Click-free imaging of carbohydrate trafficking in live cells using an azido photothermal probe
Qing Xia, Harini A. Perera, Rylie Bolarinho, Zeke A. Piskulich, Zhongyue Guo, Jiaze Yin, Hongjian He, Mingsheng Li, Xiaowei Ge, Qiang Cui, Olof Ramström, Mingdi Yan, Ji‐Xin Cheng
Abstract
Real-time tracking of intracellular carbohydrates remains challenging. While click chemistry allows bio-orthogonal tagging with fluorescent probes, the reaction permanently alters the target molecule and only allows a single snapshot. Here, we demonstrate click-free mid-infrared photothermal (MIP) imaging of azide-tagged carbohydrates in live cells. Leveraging the micromolar detection sensitivity for 6-azido-trehalose (TreAz) and the 300-nm spatial resolution of MIP imaging, the trehalose recycling pathway in single mycobacteria, from cytoplasmic uptake to membrane localization, is directly visualized. A peak shift of azide in MIP spectrum further uncovers interactions between TreAz and intracellular protein. MIP mapping of unreacted azide after click reaction reveals click chemistry heterogeneity within a bacterium. Broader applications of azido photothermal probes to visualize the initial steps of the Leloir pathway in yeasts and the newly synthesized glycans in mammalian cells are demonstrated.