Meirovitch E, Liang Z, Freed JH. Protein Dynamics in the Solid State from (2)H NMR Line Shape Analysis. II. MOMD Applied to C-D and C-CD3 Probes.
J Phys Chem B 2015;
119:14022-32. [PMID:
26402431 PMCID:
PMC4676681 DOI:
10.1021/acs.jpcb.5b07434]
[Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
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Deuterium
line shape analysis from mobile C–D and C–CD3 groups has emerged as a particularly useful tool for studying
dynamics in the solid state. The theoretical models devised so far
consist typically of sets of independent dynamic modes. Each such
mode is simple and usually case-specific. In this scenario, model
improvement entails adding yet another mode (thereby changing the
overall model), comparison of different cases is difficult, and ambiguity
is unavoidable. We recently developed the microscopic order macroscopic
disorder (MOMD) approach as a single-mode alternative. In MOMD, the
local spatial restrictions are expressed by an anisotropic potential,
the local motion by a diffusion tensor, and the local molecular geometry
by relative (magnetic and model-related) tensor orientations, all
of adjustable symmetry. This approach provides a consistent method
of analysis, thus resolving the issues above. In this study, we apply
MOMD to PS-adsorbed LKα14 peptide and dimethylammonium tetraphenylborate
(C–CD3 and N–CD3 dynamics, respectively),
as well as HhaI methyltransferase target DNA and
phase III of benzene-6-hexanoate (C–D dynamics). The success
with fitting these four disparate cases, as well as the two cases
in the previous report, demonstrates the generality of this MOMD-based
approach. In this study, C–D and C–CD3 are
both found to execute axial diffusion (rates R⊥ and R∥) in the
presence of a rhombic potential given by the L =
2 spherical harmonics (coefficients c02 and c22). R⊥ (R∥) is in the 102–103 (104–105) s–1 range, and c02 and c22 are on the
order of 2–3 kBT. Specific parameter values are determined for each mobile site.
The diffusion and quadrupolar tensors are tilted at either 120°
(consistent with trans–gauche isomerization) or nearly 110.5° (consistent with methyl exchange).
Future prospects include extension of the MOMD formalism to include
MAS, and application to 15N and 13C nuclei.
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