Rate of tetracycline photolysis during irradiation at 365 nm.

Kinetics of photolysis of the antibiotic tetracycline (TC) during irradiation at 365 nm was studied in three buffer solutions usually used for studies on TC binding to its main cell targets--a transcriptional repressor protein TetR and to the ribosome. These buffer solutions contain magnesium ions and an antioxidant--mercaptoethanol or dithiothreitol. The rate of TC photolysis was maximal in medium which contained 14 mM mercaptoethanol and 5 mM magnesium ions. In the absence of mercaptoethanol the photolysis rate was more than twofold decreased. The rate constants and quantum yields of the photolysis were determined under various conditions.