Interaction Of Synthetic Pigments With Cellular Membrane

Sudan red compounds(â… ,â…¡,â…¢,â…£)are hydrophobic compounds,but in contrast to hydrocarbons,Sudan red compounds contain azo and hydroxy groups, which can form hydrogen bonds with the polar headgroups of membrane phospholipids.Thus,entry may be impeded.They could have different toxicities from other lipophilic hydrocarbons.In this paper liposome is used to investigate the interaction between simulation lipid membrane and Sudan red compounds.The results reveal that Sudan dyes correspond to the Langmuir adsorption isotherm which has been set up for many years.The binding number of Sudan red compounds were calculated in liposomes.Effects of electrolyte,temperature,acidity of solution are detected to analyze the possible mechanism of interaction by their molecular structure. Aggregation of Sudan red and living Escherichia coli(E.coli)was analysised with in vitro experiments,which are to confirm the theoretic suppose that Sudan dyes accumulated only on the cell membrane surface according to the monolayer adsorption because of containing the hydrogen-bond.They could not diffuse into cytoplasm or lead to target toxicity also.The two kinds of ionic organic compounds,anionic diamine blue 3R(DAB)and cationic rhodamine B(RB),were chosen to be investigated the bondings with lecithin liposomes and E.coli.The interactions corresponded to the Langmuir and Temkin adsorption isotherm in only monolayer.The influence of ionic strength,pH and temperature on the adsorption was carried out.The binding force,type and sites of DAB and RB were analyzed and discussed.The results have showed that the chemical adsorption of DAB and RB on the liposomes and cell is strong,exothermal and idiopathic,which contained the union of non-covalent bonds,such as electrostatic bond,hydrogen bond and van der Waals force.Moreover,most of DAB and RB were accumulated on the excellular membrane and wall,hardly to entry into cytoplasm. Besides,the competitive absorption was found when both DAB and RB existed simultaneously in a liposome or cell liquid.The hydrophobic polar organics(Sudan red)and the hydrophobic polar organics (DAB,RB)were adsorbed on pericellular membrane by hydrogen bond.The adsorptive capacity was related with molecular structure and the amount of electron charge.The difference is the hydrophobic polar organics were adsorbed by ionic bond in addition.The results provided a very useful experimental strategy for the quantitative assessment of membrane toxicity of aromatic hydrocarbon and recognition of the terminal toxic substances.