ADRIAMYCIN AND DAUNOMYCIN SEMIQUINONE MEMBRANE BUFFER PARTITION CONSTANTS USING THE SPIN-BROADENING TECHNIQUE/

Membrane/buffer partition constants have been determined for the semiq uinones of adriamycin, Adrsq, and daunomycin, Daunosq, as a function o f ionic strength and cholesterol content in phosphatidylcholine multil amellar vesicles using the spin-broadening technique. The partition co nstants corresponding to Adrsq were essentially similar to those of Da unosq under any of the conditions studied, These constants increase wi th ionic strength increase and decrease with an increase in cholestero l concentration at the membrane. These observations could have implica tions in the Adr and Dauno cytotoxicities where their corresponding se miquinones are postulated as important intermediates and consequently their interactions with biological membranes should also be considered as important. (C) 1997 Academic Press.