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Can PISEMA experiments be used to extract structural parameters for mobile beta-barrels?
Dustin W Bleile1, Walter R P Scott, Suzana K Straus
1Department of Chemistry, University of British Columbia, 2036 Main Mall, Vancouver, B.C., V6T 1Z1, Canada.
Journal of Biomolecular NMR
|July 22, 2005
Summary
Molecular dynamics simulations reveal that peptide plane mobility significantly impacts solid-state NMR PISEMA spectra of beta-barrels. Specific chemical shift anisotropy parameters, particularly theta, and NH bond distance are crucial for accurate spectral interpretation and peak assignment.
Area of Science:
- Biophysics
- Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
- Computational Chemistry
Background:
- Macroscopically oriented beta-barrels are crucial membrane proteins.
- Solid-state NMR, specifically 15N chemical shift/15N-(1)H dipolar coupling (PISEMA), is a powerful tool for structural analysis.
- Understanding the influence of molecular dynamics on NMR spectra is essential for accurate structural determination.
Purpose of the Study:
- To investigate the effect of molecular mobility on PISEMA solid-state NMR experiments for oriented beta-barrels.
- To evaluate the impact of chemical shift anisotropy (CSA) and dipolar coupling parameters on PISEMA spectra of beta-barrels.
- To explore the utility of PISEMA spectral patterns for peak assignment in beta-barrel structures.
Main Methods:
- Utilized molecular dynamics (MD) simulation data of the NalP autotransporter domain within a DMPC bilayer.
- Calculated PISEMA spectra based on MD simulation data.
- Assessed the influence of peptide plane librational motion on spectral features.
- Evaluated the dependence of CSA parameters (sigma11, sigma22, sigma33, theta) and NH bond distance on spectral outcomes.
Main Results:
- Fast librational motion of peptide planes significantly affects calculated PISEMA spectra, consistent with findings for alpha-helices.
- The CSA parameter theta has a substantial impact on peak positions (up to 20 ppm shift) and spectral shape, while other CSA parameters have minor effects.
- The NH bond distance strongly influences the dipolar coupling constant used in calculations.
- Distinct spectral patterns emerge for alternating beta-strands, suggesting potential for peak assignment.
Conclusions:
- Molecular mobility is a critical factor influencing PISEMA spectra of oriented beta-barrels.
- Precise selection of CSA parameters, especially theta, and NH bond distance is vital for accurate spectral simulation and interpretation.
- The observed spectral patterns offer a promising avenue for assigning peaks in complex beta-barrel structures using solid-state NMR.