Solid-state 2 H NMR studies of water- mediated lipid membrane deformation

Trivikram R. Molugu, Xiaolin Xu, Soohyun Lee, K. J. Mallikarjunaiah, Michael F. Brown

Research output: Chapter in Book/Report/Conference proceedingChapter

1 Scopus citations

Abstract

The application of solid-state 2 H nuclear magnetic resonance (NMR) spectroscopy gives a powerful approach for investigating hydration-mediated effects on lipid bilayer structure and dynamics. The extent to which lipid bilayers are deformed by dehydration stress is inherent to understanding how lipid-protein interactions affect biomembrane functioning. For liquid-crystalline membranes, the average structure is manifested by the segmental order parameters (S CD ) of the lipids. Structural quantities, such as the area per lipid and volumetric bilayer thickness, are obtained by a mean-torque analysis of 2 H NMR order parameters. Removal of water in the liquid-crystalline state gives a reduction of the mean area per lipid, together with a corresponding increase in volumetric bilayer thickness. Measurements of order parameters versus osmotic pressure yield the elastic area compressibility modulus and the corresponding bilayer thickness at an atomistic level. Furthermore, solid-state 2 H NMR relaxation rates of lipid bilayers at varying hydration levels afford new insights into the role of water in membrane structural dynamics and viscoelastic properties. Model-free interpretation of spinlattice (R 1Z ) and transverse (R QE 2 ) relaxation rates suggests that collective chain motions described as order-director fluctuations dominantly contribute to the relaxation. In a continuum picture, elastic deformations in such materials are collective hydrodynamic phenomena with motional time scales spanning many decades (picoseconds to seconds). The dynamic processes mainly affecting the spin-spin relaxation have characteristic time scales much longer than those contributing to spin-lattice relaxation. Such studies probe membrane interactions involving collective bilayer undulations, order-director fluctuations, and lipid molecular protrusions, giving a unique source of information about intermolecular forces pertinent to biomembrane structure and function.

Original languageEnglish (US)
Title of host publicationModern Magnetic Resonance
PublisherSpringer International Publishing
Pages1225-1250
Number of pages26
ISBN (Electronic)9783319283883
ISBN (Print)9783319283876
DOIs
StatePublished - Jun 13 2018

Keywords

  • Lipid bilayers
  • Liquid crystals
  • Membrane elasticity
  • Membranes deformation
  • Molecular dynamics
  • NMR relaxation
  • NMR spectroscopy
  • Order-director fluctuations
  • Osmotic stress

ASJC Scopus subject areas

  • Engineering(all)
  • Materials Science(all)
  • Medicine(all)
  • Social Sciences(all)
  • Arts and Humanities(all)
  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)

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