BioSpin Sets Record with 1.1 GHz NMR Magnet

Bruker BioSpin has developed an ultra-high field superconducting 1.1 GHz spectrometer for increased sensitivity and higher resolution NMR in structural biology. The Ascend 1.1 GHz NMR magnet was successfully energized in late 2018 and has since undergone a series of successful experiments at Bruker’s Swiss GHz-class magnet factory.  Expectations are that it will be installed in the Structural Biology Department at St. Jude’s Children Research Hospital in Memphis, Tennessee, once all factory tests have been completed.

“This is the first stable, homogeneous magnet for high-resolution NMR in structural biology,” Bruker commented by email. “High-resolution NMR magnets are special in the sense that the field they generate is extremely stable over time and extremely homogenous in space. No other magnet suitable for high resolution NMR has ever reached a field of 1.1 GHz; this is the world record.

“To put this in perspective: the stability of the 1.1 GHz is so good that the full field of Hz decays by less than 40 Hz per hour. This can then be brought to virtually zero by the Bruker digital lock system.

“In addition, for solid state NMR experiments without the possibility to lock, the rate with which the field decays must be extremely stable; i.e., the field decay must be almost perfectly linear over time. The base homogeneity of the 1.1 GHz is so good that we can use our room temperature shim systems (field shaping coils) such that the field in the active sample volume does not vary by more than a fraction of 1 Hz.”

Magnet to Provide Access to Previously Inaccessible Data

The magnet addresses the scientific requirements for virtually all existing applications carried out with NMR at lower fields. Its increased field has special benefits for materials science applications, such as the solid state NMR of quadrupolar nuclei, and structural biology applications, such as intrinsically disordered proteins (IDP) analysis. All field dependent effects, such as paramagnetic sample alignment, chemical exchange regime, and relaxation effects, can now be studied at this higher field, thus enabling access to previously inaccessible experimental data.

For many years, high-resolution NMR was limited to a magnetic field of 23.5 T, equivalent to a 1H resonance frequency of 1.0 GHz. This limit was set by the physical properties of low temperature superconductors, and was first reached in 2009 by BioSpin with an Avance 1000 spectrometer at the Ultra-High Field NMR Center in Lyon, France. High temperature superconductors offered even higher magnetic fields at low temperatures, but considerable challenges in YBCO HTS tape manufacturing and in superconducting magnet technology slowed efforts to take advantage of the technology for further progress.

Spectrometer Combines HTS and LTS Technology

The new BioSpin magnet employs a hybrid technology that combines both LTS and HTS wires. The HTS segment represents the internal section and is jointed to the LTS coil. REBCO is used as the high temperature superconductor and NbTi and Nb3Ti for the low temperature superconductors.

BioSpin successfully developed solutions to overcome the technical challenges inherent in creating this type of magnet. These included handling the hoop stress and axial pressure that occur at such high current densities, coping with screening current effects, quench protection of the HTS magnets, and the low drift rates compatible with high-resolution NMR.

“Our 1.1 GHz is a ‘customer product’ in the sense that the operator does not need to be a superconductivity or cryogenics expert to run the system, that the siting is straightforward,” Bruker said by email. “In addition, the helium consumption had to be reasonable, to keep the operating cost low. The requirement for low helium consumption precludes the use of an external magnet current supply, since the heat load would be enormous if the magnet current had to be passed to the liquid helium stage of the cryostat.”

Stronger 1.2 GHz Magnet in Development

BioSpin’s 1.1 GHz magnet is considered to be an important stepping stone towards a 1.2 GHz NMR spectrometer that the company is currently developing. Building the lower field magnet was intended to de-risk working towards the higher field magnet, in which aspects such as higher force or greater homogenization are more challenging.

“The 1.2 GHz can be used for similar applications as the 1.1 GHz,” Bruker noted. “We expect that this additional step forward in signal dispersion, i.e., how far individual peaks are separated in an NMR spectrum from each other, and expected increase in signal-to-noise ratio obtained in NMR experiments will deliver new insights in biological functions and solve chemical questions, as well help in understanding material properties better than it is currently possible.

“The 1.2 GHz prototype is currently being assembled and testing will start soon, followed by a second system later this year. At this time, it is too early to say with confidence when the first 1.2 GHz system will be delivered.”

The Magnetic Resonance Center and Department of Chemistry at the University of Florence is expected to receive the first 1.2 GHz spectrometer. Bruker has received orders for a total of nine 1.2 GHz systems, so far all in Europe.

Leave a Reply

Your email address will not be published. Required fields are marked *