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Membrane Structure 367

(grown on a medium supplemented with specifically SEE ALSO THE FOLLOWING ARTICLES
deuterated or perdeuterated fatty acids), cardiolipin- or
glycerol-auxotroph Escherichia coli (grown in tissue- BIOENERGETICS • ELECTRON TRANSFER REACTIONS •
culture medium containing selectively deuterated fatty ENERGY TRANSFER,INTRAMOLECULAR • ION KINETICS
acids or phosphatidyl glycerol), and mouse fibrob- AND ENERGETICS • ION TRANSPORT ACROSS BIO-
last L-M cells (grown in tissue-culture medium con- LOGICAL MEMBRANES • LIPOPROTEIN/CHOLESTEROL
taining selectively deuterated choline or ethanolamine). METABOLISM • PROTEIN SYNTHESIS
The membranes of these systems showed very simi-
lar fatty acid and headgroup motion, ordering, and ori-
entation as the membranes formed from the extracted BIBLIOGRAPHY
lipids without protein. No long-lived lipid–protein com-
plexes were observed for neutral or negatively charged Davis, J. H. (1983). “The description of membrane lipid conformation,
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VII. CONCLUDING REMARKS
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Divecha, N., Clarke, J. H., Roefs, M., Halstead, J. R., and D’Santos, C.
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tional biological membranes are in the liquid crystal- Life Sci. 57, 379–393.
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the phosphatidylcholines,” Biochim. Biophys. Acta 1376, 91–145.
talline phase are essentially carried over into the liquid
Mitchell, D. C., Gawrisch, K., Litman, B. J., and Salem, N., Jr. (1998).
crystalline state. An order parameter profile comparable “Why is docosahexaenoic acid essential for nervous system function?”
for the most diverse membranes has been established. Biochem. Soc. Trans. 26, 365–370.
The absolute values of order parameters may, however, Muniz, M., and Riezman, H. (2000). “Intracellular transport of GPI-
vary as much as a factor of two as a consequence of the anchored proteins,” Embo J. 19, 10–15.
Op den Kamp, J. A. F., Roelofsen, B., and van Deenen, L. L. M. (1985).
large variation in lipid composition encountered in bio-
“Structural dynamic aspects of phsophatidylcholine in the human ery-
logical membranes. Membrane ordering decreases upon throcyte membrane,” Trends Biochem. Sci. 10, 320–323.
increasing the temperature, introducing one or several Seelig,J.(1977).“Deuteriummagneticresonance:theoryandapplication
cis-double bonds into a saturated fatty acyl chain, or to lipid membranes,” Q. Rev. Biophys. 10, 353–418.
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2
upon adding an amphiphilic guest molecule. In contrast, Seelig, J. (1978). “[ H]Hydrogen and [ P]phosphorus nuclear-
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terol. Transmembrane proteins barely influence the lipid Seelig, J. (1978). “ P nuclear magnetic resonance and the headgroup
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order, as they perfectly match the lipid bilayer proper- structure of phospholipids in membranes,” Biochim. Biophys. Acta
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the lipid packing density and hence the membrane order Seelig, J. (1993). “Phospholipid headgroups as sensors of electric
charge,” In “New Developments in Lipid–Protein Interactions and
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Receptor and Function” (K. W. A. Wirtz, ed.), Plenum Press, New
tion of membrane proteins. A conformational change in York.
a membrane protein may further be induced by an out- Seelig, J. (1995). “Metal ion interactions with lipids,” In “Handbook of
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a fast exchange of lipid molecules is observed between in biological membranes: H-NMR as a method to study structure,
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