Refocused CSA rotating frame relaxation experiment with a double cross polarization module, measuring 13C T1rho

This is NYSBC standard data set and pulse program for 1H-15N-13C double cross polarization followed by 13C RECRR spinlock and 13C acquisition with 1H decoupling. The pulse program has power safety limitations specific for the particular probe. The pulse program dbcp_13CRECRR_3.2EF750.nysbc, ramp shape file tancn_100_SCALE and include file power_intro.incl are located in the dataset directory.

This experiment measures rotating frame relaxation rate. It refocuses CSA and it is less sensitive to carrier frequency offset, coil based rf-inhomogeneity and imprefections in RF pulses.

Citation

https://www.sciencedirect.com/science/article/abs/pii/S1090780718302295 Refocusing CSA during magic angle spinning rotating frame relaxation experiments, Eric Keeler, Keith Fritzsching, Ann E McDermott Joural of Magnetic Resonance, 2018 296, 130-137

https://www.tandfonline.com/doi/abs/10.1080/00268979809483251 Cross polarization in the tilted frame: assignment and spectral simplification in heteronuclear spin systems, Marc Baldus, Aneta Petkova, Judith Herzfeld and Robert G. Griffin, Journal of Molecular Physics, 1998, 95(6),1197-1207

Sample heating

To minimized heating of conductive samples, we recommend using an Efree/lowE probe. However, a combination of frictional heating from spinning and RF heating on long pulses on both channel may cause substantial sample heating and temperature gradient across the sample even in an Efree probe. The heating may damage the sample. The heating and temperature gradient across the rotor may substantially compromise the precision of measurements and data fitting. The combination of long DCP and spin locking pulses causes substantial short term and long term heating (it builds up over several hours). To maintain the heating constant, the experiment has a compensation pulse.

Citation

https://www.ncbi.nlm.nih.gov/pubmed/10868566?dopt=Abstract Heating of samples induced by fast magic-angle spinning, Brus, J., Solid State Nucl. Magn. Reson. 16, 151–160 (2000).

https://onlinelibrary.wiley.com/doi/abs/10.1002/mrc.4450 Heating and temperature gradients of lipid bilayer samples induced by RF irradiation in MAS solid-state NMR experiments, Wang, J., Zhang, Z., Zhao, W., Wang, L. & Yang, J., Magn. Reson. Chem. 54, 753–759 (2016).

https://www.biorxiv.org/content/10.1101/566729v1.full TmDOTP : An NMR- based Thermometer for Magic Angle Spinning NMR Experiments Dongyu Zhang, Boris Itin, Ann E. McDermott; preprinted

Probe and power limitations

R1ρ experiments require long simultaneous medium to high power pulses on all channels. Adjust the probe power and length limitations in the pulse sequence to follow your probe's specifications. When in doubt, contact the manufacturer.

Protocol

Carefully optimize CP and DCP conditions. Make sure that RECRR pulses are rotor synchronized. Set up a series of 2D experiments varying power and length of the spin locking pulse.

Samples

The experiments were performed with crystallized u-15N,13C-labeled-N-acetyl-valine and u-15N,13C membrane protein in hydrated lipids.

Processing and analysis

Use a processing software of your choice (Topspin, NMRpipe, etc...) to Fourier transform 2D experiments and pick peaks. If using automatic peak picking routines, verify the peaks manually. Measure the peak intensities as a function of length of the spin locking pulse and use a monoexponential function to obtain R1ρ values. You can use INFOS software in MATLAB for quicker peak picking and data fitting.

Citation

https://www.ncbi.nlm.nih.gov/pubmed/28160196 INFOS: spectrum fitting software for NMR analysis, Smith AA, Journal of Biomolecular NMR, 2017, 67(2), 77-94

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Pulse Sequence and Parameter Set