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二十二碳六烯酸和胆固醇对磷脂混合物中侧向脂质组织的影响。

Influence of docosahexaenoic acid and cholesterol on lateral lipid organization in phospholipid mixtures.

作者信息

Huster D, Arnold K, Gawrisch K

机构信息

Laboratory of Membrane Biochemistry and Biophysics, NIAAA, National Institutes of Health, Rockville, Maryland 20852, USA.

出版信息

Biochemistry. 1998 Dec 8;37(49):17299-308. doi: 10.1021/bi980078g.

Abstract

We investigated lateral lipid organization in membranes with a lipid composition relevant to neural and retinal membranes [phosphatidylcholine (PC)/phosphatidylethanolamine (PE)/phosphatidylserine (PS)/cholesterol, 4/4/1/1, mol/mol/mol/mol]. The mixed-chain phospholipids contained saturated stearic acid (18:0) in the sn-1 position and the monounsaturated oleic acid (18:1) or polyunsaturated docosahexaenoic acid (22:6) in sn-2. Lateral lipid organization was evaluated by 2H NMR order parameter measurements on stearic acid of all individual types of phospholipids in the mixture and, through a novel approach, two-dimensional NOESY 1H NMR spectroscopy with magic angle spinning (MAS). The docosahexaenoic acid chain order was evaluated from 1H NMR chain signal MAS-sideband intensities. Averaged over all lipids, the cholesterol-induced increase in sn-1 chain order is 2-fold larger in monounsaturated than in polyunsaturated lipids, and the order of both saturated and polyunsaturated hydrocarbon chains increases. Addition of cholesterol increases lipid order in the sequence 18:0-18:1 PE > 18:0-18:1 PC > 18:0-18:1 PS for the monounsaturated and 18:0-22:6 PC >> 18:0-22:6 PE > 18:0-22:6 PS for polyunsaturated mixtures. The variation of order parameters between lipid species suggests that cholesterol induces the formation of lipid microdomains with a headgroup and chain unsaturation-dependent lipid composition. The preferential interaction between cholesterol and polyunsaturated 18:0-22:6 PC, followed by 18:0-22:6 PE and 18:0-22:6 PS, was confirmed by 1H MAS NOESY cross-relaxation rate differences. Furthermore, cholesterol preferentially associates with saturated chains in mixed-chain lipids reflected by higher saturated chain-to-cholesterol cross-relaxation rates. We propose that cholesterol forms PC-enriched microdomains in the polyunsaturated 18:0-22:6 PC/18:0-22:6 PE/18:0-22:6 PS/cholesterol membranes in which the saturated sn-1 chains are preferentially oriented toward the cholesterol molecules.

摘要

我们研究了具有与神经和视网膜膜相关脂质组成的膜中的横向脂质组织[磷脂酰胆碱(PC)/磷脂酰乙醇胺(PE)/磷脂酰丝氨酸(PS)/胆固醇,4/4/1/1,摩尔/摩尔/摩尔/摩尔]。混合链磷脂在sn-1位含有饱和硬脂酸(18:0),在sn-2位含有单不饱和油酸(18:1)或多不饱和二十二碳六烯酸(22:6)。通过对混合物中所有单个类型磷脂的硬脂酸进行2H NMR序参数测量,并通过一种新方法,即二维NOESY 1H NMR光谱结合魔角旋转(MAS)来评估横向脂质组织。从1H NMR链信号MAS边带强度评估二十二碳六烯酸链序。在所有脂质中平均来看,胆固醇诱导的sn-1链序增加在单不饱和脂质中是多不饱和脂质中的2倍,并且饱和和多不饱和烃链的序均增加。对于单不饱和混合物,添加胆固醇会按18:0-18:1 PE > 18:0-18:1 PC > 18:0-18:1 PS的顺序增加脂质序;对于多不饱和混合物,则按18:0-22:6 PC >> 18:0-22:6 PE > 18:0-22:6 PS的顺序增加脂质序。脂质种类之间序参数的变化表明胆固醇诱导形成了具有头基团和链不饱和度依赖性脂质组成的脂质微区。通过1H MAS NOESY交叉弛豫速率差异证实了胆固醇与多不饱和18:0-22:6 PC之间的优先相互作用,其次是18:0-22:6 PE和18:0-22:6 PS。此外,胆固醇优先与混合链脂质中的饱和链结合,这通过较高的饱和链与胆固醇交叉弛豫速率反映出来。我们提出胆固醇在多不饱和18:0-22:6 PC/18:0-22:6 PE/18:0-22:6 PS/胆固醇膜中形成富含PC的微区,其中饱和的sn-1链优先朝向胆固醇分子定向。

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