Straightforward, effective calibration of SPINAL-64 decoupling results in the enhancement of sensitivity and resolution of biomolecular solid-state NMR

We describe a simple yet highly effective optimization strategy for SPINAL-64 H-1 decoupling conditions for magic-angle spinning solid-state NMR. With adjustment of the phase angles in a coupled manner, the optimal conditions resulting from three parameter optimizations can be determined with adjustment of a single phase. Notably, echo T-2 relaxation times for C-13 and N-15 show significant enhancement (up to 64%), relative to the previous described SPINAL-64 conditions, under the moderate H-1 decoupling levels (60-100 kHz) and MAS rate (13.3 kHz) commonly employed for high-resolution SSNMR spectroscopy of proteins. Additionally, we also investigated the effect at higher spinning rate (33.3 kHz) and compared the results with other H-1 decoupling schemes (TPPM, XiX), as well as SPINAL-64 with the originally reported optimal values. Published by Elsevier Inc.