Interaction of natural polyamines and dimethylsilyl analogues with a phospholipid monolayer: a study by Brewster angle microscopy and PM-IRRAS

This work presents an analysis of the physicochemical interactions of natural and dimethylsilyl polyamines with an anionic deuterated phospholipid monolayer, d(62)DPPG (dipalmitoyl phosphatidyl glycerol), at the air-water interface. It was motivated by previous studies, which suggested an antitumour strategy based on the accumulation of derivatives such as bis(7-amino-4-azaheptyl) dimethylsilyl (azhepSi), in order to diminish the concentration of natural polyamines (spermine and putrescine) whose metabolism is strongly activated in tumour cells. Our results, obtained by the surface-pressure technique, Brewster angle microscopy (BAM) and polarization modulation infrared reflection absorption spectroscopy (PM-IRRAS), support the idea of an interaction between the polar head groups of d62DPPG and amino groups followed by an adsorption of polyamines up to the carbonyl group. Moreover, an insertion of the dimethylsilyl group up to the alkyl chains occurs with azhepSi, in agreement with the observation that the cohesion of the alkyl chain is lower in this case, as compared with the effect of natural polyamines. (C) 2003 Elsevier Science Ireland Ltd. All rights reserved.