Improving the quality of oriented membrane protein spectra using heat-compensated separated local field experiments

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3 Scopus citations

Abstract

Oriented sample solid-state NMR (OS-ssNMR) spectroscopy is a powerful technique to determine the topology of membrane proteins in oriented lipid bilayers. Separated local field (SLF) experiments are central to this technique as they provide first-order orientational restraints, i.e., dipolar couplings and anisotropic chemical shifts. Despite the use of low-E (or E-free) probes, the heat generated during the execution of 2D and 3D SLF pulse sequences causes sizeable line-shape distortions. Here, we propose a new heat-compensated SE-SAMPI4 (hcSE-SAMPI4) pulse sequence that holds the temperature constant for the duration of the experiment. This modification of the SE-SAMPI4 results in sharper and more intense resonances without line-shape distortions. The spectral improvements are even more apparent when paramagnetic relaxation agents are used to speed up data collection. We tested the hcSE-SAMPI4 pulse sequence on a single-span membrane protein, sarcolipin (SLN), reconstituted in magnetically aligned lipid bicelles. In addition to eliminating peak distortions, the hcSE-SAMPI4 experiment increased the average signal-to-noise ratio by 20% with respect to the original SE-SAMPI4.

Original languageEnglish (US)
Pages (from-to)617-624
Number of pages8
JournalJournal of biomolecular NMR
Volume73
Issue number10-11
DOIs
StatePublished - Nov 1 2019

Bibliographical note

Funding Information:
This research is supported by the National Institute of Health (GM 64742 and HL 144130 to G.V.). The authors would like to acknowledge Dr. Peter Gor’kov from the National High Magnetic Fields Laboratory in Florida, Prof. Alex Nevzorov from NCSU, and Dr. Daniel Weber for helpful discussions.

Funding Information:
This research is supported by the National Institute of Health (GM 64742 and HL 144130 to G.V.). The authors would like to acknowledge Dr. Peter Gor?kov from the National High Magnetic Fields Laboratory in Florida, Prof. Alex Nevzorov from NCSU, and Dr. Daniel Weber for helpful discussions.

Keywords

  • Bicelles
  • Heat compensation
  • Membrane proteins
  • Oriented-sample solid-state NMR
  • Paramagnetic relaxation enhancement
  • SAMPI4
  • Sarcolipin

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