Table 1.

Labeling efficiency of various bioorthogonal probes with chondroitin sulfate decasaccharide.

Probe	Labeling efficiency
azidoaniline	+++
azido -PEG3-oxyamine	++
tetrazine-oxyamine	++/+++*
tetrazine-amine	+
dibenzylcyclooctyne-amine	+
bicyclononyne-PEG3-amine (endo)	+
trans-cyclooctene -PEG3-amine	+
trans-cyclooctene-amine	+

+++: nearly complete; ++: good (about half or more); +: moderate.

*labeling is better without reduction by NaCNBH₃.

Labeling was performed using 0.1 M probe in 100 mM NaAc/150 mM NaCl, pH 5.4. After 15 min at ambient temperature, an equal volume of 1 M NaCNBH₃ was added and incubation proceeded for another 4½ h at 45 °C.