[NMR paper] Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.
Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.
Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.
J Magn Reson. 2015 Apr 28;256:14-22
Authors: Koroloff SN, Nevzorov AA
Abstract
Solid-state NMR (ssNMR) of oriented membrane proteins (MPs) is capable of providing structural and dynamic information at nearly physiological conditions. However, NMR experiments performed on oriented membrane proteins generally suffer from low sensitivity. Moreover, utilization of high-power radiofrequency (RF) irradiations for magnetization transfer may give rise to sample heating, thereby decreasing the efficiency of conventional cross-polarization schemes. Here we have optimized the recently developed repetitive cross-polarization (REP-CP) sequence (Tang et al., 2011) to further increase the magnetization transfer efficiency for membrane proteins reconstituted in magnetically aligned bicelles and compared its performance to single-contact Hartmann-Hahn cross-polarization (CP), CP-MOIST and the adiabatic transfer. It has been found that employing the REP-CP sequence at RF amplitudes of 19kHz instead of the commonly used higher RF fields (>45kHz) enhances the efficiency of REP-CP. An additional 30% signal can be obtained as compared to the previously published REP-CP, and 20% when compared to the re-optimized REP-CP at 50kHz RF fields. Moreover, the (15)N signal gain of low-power REP-CP was found to be 40% over the adiabatic CP and up to 80% over CP-MOIST. Thus, the low-power REP-CP sequence surpasses all of the previous CP schemes in addition of having the tremendous advantage of reducing the RF powers by a factor of seven, thereby preserving the liquid-like bicelle sample. By contrast, in purely static (NAL crystal) and semi-rigid systems (Pf1 phage), the adiabatic CP was found to be more effective. Periodic oscillations of the intensity profile (distinct from the transient oscillations) as a function of the CP contact time and B1 RF field strengths were observed during the REP-CP optimization with the oscillations becoming more pronounced with lower RF fields. Many-spin simulations were performed to explain the oscillations and their periodicity.
PMID: 25965279 [PubMed - as supplied by publisher]
[NMR paper] Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles
Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles
Publication date: Available online 28 April 2015
Source:Journal of Magnetic Resonance</br>
Author(s): Sophie N. Koroloff , Alexander A. Nevzorov</br>
Solid-state NMR (ssNMR) of oriented membrane proteins (MPs) is capable of providing structural and dynamic information at nearly physiological conditions. However, NMR experiments performed on oriented membrane proteins generally suffer from...
[NMR paper] Sensitivity enhancement and contrasting information provided by free radicals in oriented-sample NMR of bicelle-reconstituted membrane proteins.
Sensitivity enhancement and contrasting information provided by free radicals in oriented-sample NMR of bicelle-reconstituted membrane proteins.
Related Articles Sensitivity enhancement and contrasting information provided by free radicals in oriented-sample NMR of bicelle-reconstituted membrane proteins.
J Magn Reson. 2013 Nov 28;239C:9-15
Authors: Tesch DM, Nevzorov AA
Abstract
Elucidating structure and topology of membrane proteins (MPs) is essential for unveiling functionality of these important biological constituents. Oriented-sample...
nmrlearner
Journal club
0
12-21-2013 03:15 PM
A spectroscopic assignment technique for membrane proteins reconstituted in magnetically aligned bicelles
A spectroscopic assignment technique for membrane proteins reconstituted in magnetically aligned bicelles
Abstract Oriented-sample NMR (OS-NMR) has emerged as a powerful tool for the structure determination of membrane proteins in their physiological environments. However, the traditional spectroscopic assignment method in OS NMR that uses the â??shotgunâ?? approach, though effective, is quite labor- and time-consuming as it is based on the preparation of multiple selectively labeled samples. Here we demonstrate that, by using a combination of the spin exchange under mismatched...
nmrlearner
Journal club
0
09-17-2012 02:05 AM
Multidimensional oriented solid-state NMR experiments enable the sequential assignment of uniformly 15N labeled integral membrane proteins in magnetically aligned lipid bilayers
Multidimensional oriented solid-state NMR experiments enable the sequential assignment of uniformly 15N labeled integral membrane proteins in magnetically aligned lipid bilayers
Abstract Oriented solid-state NMR is the most direct methodology to obtain the orientation of membrane proteins with respect to the lipid bilayer. The method consists of measuring 1H-15N dipolar couplings (DC) and 15N anisotropic chemical shifts (CSA) for membrane proteins that are uniformly aligned with respect to the membrane bilayer. A significant advantage of this approach is that tilt and azimuthal...
Repetitive cross-polarization contacts via equilibration-re-equilibration of the proton bath: sensitivity enhancement for NMR of membrane proteins reconstituted in magnetically aligned bicelles
Repetitive cross-polarization contacts via equilibration-re-equilibration of the proton bath: sensitivity enhancement for NMR of membrane proteins reconstituted in magnetically aligned bicelles
Publication year: 2011
Source: Journal of Magnetic Resonance, In Press, Accepted Manuscript, Available online 2 July 2011</br>
Wenxing, Tang , Alexander A., Nevzorov</br>
Thermodynamic limit of magnetization corresponding to the intact proton bath often cannot be transferred in a single cross-polarization contact. This is mainly due to the finite ratio between the number densities of the high-...
Optimization of cross-polarization at low radiofrequency fields for sensitivity enhancement in solid-state NMR of membrane proteins reconstituted in magnetically aligned bicelles.
Linear Mode
