Cryogenic NMR Probes

Varian has cryogenic nuclear magnetic resonance (NMR) probes for a range of demanding genomics, proteomics and drug discovery and development applications. The probes, cooled using liquid helium, claim a three- to four-fold increase in sensitivity compared to conventional NMR probes. As a result, current experiments can be performed 10-15 times faster, and the scope of compounds that can be analysed is expanded - particularly for those that are available only in minute quantities.

NMR is a non-destructive, information-rich analytical technique helping researchers understand molecular structure, functionality and dynamics. An NMR experiment provides connectivity information - which atoms are attached to which other atoms in a molecule; the spatial orientation of the molecule, such as how it is folded or twisted in three dimensions; as well as the motions within the molecule in its natural environment.

The cryogenically cooled probes will enhance scientists' ability to gather structural information in proteomics/genomics and drug discovery applications. The added sensitivity of the probes will enable faster study of proteins and nucleic acids. The probes will allow the same studies to be performed on proteins that are available in very small quantities or very low concentrations. Previously, NMR could not be used for these experiments.

In addition, using the cryogenic probes could see improvements in metabolite and impurity analyses that are generally performed on very small sample amounts. As well as providing additional sensitivity for traditional sample handling techniques, the unit supports flowing sample capabilities for high throughput liquid chromatography (LC)-NMR analyses that are increasingly common for these applications.

The probes will increase the throughput of general chemical analyses, benefiting a variety of academic and industrial laboratories for which NMR is already a key tool.

An NMR spectrometer consists of a console containing the RF electronics, a computer workstation, a superconducting magnet and the probe. The NMR probe is the device that holds the sample within the bore of the magnet, at the centre of the magnetic field. It contains the antennae that both irradiate the sample with radio frequency energy and receive very weak returning signals that are then analysed to produce structural information. Internally cooling the probe improves sensitivity by increasing the available signal and decreasing the noise arising from electronic components.

This new generation of probes is differentiated from previous models in that they are made from predominantly susceptibility matched metal conductors rather than using High Temperature Superconductor (HTS) structures. Susceptibility matched metal conductors provide better homogeneity and lineshape, basic characteristics of NMR systems that more easily allow the study of molecules in water - of critical importance when investigating proteins in an environment that best approximates real world conditions. In addition, these materials are also more tolerant to moderate and even high salt concentrations, again important in protein and large bio-molecule studies. Varian cryogenic probes offer multiple resonance capabilities and easy shimming, thereby providing a range of capabilities along with straightforward use.