Regulated ensembles and lipid membranes*

Cellular membranes are composed of lipid bilayers, amphiphilic molecules with polar headgroups and hydrophobic tails. Their composition is highly complex, involving hundreds of different lipid types and the regulation mechanism is still the subject of intense research. A recent experiment [1] has shown that cholesterol concentration increases with temperature in zebrafishes, as well as the demixing temperature, two results which appear to be contradictory results since cholesterol promotes mixing. Here, we show that many aspects of the zebrafish experiments can be replicated if one assumes a chemical reaction network for regulation of acyl tails. Effectively, this would mean that acyl tail saturation is loosely regulated by cells and mainly directed by cholesterol fraction. This view also explains trends seen along the secretory pathway between cholesterol concentration and acyl tail saturation.

[1] M. Burns, K. Wisser, J. Wu, I. Levental, S. L. Veatch, ”Miscibility transition temperature scales with growth temperature in a zebrafish cell line” Biophysical Journal 113 (2017)