The authors applied click chemistry to previously inaccessible biologic
environments. Towards that end, they used a modified azide and clicking it onto an alkyne but without using copper ions which are toxic to cells, they invent a reaction between azides and alkynes that reacts in a vigorous manner and totally without the help of copper. With this they invent a copper free click reaction called the “strain-promoted alkyne-azide cycloaddition’ or the ‘SPAAC’ reaction. By adding fluorophores (see Green Fluorescent Protein GM- 13564) to the reaction platform, they could
illuminate glycans in the cell surface and the emerging glycome of the zebrafish.

Order of authorship in the original publication: Laughlin, Baskin, et al, Bertozzi.

(Thanks to Juan Weiss for this reference and its interpretation.)