Department of Neuroscience, University of Pisa, Via Roma 55, Pisa 56100, Italy.
Biochem Soc Trans. 2013 Feb 1;41(1):191-6. doi: 10.1042/BST20120250.
The possibility to visualize and image the arrangement of proteins within the cell at the molecular level has always been an attraction for scientists in biological research. In particular, for signalling molecules such as GPCRs (G-protein-coupled receptors), the existence of protein aggregates such as oligomers or clusters has been the topic of extensive debate. One of the reasons for this lively argument is that the molecular size is below the diffraction-limited resolution of the conventional microscopy, precluding the direct visualization of protein super-structures. On the other hand, new super-resolution microscopy techniques, such as the PALM (photoactivated localization microscopy), allow the limit of the resolution power of conventional optics to be broken and the localization of single molecules to be determined with a precision of 10-20 nm, close to their molecular size. The application of super-resolution microscopy to study the spatial and temporal organization of GPCRs has brought new insights into receptor arrangement on the plasma membrane. Furthermore, the use of this powerful microscopy technique as a quantitative tool opens up the possibility for investigating and quantifying the number of molecules in biological assemblies and determining the protein stoichiometry in signalling complexes.
在分子水平上可视化和成像细胞内蛋白质排列的可能性一直吸引着生物研究领域的科学家。特别是对于信号分子如 GPCR（G 蛋白偶联受体），蛋白质聚集体（如寡聚体或簇）的存在一直是广泛争论的话题。产生这种激烈争论的原因之一是，分子尺寸低于传统显微镜的衍射极限分辨率，无法直接观察蛋白质超结构。另一方面，新的超分辨率显微镜技术，如 PALM（光激活定位显微镜），可以突破传统光学分辨率的限制，以 10-20nm 的精度确定单分子的定位，接近其分子大小。将超分辨率显微镜应用于研究 GPCR 的空间和时间组织，为受体在质膜上的排列提供了新的见解。此外，将这种强大的显微镜技术用作定量工具，为研究和量化生物组装体中的分子数量以及确定信号复合物中的蛋白质化学计量学提供了可能性。
