Yuan C, Johnston L J
Steacie Institute for Molecular Sciences, National Research Council Canada, Ottawa, ON K1A 0R6 Canada.
J Microsc. 2002 Feb;205(Pt 2):136-46. doi: 10.1046/j.0022-2720.2001.00982.x.
A combination of atomic force microscopy (AFM) and near field scanning optical microscopy has been used to study domain formation in dipalmitoylphosphatidylcholine (DPPC)/cholesterol monolayers with cholesterol concentrations ranging from 0 to 50%. The results show a clear evolution from a mixture of liquid expanded and liquid condensed phases for cholesterol concentrations < 10% to a mixture of liquid expanded and two cholesterol-containing phases at intermediate concentrations, and finally to a single homogeneous liquid ordered phase for 33% cholesterol. Mixtures of the various phases are clearly identified by height differences in AFM and in some cases by fluorescence imaging for samples containing 0.5% BODIPY dye, which localizes preferentially in the more fluid phase. Note that fluorescence imaging, at least with the dye used here, is unable to distinguish between the cholesterol-rich and cholesterol-poor phases detected at intermediate cholesterol concentrations. The combination of fluorescence and AFM imaging provides a more complete picture of the phase evolution for cholesterol/DPPC monolayers than could be obtained by either technique alone, and presents substantial advantages over conventional fluorescence microscopy in that submicrometre-sized domains can be readily detected.
原子力显微镜（AFM）和近场扫描光学显微镜相结合，用于研究二棕榈酰磷脂酰胆碱（DPPC）/胆固醇单层膜中胆固醇浓度范围为0至50%时的畴形成。结果表明，对于胆固醇浓度<10%的情况，从液态扩张相和液态凝聚相的混合物到中间浓度下液态扩张相和两个含胆固醇相的混合物，有明显的演变，最终对于33%的胆固醇，形成单一均匀的液态有序相。通过AFM中的高度差异，在某些情况下，对于含有0.5%BODIPY染料的样品通过荧光成像，可以清楚地识别不同相的混合物，该染料优先定位于流动性更强的相中。注意，至少使用此处所用的染料进行荧光成像，无法区分在中间胆固醇浓度下检测到的富含胆固醇和贫胆固醇的相。荧光和AFM成像相结合，比单独使用任何一种技术都能更完整地呈现胆固醇/DPPC单层膜的相演变情况，并且与传统荧光显微镜相比具有显著优势，因为可以很容易地检测到亚微米尺寸的畴。
