Physical Properties of Cholesterol Bilayer Domains
Additional Funding Sources
The project described was supported by NIH Grant Nos. R01EY030067 and R01EY015526 and the Dr. Subczynski lab at the Medical College of Wisconsin Department of Biophysics.
Abstract
Continuous-wave electron paramagnetic resonance (EPR) spin-labeling methods were used to study the physical properties of cholesterol bilayer domains (CBDs) in Chol/POPC (cholesterol/1-palmitoyl-2-oleoylphosphatidylcholine) membranes. Physical properties include maximum splitting mobility parameter and hydrophobicity. The Chol/POPC mixing ratio was varied from 0 to 3. Chol content corresponding to the minimum values of the mobility parameters was used to determine the initial point of CBDs formation. The minimum mobility was observed at Chol/POPC mixing ratio of 1 and 1.25 using ASL and CSL spin labels respectively and the CBDs start to form above this Chol/POPC mixing ratio. Spectral subtraction was performed between the regions where phospholipid cholesterol domain (PCD) coexist with CBDs to the regions where only PCD is formed to estimate the mobility parameter maximum splitting and hydrophobicity of CBDs. We found that the mobility parameter for CBDs is higher than that of PCD indicating higher dynamics of CBDs in comparison to PCD. The maximum splitting for CBDs is slightly higher than that of PCDs indicting that CBDs are more ordered in comparison to PCDs. Hydrophobicity for CBDs is lower in comparison to PCD indicating that water penetration in CBDs regions is higher in comparison to PCDs.
Physical Properties of Cholesterol Bilayer Domains
Continuous-wave electron paramagnetic resonance (EPR) spin-labeling methods were used to study the physical properties of cholesterol bilayer domains (CBDs) in Chol/POPC (cholesterol/1-palmitoyl-2-oleoylphosphatidylcholine) membranes. Physical properties include maximum splitting mobility parameter and hydrophobicity. The Chol/POPC mixing ratio was varied from 0 to 3. Chol content corresponding to the minimum values of the mobility parameters was used to determine the initial point of CBDs formation. The minimum mobility was observed at Chol/POPC mixing ratio of 1 and 1.25 using ASL and CSL spin labels respectively and the CBDs start to form above this Chol/POPC mixing ratio. Spectral subtraction was performed between the regions where phospholipid cholesterol domain (PCD) coexist with CBDs to the regions where only PCD is formed to estimate the mobility parameter maximum splitting and hydrophobicity of CBDs. We found that the mobility parameter for CBDs is higher than that of PCD indicating higher dynamics of CBDs in comparison to PCD. The maximum splitting for CBDs is slightly higher than that of PCDs indicting that CBDs are more ordered in comparison to PCDs. Hydrophobicity for CBDs is lower in comparison to PCD indicating that water penetration in CBDs regions is higher in comparison to PCDs.