Biopolymers and cell. 2000; 16 (5): 345 - 355

Interaction of cyanine dyes with nucleic acids. 14. Spectral peculiarities of several monomethyne benzothiazole cyanine dyes and their interaction with DNA

T. Yu. Ogul'chansky, V. M. Yashchuk, S. M. Yarmoluk, M, Yu. Losytskyy

Absorption, fluorescence emission and excitation spectra of solutions of monomethyne benzothiazole cyanine dyes — thiazole orange (TO), Cyan 40 and Cyan 13 — have been studied in a wide concentration range in the presence and without DNA. It has been established that both molecular and aggregate absorption as well as both molecular and aggregate fluorescence are observed for the solutions of the dyes investigated, the aggregates electron system being essentially transformed after photon absorption. It has been shown that the own fluorescence of dye molecules dominates in emission of the investigated dye solutions with DNA. Its considerable quantum yield can be explained by the dye molecule fixation on the DNA molecule. The concentration auenching of this fluorescence has been found and it is accompanied with the appearance of a new absorption band. It has been supposed that the aggregates consisting of dye molecules fixed on DNA and free dye molecules are formed. On the ground of the data obtained we have concluded that the dye molecules interact through half-intercalation mode with DNA molecules and that the model of full intercalation is inapplicable to the interaction of the dyes investigated with DNA molecules.