion through a polycarbonate membrane followed by a cooling step, monodisperse small unilamellar disks (flat cylinders called bicelles) are formed. They have a radius of 20 nm and a bilayer thickness of about 4 nm and are stable in the investigated temperature range of 2.5-30 degrees C. Fitting of SANS data with a form factor for partly aligned flat cylinders shows that the bicelles are slightly orientable in a magnetic field of 8 T if DMPE-DTPA is complexed with Tm(3+).
我们报告了由二肉豆蔻酰磷脂酰胆碱（DMPC）和螯合脂质二肉豆蔻酰磷脂酰乙醇胺-二亚乙基三胺五乙酸（DMPE-DTPA）与镱（Tm(3+))或镧（La(3+))配合的镧系元素形成双脂体的情况。所用的两种磷脂酰胆碱具有相同的酰链长度，但头基大小和化学结构不同。总脂质浓度为 15 mM，DMPC 与 DMPE-DTPA 的摩尔比为 4:1。该系统采用小角中子散射（SANS）在磁场中、低温透射电子显微镜（cryo-TEM）和（31）P NMR 光谱进行研究。我们发现，经过适当的准备步骤，即通过聚碳酸酯膜挤出后进行冷却步骤，可以形成单分散的小单层囊泡（称为双脂体的扁平圆柱体）。它们的半径为 20nm，双层厚度约为 4nm，在 2.5-30°C 的研究温度范围内稳定。用部分对齐的扁平圆柱体的形态因子对 SANS 数据进行拟合表明，如果 DMPE-DTPA 与 Tm(3+)配合，则双脂体在 8T 的磁场中具有轻微的可取向性。
