Liu Ying, Li Ming, Yang Yongkun, Xia Yan, Nieh Mu-Ping
Department of Chemical and Biomolecular Engineering, University of Connecticut, Storrs, CT 06269, USA.
Polymer Program, Institute of Materials Science, University of Connecticut, Storrs, CT 06269, USA.
Biochim Biophys Acta. 2014 Jul;1838(7):1871-80. doi: 10.1016/j.bbamem.2014.02.004. Epub 2014 Feb 21.
The self-assembling morphologies of low-concentration (mostly 1 and 10mg/mL) bicellar mixtures composed of zwitterionic dipalmitoyl (di-C16) phosphatidylcholine (DPPC), dihexanoyl (di-C6) phosphatidylcholine (DHPC), and negatively charged dipalmitoyl (di-C16) phosphatidylglycerol (DPPG) were investigated using small angle neutron scattering, dynamic light scattering and transmission electron microscopy. A polyethylene glycol conjugated (PEGylated) lipid, distearoyl phosphoethanolamine-[methoxy (polyethyleneglycol)-2000] (PEG2000-DSPE), was incorporated in the system at 5mol% of the total lipid composition. The effects of several parameters on the spontaneous structures were studied, including temperature, lipid concentration, salinity, and PEG2000-DSPE. In general, nanodiscs (bicelles) were observed at low temperatures (below the melting temperature, TM of DPPC) depending on the salinity of the solutions. Nanodisc-to-vesicle transition was found upon the elevation of temperature (above TM) in the cases of low lipid concentration in the absence of PEG2000-DSPE or high salinity. Both addition of PEG2000-DSPE and high lipid concentration stabilize the nanodiscs, preventing the formation of multilamellar vesicles, while high salinity promotes vesiculation and the formation of aggregation. This study suggests that the stability of such nanodiscs is presumably controlled by the electrostatic interactions, the steric effect induced by PEG2000-DSPE, and the amount of DHPC located at the disc rim.
使用小角中子散射、动态光散射和透射电子显微镜研究了由两性离子二棕榈酰（二 - C16）磷脂酰胆碱（DPPC）、二己酰（二 - C6）磷脂酰胆碱（DHPC）和带负电荷的二棕榈酰（二 - C16）磷脂酰甘油（DPPG）组成的低浓度（主要为1和10mg/mL）双分子层混合物的自组装形态。一种聚乙二醇共轭（聚乙二醇化）脂质，二硬脂酰磷脂酰乙醇胺 - [甲氧基（聚乙二醇）-2000]（PEG2000 - DSPE），以总脂质组成的5mol%掺入体系中。研究了几个参数对自发结构的影响，包括温度、脂质浓度、盐度和PEG2000 - DSPE。一般来说，在低温（低于DPPC的熔点，TM）下，根据溶液的盐度观察到纳米盘（双分子层）。在不存在PEG2000 - DSPE或高盐度的低脂质浓度情况下，温度升高（高于TM）时会发生纳米盘到囊泡的转变。添加PEG2000 - DSPE和高脂质浓度都能稳定纳米盘，防止多层囊泡的形成，而高盐度则促进囊泡化和聚集的形成。这项研究表明，此类纳米盘的稳定性可能受静电相互作用、PEG2000 - DSPE诱导的空间效应以及位于盘边缘的DHPC量的控制。
