Sujak Agnieszka, Gabrielska Janina, Milanowska Justyna, Mazurek Piotr, Strzałka Kazimierz, Gruszecki Wiesław I
Department of Biophysics, Institute of Physics, Maria Curie-Skłodowska University, Lublin, Poland.
Biochim Biophys Acta. 2005 Jun 15;1712(1):17-28. doi: 10.1016/j.bbamem.2005.03.010. Epub 2005 Apr 11.
Polar carotenoid pigment - canthaxanthin - has been found to interfere with the organization of biological membranes, in particular of the retina membranes of an eye of primates. The organization of lipid membranes formed with dipalmitoylphosphatidylcholine (DPPC) and egg yolk phosphatidylcholine containing canthaxanthin was studied by means of several techniques including: electronic absorption spectroscopy, linear dichroism, X-ray diffractometry, (1)H-NMR spectroscopy and FTIR spectroscopy. It appears that canthaxanthin present in the lipid membranes at relatively low concentration (below 1 mol% with respect to lipid) modifies significantly physical properties of the membranes. In particular, canthaxanthin (i) exerts restrictions to the segmental molecular motion of lipid molecules both in the headgroup region and in the hydrophobic core of the bilayer, (ii) promotes extended conformation of alkyl lipid chains, (iii) modifies the surface of the lipid membranes (in particular in the gel state, L(beta )) and promotes the aggregation of lipid vesicles. It is concluded that canthaxanthin incorporated into lipid membranes is distributed among two pools: one spanning the lipid bilayer roughly perpendicularly to the surface of the membrane and one parallel to the membrane, localized in the headgroup region. The population of the horizontal fraction increases with the increase in the concentration of the pigment in the lipid phase. Such a conclusion is supported by the linear dichroism analysis of the oriented lipid multibilayers containing canthaxanthin: The mean angle between the dipole transition moment and the axis normal to the plane of the membrane was determined as 20+/-3 degrees at 0.5 mol% and 47+/-3 degrees at 2 mol% canthaxanthin. The analysis of the absorption spectra of canthaxanthin in the lipid phase and (1)H-NMR spectra of lipids point to the exceptionally low aggregation threshold of the pigment in the membrane environment (approximately 1 mol%). All results demonstrate a very strong modifying effect of canthaxanthin with respect to the dynamic and structural properties of lipid membranes.
极地类胡萝卜素色素——角黄素——已被发现会干扰生物膜的结构，尤其是灵长类动物眼睛视网膜膜的结构。通过多种技术研究了由二棕榈酰磷脂酰胆碱（DPPC）和含角黄素的蛋黄磷脂酰胆碱形成的脂质膜的结构，这些技术包括：电子吸收光谱法、线性二色性、X射线衍射法、¹H - NMR光谱法和傅里叶变换红外光谱法。结果表明，脂质膜中相对低浓度（相对于脂质低于1摩尔%）的角黄素会显著改变膜的物理性质。特别是，角黄素（i）对脂质分子在头部基团区域和双层疏水核心中的链段分子运动施加限制，（ii）促进烷基脂质链的伸展构象，（iii）改变脂质膜的表面（特别是在凝胶态L(β)中）并促进脂质囊泡的聚集。得出的结论是，掺入脂质膜中的角黄素分布在两个池之间：一个大致垂直于膜表面跨越脂质双层，另一个平行于膜，位于头部基团区域。水平部分的数量随着脂质相中色素浓度的增加而增加。含有角黄素的取向脂质多层膜的线性二色性分析支持了这一结论：在角黄素含量为0.5摩尔%时，偶极跃迁矩与垂直于膜平面的轴之间的平均角度确定为20±3度，在角黄素含量为2摩尔%时为47±3度。脂质相中角黄素吸收光谱和脂质的¹H - NMR光谱分析表明，该色素在膜环境中的聚集阈值极低（约1摩尔%）。所有结果都证明了角黄素对脂质膜的动态和结构性质具有非常强的修饰作用。
