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  Chain configuration and flexibility gradient in phospholipid membranes. Comparison between spin-label electron spin resonance and deuteron nuclear magnetic resonance, and identification of new conformations.

Moser, M., Marsh, D., Meier, P., Wassmer, K. H., & Kothe, G. (1989). Chain configuration and flexibility gradient in phospholipid membranes. Comparison between spin-label electron spin resonance and deuteron nuclear magnetic resonance, and identification of new conformations. Biophysical Journal, 55(1), 111-123. doi:10.1016/S0006-3495(89)82784-5.

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Item Permalink: http://hdl.handle.net/11858/00-001M-0000-002C-84D4-6 Version Permalink: http://hdl.handle.net/11858/00-001M-0000-002C-84D8-D
Genre: Journal Article

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Moser, M., Author
Marsh, D.1, Author              
Meier, P., Author
Wassmer, K. H., Author
Kothe, G., Author
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1Department of Spectroscopy and Photochemical Kinetics, MPI for biophysical chemistry, Max Planck Society, ou_578624              

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 Abstract: The electron spin resonance spectra of 1-myristoyl-2-[n-(4,4-dimethyloxazolidine-N-oxyl)myristoyl]-sn- glycero-3-phosphocholine spin-label positional isomers (n = 6, 10, and 13) have been studied in oriented, fully hydrated bilayers of dimyristoylphosphatidylcholine, as a function of temperature and magnetic field orientation. The spectra have been simulated using a line-shape model which incorporates chain rotational isomerism, as well as restricted anisotropic motion of the lipid molecules as a whole, and which is valid in all motional regimes of conventional spin-label electron spin resonance (ESR) spectroscopy. At least one component of the lipid motion is found to lie in the slow-motion regime for all label positions, even in the fluid liquid crystalline phase, well above the phase transition. In the gel phase, the chain isomerism lies in the slow-motional regime, and the overall motions are at the rigid-limit. In the fluid phase, the chain isomerism is in the fast-motional regime, and the chain axis motions are in the slow regime. This indicates that the commonly used motional-narrowing theory is not appropriate for the interpretation of spin-label spectra in biological membranes. The simulation parameters yield a consistent description for the chain order and dynamics for all label positions. The correlation times and order parameters for the overall motion are the same at all positions down the chain, whereas the chain conformation and trans-gauche isomerism rate display a characteristic flexibility gradient, with increasing motion towards the terminal methyl end of the chain. Significantly, it is found that all six distinct tetrahedral orientations of the hyperfine tensor at the labeled segment are required for a consistent description of the chain isomerism. For the C-6 segment only the 0 degree (trans) and two 60 degrees (gauche) orientations are significantly populated, for the C-10 position two further 60 degrees orientations are populated, and for the C-13 position all orientations have non-vanishing populations. Detailed comparisons have been made with the results of 2H nuclear magnetic resonance (NMR) measurements on dimyristoylphosphatidylcholine labeled at the same position in the sn-2 chain, and using an identical motional model. The parameters of overall reorientation, both order parameter and correlation times, have very similar values as determined by ESR and NMR.

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Language(s): eng - English
 Dates: 1989-01
 Publication Status: Published in print
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 Rev. Method: Peer
 Identifiers: DOI: 10.1016/S0006-3495(89)82784-5
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Title: Biophysical Journal
Source Genre: Journal
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Pages: - Volume / Issue: 55 (1) Sequence Number: - Start / End Page: 111 - 123 Identifier: -