Department of Physics, Chemistry and Pharmacy, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark.
Department of Biochemistry and Molecular Biology, University of Southern Denmark, Campusvej 55, 5230 Odense, Denmark.
Chem Phys Lipids. 2018 May;212:26-34. doi: 10.1016/j.chemphyslip.2017.12.005. Epub 2017 Dec 26.
Oxysterols are oxidized derivatives of cholesterol with many important biological functions. Trafficking of oxysterols in and between cells is not well studied, largely due to the lack of appropriate oxysterol analogs. Intrinsically fluorescent oxysterols present a new route towards direct observation of intracellular oxysterol trafficking by fluorescence microscopy. We characterize the fluorescence properties of the existing fluorescent 25-hydroxycholesterol analog 25-hydroxycholestatrienol, and propose a new probe with an extended conjugated system. The location of both probes inside a membrane is analyzed and compared with that of 25-hydroxycholesterol using molecular dynamics simulations. The analogs' one- and two-photon absorption properties inside the membrane are evaluated using electronic structure calculations with polarizable embedding. Due to predicted keto-enol tautomerisation of the new oxysterol analog, we also evaluate the keto form. Both analogs are found to be good probe candidates for 25-hydroxycholesterol, provided that the new analog remains in the enol-form. Only the new analog with extended conjugated system shows significant two-photon absorption, which is strongly enhanced by the presence of the membrane.
氧化固醇是胆固醇的氧化衍生物，具有许多重要的生物学功能。由于缺乏合适的氧化固醇类似物，因此细胞内外氧化固醇的运输过程还没有得到很好的研究。具有内在荧光的氧化固醇为通过荧光显微镜直接观察细胞内氧化固醇运输提供了新途径。我们对现有的荧光 25-羟胆固醇类似物 25-羟胆固醇三烯醇的荧光性质进行了表征，并提出了一种具有扩展共轭体系的新探针。利用分子动力学模拟分析了这两种探针在膜内的位置，并与 25-羟胆固醇进行了比较。利用具有极化嵌入的电子结构计算评估了这两种类似物在膜内的单光子和双光子吸收特性。由于预测新型氧化固醇类似物发生酮-烯醇互变异构，因此我们也评估了酮式。这两种类似物都可以作为 25-羟胆固醇的良好探针候选物，只要新型类似物保持烯醇形式。只有具有扩展共轭体系的新类似物显示出显著的双光子吸收，并且该吸收强烈地被膜增强。
