Evolution of CPMAS under fast magic-angle-spinning at 100 kHz and beyond

This article describes recent trends of high-field solid-state NMR (SSNMR) experiments for small organic molecules and biomolecules using C-13 and N-15 CPMAS under ultra-fast MAS at a spinning speed (nu(R)) of 80-100 kHz. First, we illustrate major differences between a modern low-power RF scheme using UFMAS in an ultra-high field and a traditional CPMAS scheme using a moderate sample spinning in a lower field. Features and sensitivity advantage of a low-power RF scheme using UFMAS and a small sample coil are summarized for CPMAS-based experiments. Our 1D C-13 CPMAS experiments for uniformly C-13- and 15N-labeled alanine demonstrated that the sensitivity per given sample amount obtained at viz of 100 kHz and a H-1 NMR frequency (vH) of 750.1 MHz is similar to 10 fold higher than that of a traditional CPMAS experiment obtained at nu(R) of 20 kHz and nu(H) of 400.2 MHz. A comparison of different 1H-decoupling schemes in CPMAS at nu(R) of 100 kHz for the same sample demonstrated that low-power WALTZ-16 decoupling unexpectedly displayed superior performance over traditional low-power schemes designed for SSNMR such as TPPM and XiX in a range of decoupling field strengths of 5-20 kHz. Excellent 1H decoupling performance of WALTZ-16 was confirmed on a protein microcrystal sample of GB1 at viz of 80 kHz. We also discuss the feasibility of a SSNMR microanalysis of a GB1 protein sample in a scale of 1 nmol to 80 nmol by H-1-detected 2D N-15/H-1 SSNMR by a synergetic use of a high field, a low-power RF scheme, a paramagnetic-assisted condensed data collection (PACC), and UFMAS. (C) 2015 Elsevier Inc. All rights reserved.