The Limitations of Chlorotetracycline as a Fluorescent Probe of Divalent Cations Associated with Membranes

Abstract

The interaction of chlortetracycline with Mg Cl2, detergents and ATP and ADP was investigated. At various pH the fluorescence of chlortetracycline, or the chlortetracycline complex, is enhanced in the presence of the negatively charged detergent sodium dodecyl sulfate, the uncharged detergent Triton X 100, or the positively charged detergent cetyltrimethylammonium bromide. A ternary fluorescent complex is formed between chlortetracycline, Mg and ATP, or ADP. In a biological membrane it would not seem possible to distinguish between the fluorescence signal arising from chlortetracycline acting as a probe of divalent cations bound to specific sites on the membrane and that arising from the complex of chlortetracycline with divalent cations acting as a probe of neutral or negative regions of the membrane.