Abstract
The metachromatic shifts of dye ions were briefly reviewed. The three possible explanations for the shifts were described.
1) Aggregation of dye ions at binding site.
2) Electrostatic interactions between dye ion and ionic side chains.
3) Dispersive interactions between dye ion and apolar side chains.
Initially, the findings on acridine dye-DNA complexes were discussed from 1). Next, the blue shift observed in methyl orange binding to bovine serum albumin was discussed on the basis of the explanations 2) and 3). Them, it was concluded that the shift due to the disruption of hydrogen bonds plays an important role in exhibiting the blue shift.
Finally, the theoretical calculations about the spectral shift which demonstrate how the results may be applied to metachromasy were described.
