Lipid and DNA interaction with the triorganotin dimethylaminophenylazobenzoates studied by DSC and spectroscopy methods

Abstract

The aim of the study was to investigate and compare the interaction of tributyltin (TBTA) and triphenyltin (TPhTA) 2-[4 (dimethylamino)phenylazo]benzoates complexes with the lipid membrane and plasmid DNA. Both TBTA and TPhTA belong to the group of promising anticancer agents. Differential scanning calorimetry method was employed to examine the heat signal associated with phase transitions of liposomes formed from dipalmitoylphosphatidylcholine (DPPC) or DPPC/cholesterol and modified with TBTA and TPhTA. The investigated compounds influence the thermotropic parameters of the DPPC and DPPC/cholesterol lipid bilayer in a slightly different way: Although the temperature of the main phase transition of the DPPC remains almost unaffected, the addition of TPhTA can abolish sub- and pre-transition when added in sufficiently high concentrations. At the same time, the addition of the TBTA practically does not change the sub-transition and only slightly influences the pre-transition. The effect of organotin compounds on plasmid DNA was investigated using single-molecule florescence technique and time-correlated single-photon counting fluorescence correlation spectroscopy. Influence of TBTA and TPhTA on DNA resulted only in fractional conformation change which did not lead to the tightly packed conformation however, analysis of the diffusion times indicates that TPhTA interacts with DNA in a different mode than TBTA.