Lateral diffusion coefficients of separate lipid species in a ternary raft-forming bilayer: A Pfg-NMR multinuclear study
atomic-force microscopy; Biophysics; cell-membranes; fluorescence correlation spectroscopy; insulin-receptor; least-squares analysis; model membranes; phase-equilibria; plasma-membrane; signal-transduction; spectral data sets
By isotopical labeling lipid lateral diffusion coefficients for each of the membrane constituents, including cholesterol, have been measured by H-1, H-2, and F-19 pulsed field gradient NMR spectroscopy in macroscopically oriented lipid bilayers. This provides a means of obtaining detailed dynamic and compositional information in raft-forming lipid bilayers without introducing foreign molecules into the systems. The raft systems studied contained dioleoylphosphatidylcholine/dipalmitoylphosphatidylcholine (DPPC)/cholesterol at the molar ratios of 42.5: 42.5: 15 and 35: 35: 30 in excess water. At temperatures below 30 degrees C the raft system forms large (>1 mu m) domains of a liquid ordered (l(o)) phase, in which the lipid lateral diffusion was; 5 times slower than for the lipids in the surrounding liquid disordered (l(d)) phase. Within each domain all lipid species showed the same diffusion coefficient, despite the very different structures of cholesterol and phospholipids. DPPC partitions exclusively into the l(o) domains, whereas cholesterol and dioleoylphosphatidylcholine were distributed in both l(o) and l(d) phases. The cholesterol concentration was found to be 10-20 mol% in the l(d) domain and 30-40 mol% in the l(o) domain. Comparison of these results with data from sphingomyelin-containing systems suggests that DPPC interacts more weakly with cholesterol than does sphingomyelin.
Oradd G; Westerman P W; Lindblom G
Biophysical Journal
2005
2005-07
Journal Article
<a href="http://doi.org/10.1529/biophysj.105.061762" target="_blank" rel="noreferrer noopener">10.1529/biophysj.105.061762</a>
Lateral diffusion of cholesterol and dimyristoylphosphatidylcholine in a lipid bilayer measured by pulsed field gradient NMR spectroscopy
Biophysics; caveolae; insulin-receptor; membranes; nuclear magnetic-resonance
The pulsed field gradient NMR method for measuring self-diffusion has been used for a direct determination of the lateral diffusion coefficient of cholesterol, fluorine labeled at the 6-position, for an oriented lamellar liquid-crystalline phase of dimyristoylphosphatidylcholine (DMPC)/cholesterol/water. It is found that the diffusion coefficients of DMPC and cholesterol are equal over a large temperature interval. The apparent energy of activation for the diffusion process (58 kJ/mol) is about the same as for a lamellar phase of DMPC/water, whereas the phospholipid lateral diffusion coefficient is approximately four times smaller in the presence of cholesterol.
Oradd G; Lindblom G; Westerman P W
Biophysical Journal
2002
2002-11
Journal Article
<a href="http://doi.org/10.1016/s0006-3495(02)75279-x" target="_blank" rel="noreferrer noopener">10.1016/s0006-3495(02)75279-x</a>