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Model-free estimation of the effective correlation time for C-H bond reorientation in amphiphilic bilayers: (1)H-(13)C solid-state NMR and MD simulations.

Ferreira, Tiago LU ; Ollila, Samuli LU ; Pigliapochi, Roberta LU ; Dabkowska, Aleksandra LU and Topgaard, Daniel LU (2015) In Journal of Chemical Physics 142(4).
Abstract
Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of (13)C or (2)H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation... (More)
Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of (13)C or (2)H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time τe, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of (13)C R1 and R1ρ relaxation rates, as well as (1)H-(13)C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τe from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τe-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τe-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Journal of Chemical Physics
volume
142
issue
4
publisher
American Institute of Physics
external identifiers
  • pmid:25638007
  • wos:000349018100048
  • scopus:84923783829
ISSN
0021-9606
DOI
10.1063/1.4906274
language
English
LU publication?
yes
id
3f35e9a3-d66e-43f7-bbbe-46c72d561247 (old id 5145761)
date added to LUP
2015-03-09 17:07:11
date last changed
2017-10-22 03:13:58
@article{3f35e9a3-d66e-43f7-bbbe-46c72d561247,
  abstract     = {Molecular dynamics (MD) simulations give atomically detailed information on structure and dynamics in amphiphilic bilayer systems on timescales up to about 1 μs. The reorientational dynamics of the C-H bonds is conventionally verified by measurements of (13)C or (2)H nuclear magnetic resonance (NMR) longitudinal relaxation rates R1, which are more sensitive to motional processes with correlation times close to the inverse Larmor frequency, typically around 1-10 ns on standard NMR instrumentation, and are thus less sensitive to the 10-1000 ns timescale motion that can be observed in the MD simulations. We propose an experimental procedure for atomically resolved model-free estimation of the C-H bond effective reorientational correlation time τe, which includes contributions from the entire range of all-atom MD timescales and that can be calculated directly from the MD trajectories. The approach is based on measurements of (13)C R1 and R1ρ relaxation rates, as well as (1)H-(13)C dipolar couplings, and is applicable to anisotropic liquid crystalline lipid or surfactant systems using a conventional solid-state NMR spectrometer and samples with natural isotopic composition. The procedure is demonstrated on a fully hydrated lamellar phase of 1-palmitoyl-2-oleoyl-phosphatidylcholine, yielding values of τe from 0.1 ns for the methyl groups in the choline moiety and at the end of the acyl chains to 3 ns for the g1 methylene group of the glycerol backbone. MD simulations performed with a widely used united-atom force-field reproduce the τe-profile of the major part of the acyl chains but underestimate the dynamics of the glycerol backbone and adjacent molecular segments. The measurement of experimental τe-profiles can be used to study subtle effects on C-H bond reorientational motions in anisotropic liquid crystals, as well as to validate the C-H bond reorientation dynamics predicted in MD simulations of amphiphilic bilayers such as lipid membranes.},
  articleno    = {044905},
  author       = {Ferreira, Tiago and Ollila, Samuli and Pigliapochi, Roberta and Dabkowska, Aleksandra and Topgaard, Daniel},
  issn         = {0021-9606},
  language     = {eng},
  number       = {4},
  publisher    = {American Institute of Physics},
  series       = {Journal of Chemical Physics},
  title        = {Model-free estimation of the effective correlation time for C-H bond reorientation in amphiphilic bilayers: (1)H-(13)C solid-state NMR and MD simulations.},
  url          = {http://dx.doi.org/10.1063/1.4906274},
  volume       = {142},
  year         = {2015},
}