Novel Type of Bicellar Disks from a Mixture of DMPC and DMPE-DTPA with Complexed Lanthanides

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• 作者：Paul Beck ; Marianne Liebi ; Joachim Kohlbrecher ; Takashi Ishikawa ; Heinz Regger ; Peter Fischer ; Peter Walde ; Erich Windhab
• 刊名：Langmuir
• 出版年：2010
• 出版时间：April 20, 2010
• 年：2010
• 卷：26
• 期：8
• 页码：5382-5387
• 全文大小：910K
• 年卷期：v.26,no.8(April 20, 2010)
• ISSN：1520-5827

文摘

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 (Tm³⁺) or lanthanum (La³⁺). 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 ³¹P 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 °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 Tm³⁺.