Rapid Macrocycle Threading by a Fluorescent Dye-Polymer Conjugate in Water with Nanomolar Affinity

Evan M. Peck, Wenqi Liu, Graeme T. Spence, Scott K. Shaw, Anthony P. Davis*, Harry Destecroix, Bradley D. Smith

*Corresponding author for this work

Research output: Contribution to journalArticle (Academic Journal)peer-review

58 Citations (Scopus)


A macrocyclic tetralactam host is threaded by a highly fluorescent squaraine dye that is flanked by two polyethylene glycol (PEG) chains with nanomolar dissociation constants in water. Furthermore, the rates of bimolecular association are very fast with k<inf>on</inf> ≤ 10<sup>6</sup>-10<sup>7</sup> M<sup>-1</sup> s<sup>-1</sup>. The association is effective under cell culture conditions and produces large changes in dye optical properties including turn-on near-infrared fluorescence that can be imaged using cell microscopy. Association constants in water are ∼1000 times higher than those in organic solvents and strongly enthalpically favored at 27 °C. The threading rate is hardly affected by the length of the PEG chains that flank the squaraine dye. For example, macrocycle threading by a dye conjugate with two appended PEG2000 chains is only three times slower than threading by a conjugate with triethylene glycol chains that are 20 times shorter. The results are a promising advance toward synthetic mimics of streptavidin/biotin.

Original languageEnglish
Pages (from-to)8668-8671
Number of pages4
JournalJournal of the American Chemical Society
Issue number27
Publication statusPublished - 15 Jul 2015


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