Li, J. et al. J. Am. Chem. Soc. 140, 16589–16595 (2018).

Advances in mass spectrometry have helped scientists detect protein glycosylation in vitro; however, such approaches have practical limitations for in vivo applications. Meanwhile, fluorescent proteins have been used to monitor glycosylation in a protein-specific manner, but this approach lacks sensitivity. To enhance sensitivity, Li et al. use an amplification approach that relies on a proximity-induced hybridization chain reaction (HCR). The approach includes two DNA probes that either attach to glycans or recognize target proteins. The latter consists of an aptamer domain for protein recognition, as well as a spacer domain and initiator domain to trigger HCR. When both probes are bound, HCR occurs, resulting in an amplified fluorescent signal. The researchers apply this method to visualize tyrosine-protein-kinase-specific sialic acid states on CCRF-CEM cell surfaces. They also visualized glycosylation in zebrafish larvae that were injected with CCRF-CEM cells.