Understanding movement of Cholesterol in membrane by measuring the compressibility constant

The objective of the research is to understand the lipid structures in membrane. Phosphatidylserine is the most abundant negatively charged phospholipid in eukaryotic cells comprising about 10{\%} of the total phospholipids. It is highly enriched in the plasma membrane where much of the cellular inventory of cholesterol partitions. Indeed, how the spatial distribution of cholesterol in the plasma membrane and the nature of its embedding lipidic environment impact cholesterol's ability to desorb/absorb from/into the membrane has not been fully elucidated. We investigate the movement of Cholesterol in two specific lipid membranes by first understanding the characteristics of these membranes, specifically the compressibility of the membranes. Compressibility of phosphatidylserine (POPS) membrane and phosphatidylcholine (POPC) were measured using the Langmuir--Blodgett trough by compressing a monolayer of lipid. Understanding the how compressible a membrane is could potentially explain how the cholesterol moves in these membranes. A higher rigidity could reduce or slow the movement and permeability could fasten the movement of cholesterol. This could then lead to the understanding of distribution of cholesterol in plasma membrane.