Observing the structural variations on binary complex vesicle surfaces and the influence on molecular transportation

A clear understanding on the structure and functionality of lipid molecules on natural or artificial cell membranes are important yet hard to be achieved. In this work we compared the adsorption and transportation of a dye molecule (D289) on the surface of 1,2-dioleoyl-sn-glycero-3-phospho-rac-(1-glycerol) sodium salt (DOPG) and 10, 12-pentacosadiynoic acid (PCDA) lipid vesicles, as well as DOPG/PCDA binary complex vesicles, using in-situ second harmonic generation (SHG) technique. It was observed that the dynamics of the cross-membrane transportation of D289 varied significantly with the change in composition of the vesicle membrane. For vesicles prepared with a fixed PCDA/DOPG ratio, the experiments showed notable variations in the SHG curves obtained with vesicles prepared at different batches. The molecular domains formed on the surface of the binary complex vesicles are the most possible explanation to this experimental observation. Two possible cross-membrane transportation mechanisms are presented according to the observed cross-membrane dynamic parameters.