Fluorescence studies of dehydroergosterol in phosphatidylethanolamine/phosphatidylcholine bilayers
Fluorescence studies of dehydroergosterol in phosphatidylethanolamine/phosphatidylcholine bilayers
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DOI：
10.1016/s0006-3495(99)77141-9
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发表时间：
1999-12-01
影响因子：
3.4
通讯作者：
Somerharju, P
中科院分区：
文献类型：
--
作者：
Cheng, KH;Virtanen, J;Somerharju, P
我们先前的荧光研究提供了间接证据，即脂质头基组分倾向于适应流体磷脂酰乙醇胺/磷脂酰胆碱（PE/PC）双层中的规则的超晶格样横向分布（Cheng等人，1997，Biophys. J. 73：1967-1976）。本文利用甾醇探针脱氢麦角甾醇（DHE）的荧光性质，对这一有趣的现象进行了进一步的研究。在23 ℃下测量了DHE在1-棕榈酰-2-油酰-PC（POPC）/1-棕榈酰-2-油酰-PE（POPE）混合物中的荧光发射光谱、荧光各向异性（r）和时间分辨荧光强度衰减作为POPE雄性分数（X-PE）的函数。在X-PE处发现DHE与PE组成图的375 nm处的荧光峰强度/390 nm处的荧光峰强度的比率（1（375）/1（390））、荧光衰减寿命（τ）或旋转相关时间（ω）的偏差，包括下降或扭结，接近0.10、0.25、0.33、0.65、0.75和0.88。对于所有测量参数，始终观察到X-PE的临界值约为0.33和0.65。此外，在23 ℃退火10天后，X-PE < 0.50的凹陷的位置而不是深度没有显著变化。所观察到的X-PE的临界值与由头基超晶格模型预测的一些临界摩尔分数一致（在+/-0.03内），该模型提出PE和PC头基倾向于规则地分布在双层的平面中。这些结果与我们先前使用联芘IPC和Laurdan探针的荧光研究中获得的结果一致，因此支持以下命题：1）在流体PE/PC双层中存在结构域内的规则排列，和2）超晶格形成可能在控制细胞膜的脂质组成中起重要作用（Virtanen等人，1993，Proc.Natl. Acad. Sci. USA. 95：4964-4969）。目前的数据提供了关于这种超晶格畴的物理性质的新信息，即，膜甾醇的介电环境和旋转运动似乎突然改变，因为脂质头基在流体双层中表现出规则的超晶格样分布。
Our previous fluorescence study has provided indirect evidence that lipid headgroup components tend to adapt regular, superlattice-like lateral distribution in fluid phosphatidylethanolamine/phosphatidylcholine (PE/PC) bilayers (Cheng et al., 1997, Biophys. J. 73:1967-1976). Here we have further studied this intriguing phenomenon by making use of the fluorescence properties of a sterol probe, dehydroergosterol (DHE). Fluorescence emission spectra, fluorescence anisotropy (r), and time-resolved fluorescence intensity decays of DHE in 1-palmitoyl-2-oleoyl-PC (POPC)/1-palmitoyl-2-oleoyl-PE (POPE) mixtures were measured as a function of POPE male fraction (X-PE,) at 23 degrees C. Deviations, including dips or kinks, in the ratio of fluorescence peak intensity at 375 nm/fluorescence peak intensity at 390 nm (l(375)/l(390)),fluorescence decay lifetime (7), or rotational correlation time Co) of DHE versus PE composition plots were found at X-PE approximate to 0.10, 0.25, 0.33, 0.65, 0.75, and 0.88. The critical values at X-PE approximate to 0.33 and 0.65 were consistently observed for all measured parameters. in addition, the locations, but not the depth, of the dips for X-PE < 0.50 did not vary significantly over 10 days of annealing at 23 degrees C. The observed critical values of X-PE,, coincide (within +/-0.03) with some of the critical mole fractions predicted by a headgroup superlattice model proposing that the PE and PC headgroups tend to be regularly distributed in the plane of the bilayer. These results agree favorably with those obtained in our previous fluorescence study using dipyrenyIPC and Laurdan probes and thus support the proposition that 1) regular arrangement within a domain exists in fluid PE/PC bilayers, and 2) superlattice formation may play a significant role in controlling the lipid composition of cellular membranes (Virtanen et al., 1993, Proc. Natl. Acad. Sci. USA. 95:4964-4969). The present data provide new information on the physical properties of such superlattice domains, i.e., the dielectric environment and rotational motion of membrane sterols appear to change abruptly as the lipid headgroups exhibit regular superlattice-like distributions in fluid bilayers.