POLY-ELECTROLYTE EFFECTS ON THE CHARGE-TRANSFER COMPLEX-FORMATION BETWEEN FMN AND INDOLE-DERIVATIVES

In the reported experiments, the complex formation of flavin mononucleotide (FMN) with tryptamine, indoleacetate, and tryptophan was investigated in the presence of polyelectrolytes; that is, sodium polyethylene sulfonate (NaPES), sodium polystyrene sulfonate (NaPSS), and a copolymer of diethyldiallylammonium chloride and sulfur dioxide (DECS). The complexation of FMN and tryptamine was strongly retarded by the macrocations and macroanions, whereas that of FMN and indoleacetate was enhanced by the macrocations. Furthermore, the equilibrium constants of FMN-tryptophan complex were insensitive to the addition of polyelectrolytes. These results suggest that the complexation of FMN was strongly influenced by the electrostatic interactions between the reactant ions and macroions, in addition to those between the reactant ions, in comformity with the secondary salt effect.