活细胞荧光成像的新型标记法及其在STED中的应用（五）
SNAP-tag技术在STED超高分辨率显微成像中的应用
近十年中，显微成像技术得到了飞跃的发展，填补光学显微镜（~200 nm）到电子显微镜（~0.1 nm）分辨率缺口，打破光学衍射极限的超高分辨率显微镜也越来越趋于成熟化。其中，德国马普研究所的Stefan Hell教授凭借其研发的受激发射损耗（Stimulatedemission depletion，STED）技术荣获2014年的诺贝尔化学奖。STED超高分辨率显微镜是架构在共聚焦显微镜上，因此其成像速度非常快，可以广泛的应用于活细胞的超高分辨率成像。除了传统的YFP等荧光蛋白可以用于STED活细胞超高分辨率成像，SNAP-tag和CLIP-tag可以非常简便的的将AlexaFluo等有机染料引入活细胞，实现活细胞中多色超高分辨率成像。有机染料具有更好的光稳定性，光谱的选择也更加灵活，配合SNAP-tag和CLIP-tag标记的特异性和稳定性，可以更优秀的服务于长时间的活细胞超高分辨率显微成像。Joerg B等科学家用SNAP-tag/BG-94和CLIP-tag/BC-647分别标记了表皮生长因子受体（EGFR）和表皮生长因子（EGF）（图2），利用STED超高分辨率显微镜解析了两者在活细胞中的相互作用（图3）[12]。
图2.SNAP-tag/BG-494和CLIP-tag/BC-647N分别标记EGFR和EGF的示意图。原则上EGFR和EGF结合后会形成同源二聚体，在这里考虑到示意图的简洁清晰性，EGFR仍然以单体的形式表示。
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