Abstract
We report the utilization of magnetically aligned phospholipid bilayers (bicelles) to study the effects of cholesterol in phospholipid bilayers for both chain perdeuterated DMPC and partially deuterated α-[2,2,3,4,4,6- d6]-cholesterol using 2H solid-state NMR spectroscopy. The quadrupolar splittings at 40̊C were 25.5 and 37.7 kHz, respectively, for the 2,4-2Heq and 2,4-2Hax deuterons when the bilayer normal of the discs was aligned perpendicular to the static magnetic field. The quadrupolar splittings were doubled when Yb 3+ ions were added to flip the bicelles 90° such that the bilayer normal was colinear with the magnetic field. The results suggest that cholesterol is incorporated into the bicelle discs. For chain perdeuterated DMPC-d54, incorporated into DMPC-DHPC bicelle discs, the individual quadrupolar splittings of the methylene and methyl groups doubled on going from the perpendicular to the parallel alignment. Also, the presence of cholesterol increased the overall ordering of the acyl chains of the phospholipids. S CDi calculations were extracted directly from the 2H quadrupolar splittings of the chain perdeuterated DMPC. The order parameter, SCDi, calculations clearly indicated an overall degree of ordering of the acyl chains in the presence of cholesterol. We also noted a disordering effect at higher temperatures. This study demonstrates the ease with which 2H order parameters can be calculated utilizing magnetically aligned phospholipid bilayers when compared with randomly dispersed membrane samples.
Original language | English |
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Pages (from-to) | 132-138 |
Number of pages | 7 |
Journal | Magnetic Resonance in Chemistry |
Volume | 42 |
Issue number | 2 |
DOIs | |
Publication status | Published - Feb 2004 |
Externally published | Yes |
Keywords
- Acyl chain dynamics
- Bicelles
- Cholesterol
- H NMR
- NMR
- Phospholipid bilayers
- Solid-state NMR