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Ether-linked lipids: Spin-label EPR and spin echoes
Chemistry and Physics of Lipids ( IF 3.4 ) Pub Date : 2018-02-02 , DOI: 10.1016/j.chemphyslip.2018.01.010
Maria Oranges , Rita Guzzi , Derek Marsh , Rosa Bartucci

Electron spin echo envelope modulation (ESEEM) and conventional electron paramagnetic resonance (EPR) of site-specifically spin-labelled phospholipids are used to investigate the effect of ether-linked chains on the water-penetration and polarity profiles, as well as the phase behaviour and chain flexibility profiles, of phospholipid membranes. D2O-ESEEM reveals that water exposure of the terminal methyl groups in the interdigitated phase of dihexadecyl phosphatidylcholine (DHPC) is comparable to that of the methylene groups at the polar head-group end of the chains. Similarly, an uniform transmembrane polarity profile is obtained from the dependence of the outer 14N-hyperfine splitting on the spin-label position along the chain in frozen interdigitated DHPC dispersions. Two-component conventional EPR spectra of spin labels at the terminal methyl end of the chain reveal that the intermediate gel phase above the pretransition of DHPC contains components in which the lipid chains are interdigitated. The polarity and chain-flexibility profiles in the fluid Lα-phase of DHPC with ether-linked chains are shifted outwards, towards the polar-apolar interface, as compared with that of dihexadecanoyl phosphatidylcholine (DPPC) with ester-linked chains. Also, the polarity profile of DHPC is shifted upwards, to higher polarities. These differences reflect those in hydrocarbon thickness and area/lipid molecule reported by x-ray diffraction for the Lα-phases of the two lipids.



中文翻译:

醚类脂质:自旋标记EPR和自旋回波

电子自旋回波包络调制(ESEEM)和位点自旋标记的磷脂的常规电子顺磁共振(EPR)用于研究醚连接的链对水渗透性和极性分布以及相行为的影响和磷脂膜的链柔性分布。D 2 O-ESEEM揭示,二十六烷基磷脂酰胆碱(DHPC)的叉指相中末端甲基的水暴露与链的极性头基末端的亚甲基的水暴露相当。类似地,从外部14 N的依赖性获得均匀的跨膜极性分布-冷冻的叉指DHPC分散液中沿链的旋转标记位置发生超细分裂。在链的末端甲基末端的自旋标记物的两组分常规EPR光谱显示,DHPC预转变以上的中间凝胶相包含脂质链相互交叉的组分。与具有酯连接链的二十六烷酰基磷脂酰胆碱(DPPC)相比,具有醚连接链的DHPC的流体相中的极性和链挠性分布朝着极性-非极性界面向外移动。同样,DHPC的极性分布向上移动到更高的极性。这些差异反映了通过X射线衍射观察到的Lα的烃类厚度和面积/脂质分子的差异。脂质的两个相。

更新日期:2018-02-02
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