Preferential binding as a driving mechanism of lipid domains formation

Lipid membranes are uniquely complex biological structures with large and still undisclosed regulatory potential in many living processes caused by versatile changes in their structure while adsorption of various guest molecules (dopants). This work is devoted to exploring spontaneous dopant-driven formation of lipid domains in a monolipid membrane observed experimentally for dopants with bimodal adsorption. The work offers the results obtained for a wide range of different cases exploiting our proposed original simulation method and numerical model. The central idea of the approach is dopant binding ‘like the surroundings’, i.e. preferential binding.

The value range of the preferential binding extent was determined, where stable domains are formed and their size distribution becomes steady. The density of domain size distribution is power-law, i.e. the domain patterns possesses self-similarity. Outside this range, only one phase dominates if the extent is too large, whereas if it is too small, great dispersion of membrane was observed, so the membrane is physically homogeneous. Various neighboring as well as different methods of calculation of dopant binding probabilities are considered. The results obtained differed quantitatively but not qualitatively. The suggested model and the domain definition are similar to those used in percolation theory. Thus, the results can be applicated to percolation problems.

Grounding on analysis of literature data on domain patterns formed in various lipid systems, we suggested that the preferential binding mechanism is in line with the mechanism of preferential neighboring which is implicitly assumed in such systems irrespective of their specific nature.