ja5b03573_si_001.pdf (9.31 MB)
Rapid Macrocycle Threading by a Fluorescent Dye–Polymer Conjugate in Water with Nanomolar Affinity
journal contribution
posted on 2015-12-17, 08:40 authored by Evan M. Peck, Wenqi Liu, Graeme
T. Spence, Scott K. Shaw, Anthony P. Davis, Harry Destecroix, Bradley D. SmithA 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 kon ≈ 106–107 M–1 s–1. 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.