COMPLEXATION PROCESS IN TWO-COMPONENT CHLORTETRACYCLINE-MELANIN SOLUTIONS
The spectra and kinetics of fluorescence of two-component solutions of chlortetracycline (CHTC)-DOPA-melanin (melanin or ME) system in water have been investigated. The data obtained have been compared to the similar data for solutions of CHTC-melanosoma from the bull's eye (MB) containing natural melanins in the K-phosphatic buffer with pH = 7.4. The totality of obtained results points to the occurrence of the complexation process between molecules of chlortetracycline and melanin as they are being excited. The studies of the complexation in a solution of CHTC-MB in the buffer are complicated by the formation of a CHTC-buffer complex. In a range of 330-750 nm the effect of optical radiation on the complex CHTC-ME features a selectivity: the greatest change in its spectrum occurs when the wavelength of subjecting radiation coincides with the long-wavelength band maximum of fluorescence excitation spectrum of the CHTC-ME water solution complex. In this range, CHTC and especially melanin show a high photochemical stability. The character of a radiation effect on the objects under study in a hard ultraviolet radiation range (λ< 330 nm) differs greatly from that in a range of 330-750 nm: it is apparently accompanied by the considerable photochemical transmutations of all the system components. By comparing the characteristics of the CHTC-ME systems to those of congenial drug preparation doxycycline (DC-ME), the conclusion has been made that the chlorine atom plays a vital part in a short-wavelength band formation in a fluorescence spectrum of a CHTC-ME complex.