Centerband-only-detection-of-exchange ³¹P nuclear magnetic resonance and phospholipid lateral diffusion: theory, simulation and experiment

Abstract

Centerband-only-detection-of-exchange (CODEX) (31)P NMR lateral diffusion measurements were performed on dimyristoylphosphatidylcholine (DMPC) assembled into large unilamellar spherical vesicles. Optimization of sample and NMR acquisition conditions provided significant sensitivity enhancements relative to an earlier first report (Q. Saleem, A. Lai, H. Morales, and P. M. Macdonald, Chem. Phys. Lipids, 2012, 165, 721). An analytical description was developed that permitted the extraction of lateral diffusion coefficients from CODEX data, based on a Gaussian-diffusion-on-a-sphere model (A. Ghosh, J. Samuel, and S. Sinha, Europhys. Lett., 2012, 98, 30003-p1) as relevant to CODEX (31)P NMR measurements on a population of spherical unilamellar phospholipid bilayer vesicles displaying a distribution of vesicle radii.

Solid-State NMR Dipolar and Chemical Shift Anisotropy Recoupling Techniques for Structural and Dynamical Studies in Biological Systems

“…Similar to dipolar coupling, CSA provides another powerful tool for probing the motional behaviors in biosystems, for example, the dynamics of the backbone 36,407,420,421,445−447 and side chains 386,448,449 of peptides/proteins, as well as the diffusion of biomolecules such as proteins 388 and phospholipids. 389 In general, the size of the CSA for spin-1/2 nuclei covers a very wide range, from <5 ppm for aliphatic protons to >200 ppm for 19 F, 31 P, and 13 C, in accordance with a broad range of motional time scales. In this section, the discussion of CSA recoupling in dynamic studies is categorized into fast-, intermediate-, and slow-motion regimes, as that for the application of dipolar coupling in section 4.3.2.…”

“…For example, the CSA tensors of 1 H, 13 C, and 15 N in a hydrogen-bonding environment are notably different compared to those without hydrogen bondings, with particular principal components even being linearly responsive to the hydrogen-bonding strength. ,, Specifically for protons, its small CSA and narrow chemical shift range render the detection of proton CSA particularly challenging, but the high sensitivity and natural abundance make the investigation of proton CSA an attracting project. For 13 C CSA, in addition to hydrogen bonding, both the orientations and magnitudes of the principal components of 13 C α CSA in proteins are noticeably different between helical and sheet domains, providing important constraints for accurate structure determinations. ,, As the CSA and dipolar coupling tensors can be encoded together as a function of the molecular orientation, the combined analyses of CSA and heteronuclear dipolar recoupling interactions provides additional information for refining or determining high-resolution structures. ,, Besides, similar to dipolar coupling, CSA can also be used to reveal the dynamical information in fast, intermediate, and slow motions. − …”

“…Similar to dipolar coupling, CSA provides another powerful tool for probing the motional behaviors in biosystems, for example, the dynamics of the backbone ,,,,− and side chains ,, of peptides/proteins, as well as the diffusion of biomolecules such as proteins and phospholipids . In general, the size of the CSA for spin-1/2 nuclei covers a very wide range, from <5 ppm for aliphatic protons to >200 ppm for 19 F, 31 P, and 13 C, in accordance with a broad range of motional time scales.…”

“…In membrane systems, the dynamics of the phospholipid, e.g., lateral diffusion, also plays a crucial part in the membrane function. Based on 31 P CODEX, Lai et al developed the theory and method for characterizing the lateral diffusion of phospholipids in a membrane . The 31 P CODEX decay curves were analyzed via powder averaging results based on the Gaussian-diffusion-on-a-sphere model, and the lateral diffusion coefficients of DMPC in DMPC/AECHO large unilamellar vesicles were obtained …”

“…Based on 31 P CODEX, Lai et al developed the theory and method for characterizing the lateral diffusion of phospholipids in a membrane. 389 The 31 P CODEX decay curves were analyzed via powder averaging results based on the Gaussian-diffusion-on-a-sphere model, and the lateral diffusion coefficients of DMPC in DMPC/AECHO large unilamellar vesicles were obtained. 389 Note the above discussion about CSA is mainly focused on the nuclei with large anisotropy, owing to their relatively high electron density and relatively small or negligible homonuclear dipolar coupling.…”