文獻(xiàn)：使用原子力譜法評(píng)估束縛1-棕櫚酰-2-油酰-sn-甘油-3-磷酸膽堿膜的楊氏模量

鏈接：https://pubs.acs.org/doi/abs/10.1021/jp505451h

作者：王曦，羅伯特·N·桑德森?雷吉娜·拉根

摘要：

將由濃度在0 mol %至24 mol %之間的1-棕櫚酰-2-油酰-sn-甘油-3-磷酸膽堿 (POPC) 和不同濃度的1,2-二硬脂酰-sn-甘油-3-磷酸乙醇胺-N-聚乙二醇-2000- N- [3-(2-吡啶基二硫代)丙酸酯] (DSPE-PEG-PDP) 組成的單層囊泡組裝在原子級(jí)平整的模板剝離金 (TS Au) 表面。使用原子力顯微鏡 (AFM) 對(duì)緩沖液中所得束縛脂質(zhì)雙層膜 (tLBM) 進(jìn)行力譜分析，提供了關(guān)于機(jī)械響應(yīng)隨束縛分子 DSPE-PEG-PDP 濃度變化的信息。

楊氏模量通過(guò)使用最近修改的 Sneddon 模型擬合力-壓痕曲線來(lái)確定，該模型校正了來(lái)自下方基質(zhì)的貢獻(xiàn)。在低濃度下，楊氏模量低于支持的 POPC LBM（即直接位于固體基底上）。模量的降低歸因于膜流動(dòng)性的增加，因?yàn)橥ㄟ^(guò)摻入 DSPE-PEG-PDP 束縛基團(tuán)，tLBM 和固體基底之間的耦合減少了。從測(cè)定的楊氏模量值可知，濃度高于 6 mol % 時(shí)，PEG 鏈構(gòu)象決定 tLBM 的剛性。AFM 力譜數(shù)據(jù)分析表明，聚乙二醇 (PEG) 蘑菇到刷子的轉(zhuǎn)變發(fā)生在 6 mol % 附近，這導(dǎo)致 tLBM 在更高的 DSPE-PEG-PDP 濃度下先變軟，然后突然變硬，這與轉(zhuǎn)變有關(guān)。當(dāng) DSPE-PEG-PDP 濃度增加到 24 mol % 時(shí)，AFM 形貌和楊氏模量似乎與另一個(gè)相變相關(guān)； AFM 形貌圖像與雙層盤結(jié)構(gòu)一致，其中 DSPE-PEG-PDP 隔離在盤的邊緣。

Abstract

Unilamellar vesicles composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) with varying 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-poly(ethylene glycol)-2000-N-[3-(2-pyridyldithio) propionate] (DSPE-PEG-PDP) concentration between 0 mol % and 24 mol % were assembled on atomically flat template-stripped gold (TS Au) surfaces. Force spectroscopy, using an atomic force microscope (AFM), of the resulting tethered lipid bilayer membranes (tLBMs) in buffer provided information regarding mechanical response as a function of tethering molecule, DSPE-PEG-PDP, concentration. Young’s modulus was determined by fitting the force–indentation curve with a recently modified Sneddon model that corrects for contributions from the substrate underneath. At low concentrations, Young’s modulus is lower than that of a supported POPC LBM, i.e., directly sitting on a solid substrate. The decrease in modulus is attributed to increased membrane fluidity as coupling between the tLBM and solid substrate is reduced by the incorporation of DSPE-PEG-PDP tethering groups. From the determined Young’s modulus values, the PEG chain conformation is found to dominate tLBM rigidity at concentrations above 6 mol %. Analysis of AFM force spectroscopy data indicates that the poly(ethylene glycol) (PEG) mushroom to brush transition occurs near 6 mol %, and this leads to first softening and then abrupt stiffening of tLBMs at higher DSPE-PEG-PDP concentration associated with the transition. When DSPE-PEG-PDP concentration is increased to 24 mol %, AFM topography and Young’s modulus appear correlated with another phase transition; AFM topography images are consistent with a bilayer disk structure with DSPE-PEG-PDP segregated at the rim of the disk.

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DSPE-PEG-Cy5.5

DSPE-PEG-Cy7

DSPE-PEG-NBD

DSPE-PEG-TRITC

DSPE-PEG-Comarin

DSPE-PEG-ICG

DSPE-PEG-Pyrene

DSPE-PEG-Ce6

DSPE-PEG-Cy3

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