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

Abstract

We describe a simple yet highly effective optimization strategy for SPINAL-64 1H 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 13C and 15N show significant enhancement (up to 64%), relative to the previous described SPINAL-64 conditions, under the moderate 1H 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 1H decoupling schemes (TPPM, XiX), as well as SPINAL-64 with the originally reported optimal values.