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 13 C and 15 N CPMAS under ultra-fast MAS at a spinning speed ( ν 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 13 C CPMAS experiments for uniformly 13 C- and 15 N-labeled alanine demonstrated that the sensitivity per given sample amount obtained at ν R of 100 kHz and a 1 H NMR frequency ( ν H ) of 750.1 MHz is ~10 fold higher than that of a traditional CPMAS experiment obtained at ν R of 20 kHz and ν H of 400.2 MHz. A comparison of different 1 H-decoupling schemes in CPMAS at ν 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 1 H decoupling performance of WALTZ-16 was confirmed on a protein microcrystal sample of GB1 at ν R 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 1 H-detected 2D 15 N/ 1 H SSNMR by a synergetic use of a high field, a low-power RF scheme, a paramagnetic-assisted condensed data collection (PACC), and UFMAS. [ABSTRACT FROM AUTHOR]