Open AccessImproving the quality of oriented membrane protein spectra using heat-compensated separated local field experiments
Author(s) -
Songlin Wang,
T. Gopinath,
Gianluigi Veglia
Publication year - 2019
Publication title -
journal of biomolecular nmr
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.346
H-Index - 106
eISSN - 1573-5001
pISSN - 0925-2738
DOI - 10.1007/s10858-019-00273-1
Subject(s) - chemistry , model lipid bilayer , pulse sequence , relaxation (psychology) , anisotropy , paramagnetism , dipole , nuclear magnetic resonance , spectral line , membrane , spectroscopy , analytical chemistry (journal) , pulse (music) , lipid bilayer , molecular physics , condensed matter physics , physics , optics , chromatography , lipid bilayer phase behavior , psychology , social psychology , biochemistry , organic chemistry , quantum mechanics , astronomy , detector
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.