title: Closed-cycle cold helium magic-angle spinning for sensitivity-enhanced multi-dimensional solid-state NMR.
abstract: Magic-angle spinning (MAS) NMR is a powerful tool for studying molecular structure and dynamics, but suffers from its low sensitivity. Here, we developed a novel helium-cooling MAS NMR probe system adopting a closed-loop gas recirculation mechanism. In addition to the sensitivity gain due to low temperature, the present system has enabled highly stable MAS (vR=4-12 kHz) at cryogenic temperatures (T=35-120 K) for over a week without consuming helium at a cost for electricity of 16 kW/h. High-resolution 1D and 2D data were recorded for a crystalline tri-peptide sample at T=40 K and B0=16.4 T, where an order of magnitude of sensitivity gain was demonstrated versus room temperature measurement. The low-cost and long-term stable MAS strongly promotes broader application of the brute-force sensitivity-enhanced multi-dimensional MAS NMR, as well as dynamic nuclear polarization (DNP)-enhanced NMR in a temperature range lower than 100 K.
authors: Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan.
authors: Yoh
authors: Y
authors: Matsuki
authors: JEOL RESONANCE Inc., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
authors: Shinji
authors: S
authors: Nakamura
authors: Cryovac Corporation, 2-12-14 Chibune, Nishi Yodogawa, Osaka 555-0013, Japan.
authors: Shigeo
authors: S
authors: Fukui
authors: JEOL RESONANCE Inc., 3-1-2 Musashino, Akishima, Tokyo 196-8558, Japan.
authors: Hiroto
authors: H
authors: Suematsu
authors: Institute for Protein Research, Osaka University, 3-2 Yamadaoka, Suita, Osaka 565-0871, Japan. Electronic address: tfjwr@protein.osaka-u.ac.jp.
authors: Toshimichi
authors: T
authors: Fujiwara
mesh_terms: D003080:Cold Temperature; D004560:Electricity; D006371:Helium / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000191:economics / Q000295:instrumentation / Q000379:methods*; D013696:Temperature
chemical_list: D006371:Helium
keywords: Closed-loop helium circulation; Cryogenic magic-angle spinning; Sensitivity enhancement; Solid-state NMR