Spontaneous Organization of Amphotericin B in Aqueous Medium

Abstract

Spectral effects accompanying the spontaneous organization of Amphotericin B (AmB) in aqueous medium and in the presence of some surfactants are analyzed in terms of the exciton splitting theory. The appearance of both bathochromic and hypsochromic shifts is an indication that two kinds of molecular interactions are present in the aggregates, representing "card pack" and "head-to-tail" patterns. The latter has been interpreted as an effect of the dimerization along the long molecular axes of AmB, whereas the former one is the effect of interactions between molecules forming hydrophobic pores. The value of a hypsochromic spectral shift of 4368 cm -1 makes it possible to find the number of 5 AmB molecules working as units to form a single pore. In the presence of n-propanol or some surfactants, another molecular arrangement in the aggregated species is observed. In this arrangement, the distances between chromophores are smaller than in the previous one. Physiological consequences of such a spontaneous molecular organization of the drug are discussed.