Systems and Structural Biology Center, RIKEN, Yokohama 230-0045, Japan.
J Magn Reson. 2010 Apr;203(2):274-82. doi: 10.1016/j.jmr.2010.01.007. Epub 2010 Jan 18.
We have begun a project to develop an NMR spectrometer that operates at frequencies beyond 1 GHz (magnetic field strength in excess of 23.5 T) using a high temperature superconductor (HTS) innermost coil. As the first step, we developed a 500 MHz NMR with a Bi-2223 HTS innermost coil, which was operated in external current mode. The temporal magnetic field change of the NMR magnet after the coil charge was dominated by (i) the field fluctuation due to a DC power supply and (ii) relaxation in the screening current in the HTS tape conductor; effect (i) was stabilized by the 2H field-frequency lock system, while effect (ii) decreased with time due to relaxation of the screening current induced in the HTS coil and reached 10(-8)(0.01 ppm)/h on the 20th day after the coil charge, which was as small as the persistent current mode of the NMR magnet. The 1D (1)H NMR spectra obtained by the 500 MHz LTS/HTS magnet were nearly equivalent to those obtained by the LTS NMR magnet. The 2D-NOESY, 3D-HNCO and 3D-HNCACB spectra were achieved for ubiquitin by the 500 MHz LTS/HTS magnet; their quality was closely equivalent to that achieved by a conventional LTS NMR. Based on the results of numerical simulation, the effects of screening current-induced magnetic field changes are predicted to be harmless for the 1.03 GHz NMR magnet system.
我们已经开始了一个项目，旨在开发一种使用高温超导体（HTS）内圈的工作频率超过 1GHz（磁场强度超过 23.5T）的 NMR 光谱仪。作为第一步，我们开发了一种使用 Bi-2223 HTS 内圈的 500MHz NMR，它采用外部电流模式运行。在对线圈充电后，NMR 磁铁的磁场随时间的变化主要由以下两个因素决定：（i）直流电源引起的磁场波动，以及（ii）HTS 带材导体中的屏蔽电流弛豫；效应（i）通过 2H 场频锁定系统得到稳定，而效应（ii）由于 HTS 线圈中感应的屏蔽电流弛豫而随时间减小，在对线圈充电后的第 20 天达到 10(-8)(0.01ppm)/h，这与 NMR 磁铁的持续电流模式一样小。由 500MHz LTS/HTS 磁铁获得的 1D(1)H NMR 谱与由 LTS NMR 磁铁获得的谱几乎相同。通过 500MHz LTS/HTS 磁铁实现了对泛素的 2D-NOESY、3D-HNCO 和 3D-HNCACB 谱；其质量与传统 LTS NMR 相当。基于数值模拟的结果，预测屏蔽电流引起的磁场变化的影响对 1.03GHz NMR 磁铁系统是无害的。
