Protonophoric activities of helioferin and pamamycin, lipophilic tertiary amine antibiotics from Mycogone rosea and Streptomyces aurantiacus

This paper describes the protonophoric activity of the new antibiotics helioferin and pamamycin, recently isolated lipophilic structures from the fungi Mycogone rosea and Streptomyces aurantiacus, respectively. These antibiotics display a series of interesting biological activities suggesting possible ability to interfere with fundamental cellular processes in biological membranes. Hence, this work is aimed at characterizing the effects of both antibiotics on the ion penetrability of an artificial membrane as a first approach towards the evaluation of their mode of interaction with polar bilayers. Two derivatives of pamamycin (III, IV) representing the upper half part of the molecule I were also employed in order to evaluate the influence of the molecular size and polarity on the ion penetration.