Hybrid lipid/block copolymer vesicles display broad phase coexistence region
Hybrid lipid/block copolymer vesicles display broad phase coexistence region
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杂化脂质/嵌段共聚物囊泡显示出宽相共存区域
DOI：
10.1016/j.bbamem.2021.183552
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Longo, Marjorie L.
中科院分区：
文献类型：
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作者：
Hamada, Naomi;Gakhar, Sukriti;Longo, Marjorie L.
采用双棕榈酰磷脂酰胆碱（DPPC）和聚（1,2-丁二烯）-嵌段聚氧化物（PBd-PEO，平均分子量950 g/mol）的杂化囊泡加热，利用DPH各向异性和laurdan广义极化（GP）荧光光谱技术研究了~100 nm杂化囊泡的流动性和极性环境。这些技术表明，PBd-PEO膜的有序度低于固体DPPC，但略高于液体DPPC或二油基磷脂酰胆碱（DOPC）膜。我们发现DPH各向异性值小于DPPC和PBd-PEO的流体相混合物中各组分各向异性的可加性，推断DPPC强烈流化PBd-PEO。我们利用DPH各向异性的转变和laurdan GP建立了DPPC/PBd-PEO的温度/组成相图，我们发现DPPC/PBd-PEO的固/液共存区域比DPPC/DOPC明显更宽，表明DPPC不容易分裂成流体PBd-PEO，而不容易分裂成流体DOPC。通过Förster共振能量传递结果和室温下含95% PBd-PEO的巨型单层囊泡和含100% PBd-PEO的单层囊泡的相分离可视化，验证了DPPC/PBd-PEO囊泡中存在广泛的固/液共存区。这些结果增加了对杂化囊泡相行为和相图的有限认识，并且应该有助于理解和定制生物医学应用中的膜表面结构，如药物传递或膜蛋白重构。
The fluidity and polar environment of ~100 nm hybrid vesicles combining dipalmitoylphosphatidylcholine (DPPC) and poly(1,2-butadiene)-block-polyethylene oxide (PBd-PEO, average molecular weight 950 g/mol) were studied upon vesicle heating using the fluorescence spectroscopy techniques of DPH anisotropy and laurdan generalized polarization (GP). These techniques indicated PBd-PEO membranes are less ordered than solid DPPC, but slightly more ordered than fluid DPPC or dioleoylphosphatidylcholine (DOPC) membranes. We find the DPH anisotropy values are less than expected from additivity of the components' anisotropies in the fluid phase mixture of DPPC and PBd-PEO, inferring that DPPC strongly fluidizes the PBd-PEO. We use transitions in DPH anisotropy and laurdan GP to create a temperature/composition phase diagram for DPPC/PBd-PEO which we find displays a significantly broader solid/fluid phase coexistence region than DPPC/DOPC, showing that DPPC partitions less readily into fluid PBd-PEO than into fluid DOPC. The existence of a broad solid/fluid phase coexistence region in DPPC/PBd-PEO vesicles is verified by Förster resonance energy transfer results and the visualization of phase separation in giant unilamellar vesicles containing up to 95% PBd-PEO and a single phase in 100% PBd-PEO vesicles at room temperature. These results add to the limited knowledge of phase behavior and phase diagrams of hybrid vesicles, and should be useful in understanding and tailoring membrane surface architecture toward biomedical applications such as drug delivery or membrane protein reconstitution.