Sugar-induced color and orientation changes in a cyanine dye bound to boronic -acid-appended poly(L-lysine)

A cyanine dye (2) can be orientated on boronic-acid-modified poly(L- and D-lysine)s (L- and D-1, respectively) in the presence of saccharides. The main driving-force for the association is the electrostatic attraction between cationic 2 and the anionic center developed by complexation of the boronic acid residue with saccharides. The chiral orientation can be monitored by a CD spectroscopic method: it is mainly governed by the chirality of 1 but not by the chirality of saccharides. This is a novel system to control the dye orientation which occurs owing to the cooperative action of both naturally-originated α-amino acids and saccharides.