Wisniewska Anna, Subczynski Witold K
Department of Biophysics, Medical College of Wisconsin, Milwaukee, WI 53226, USA.
Free Radic Biol Med. 2006 Oct 15;41(8):1257-65. doi: 10.1016/j.freeradbiomed.2006.07.003. Epub 2006 Jul 11.
A model of photoreceptor outer segment (POS) membranes has been proposed, consisting of an equimolar ternary mixture of 1-palmitoyl-2-docosahexaenoylphosphatidylcholine/distearoylphosphatidylcholine/cholesterol. It was shown that, as in membranes made from the raft-forming mixture, in the model of POS membranes, two domains are formed: the raft domain (detergent resistant membranes, DRM), and the bulk domain (detergent soluble membranes, DSM). Saturation-recovery EPR discrimination by oxygen transport method also demonstrated the presence of two domains in this model system in situ at a wide range of temperatures (10-55 degrees C), showing additionally that neither lutein nor zeaxanthin at 1 mol% affect the formation of these domains. These membrane domains have been separated using cold Triton X-100 extraction from a model of POS membranes containing 1 mol% of either lutein or zeaxanthin. The results indicated that the macular xanthophylls lutein and zeaxanthin are substantially excluded from DRM and remain concentrated in DSM, a domain enriched in highly unsaturated docosahexaenoyl acid which is abundant in retina membranes. The concentration of xanthophylls in DRM and DSM calculated as the mol ratio of either xanthophyll to total lipid (phospholipid+cholesterol) was 0.0028 and 0.0391, respectively. Thus, xanthophylls are about 14 times more concentrated in DSM than in DRM. No significant difference in the distribution of lutein and zeaxanthin was found. The obtained results suggest that in POS membranes macular xanthophylls should also be concentrated in domains enriched in polyunsaturated chains.
有人提出了一种光感受器外段（POS）膜模型，该模型由1-棕榈酰-2-二十二碳六烯酰磷脂酰胆碱/二硬脂酰磷脂酰胆碱/胆固醇的等摩尔三元混合物组成。结果表明，与由筏状形成混合物制成的膜一样，在POS膜模型中形成了两个结构域：筏状结构域（抗去污剂膜，DRM）和主体结构域（去污剂可溶膜，DSM）。通过氧传输方法进行的饱和恢复EPR鉴别还表明，在该模型系统中，在很宽的温度范围（10-55摄氏度）内原位存在两个结构域，此外还表明，1摩尔百分比的叶黄素和玉米黄质均不影响这些结构域的形成。使用冷的 Triton X-100从含有1摩尔百分比叶黄素或玉米黄质的POS膜模型中提取分离了这些膜结构域。结果表明，黄斑叶黄素叶黄素和玉米黄质基本上被排除在DRM之外，并仍然集中在DSM中，DSM是一个富含高度不饱和二十二碳六烯酸的结构域，在视网膜膜中含量丰富。以叶黄素与总脂质（磷脂+胆固醇）的摩尔比计算，DRM和DSM中叶黄素的浓度分别为0.0028和0.0391。因此，叶黄素在DSM中的浓度比在DRM中高约14倍。未发现叶黄素和玉米黄质的分布有显著差异。所得结果表明，在POS膜中，黄斑叶黄素也应集中在富含多不饱和链的结构域中。
