Mechanical Properties of the Model of Pig Lens Lipid Membrane
Additional Funding Sources
This work was supported by Grant No. R01 EY030067 from the National Institutes of Health, USA.
Abstract
The pig lens membrane is primarily composed of four different phospholipids (PLs): phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and sphingomyelin, with phosphatidylcholine being the most abundant. Cholesterol is an important sterol found in the pig lens membrane where the cholesterol to phospholipid ratio (Chol/PL) is ~1 and ~2 in the cortical and nuclear membrane, respectively. We studied the mechanical properties of a model pig lens membrane with a Chol/PL mixing ratio of 0 and 1 using atomic force microscopy (AFM). We found that the supported pig lens model membrane of Chol/PL ratio 0 displayed two phases: solid ordered phase (so) and liquid disordered phase (ld); the height difference between these two phases was approximately 1 nm. The membrane of Chol/PL mixing ratio 1 had only one phase, liquid ordered phase (lo). We obtained two different breakthrough forces for the membrane of Chol/PL mixing ratio of 0 with an average value of 15.49±2.8 nN and 4.83±0.31 nN, related to so and ld, respectively. The membrane of Chol/PL mixing ratio 1 with only one phase, lo, had an average break through force of 10.62±0.39 nN. The elasticity of the membrane, quantified by the area compressibility modulus (KA), of the membrane with Chol/PL mixing ratio 1 was obtained as 1060±230 mN/m.
Mechanical Properties of the Model of Pig Lens Lipid Membrane
The pig lens membrane is primarily composed of four different phospholipids (PLs): phosphatidylcholine, phosphatidylserine, phosphatidylethanolamine, and sphingomyelin, with phosphatidylcholine being the most abundant. Cholesterol is an important sterol found in the pig lens membrane where the cholesterol to phospholipid ratio (Chol/PL) is ~1 and ~2 in the cortical and nuclear membrane, respectively. We studied the mechanical properties of a model pig lens membrane with a Chol/PL mixing ratio of 0 and 1 using atomic force microscopy (AFM). We found that the supported pig lens model membrane of Chol/PL ratio 0 displayed two phases: solid ordered phase (so) and liquid disordered phase (ld); the height difference between these two phases was approximately 1 nm. The membrane of Chol/PL mixing ratio 1 had only one phase, liquid ordered phase (lo). We obtained two different breakthrough forces for the membrane of Chol/PL mixing ratio of 0 with an average value of 15.49±2.8 nN and 4.83±0.31 nN, related to so and ld, respectively. The membrane of Chol/PL mixing ratio 1 with only one phase, lo, had an average break through force of 10.62±0.39 nN. The elasticity of the membrane, quantified by the area compressibility modulus (KA), of the membrane with Chol/PL mixing ratio 1 was obtained as 1060±230 mN/m.