(a) UV-visible absorption spectra of dye 6 (10 μM) in different pH solutions (pH 7.0, 10.0, 10.5, 11.0, 11.5, 12.0, 12.5 and 13.0), measured in a methanol/water mixture (1/1, v/v) containing 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid (HEPES, 5.0 mM); (b) the UV-visible absorption spectra of dye 6 (10 μM) in the presence and absence of D-fructose (0, 1, 2, 5, 10, 20, 50 and 100 mM), measured in a methanol/water mixture (1/1, v/v) containing N-cyclohexyl-2-aminoethanesulfonic acid (CHES, 5.0 mM), pH 10.0. Reprinted with permission from [66]. Copyright 2010 The Chemical Society of Japan.