Cholesterol is both an important structural component of cell membranes and an early intermediate in hormone and bile acid biosynthesis. The localization and measurement of cholesterol in cells is therefore of great interest. Filipin is the collective name given to four isomeric polyene macrolides isolated from cultures of S. filipinensis; Filipin III is the predominant isomer and the one used in most studies. Filipin binds to cholesterol in membranes, forming ultrastructural aggregates and complexes which can be visualized by freeze-fracture electron microscopy.[1],[2] The binding of cholesterol also decreases the intrinsic fluorescence of Filipin, and this property has also been used to detect cholesterol in membrane fractions.[3]
Reference:
[1]. Castanho, M.A., Coutinho, A., and Prieto, M.J. Absorption and fluorescence spectra of polyene antibiotics in the presence of cholesterol J. Biol. Chem. 267(1), 204-209 (1992).
[2]. Miller, R.G. Mini Review. The use and abuse of filipin to localize cholesterol in membranes Cell Biol. Int. Rep. 8(7), 519-535 (1984).
[3]. Severs, N.J., and Robenek, H. Detection of microdomains in biomembranes. An appraisal of recent developments in freeze-fracture cytochemistry Biochimica et Biophysica Acta 737, 373-408 (1983)
胆固醇既是细胞膜的重要结构成分，也是激素和胆汁酸生物合成的早期中间体。因此，在细胞中定位和测量胆固醇非常重要。菲洛平（Filipin）是从S. filipinensis培养物中分离出来的四种同分异构体多烯大环内酯的集合名称；菲洛平III是主要同分异构体，也是大多数研究所使用的一种。菲洛平与膜中的胆固醇结合，形成超微结构聚集体和复合物，可以通过冷冻切片电子显微镜观察到[1] [2]。 胆固醇的结合还会降低菲洛平本身荧光强度，并且这个特性也被用于检测薄膜部分中的胆固醇[3]。