1 research outputs found
Rapid Macrocycle Threading by a Fluorescent Dye–Polymer Conjugate in Water with Nanomolar Affinity
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 <i>k</i><sub>on</sub> ≈ 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