NMR Spectroscopy Resources:
High Resolution Nuclear Magnetic Resonance Spectroscopy is a heavily utilized technique for determining atomic connectivity within a molecule or extended solid, and can be used to assess 3D molecular structure, molecular dynamics, reaction kinetics, ligand binding and docking, and other applications. Before compounds can be tested for biological activity, used in an electronic device, or employed in any other application, synthetic chemists must confirm the exact structure, including chirality, of newly synthesized compounds. NMR is a non-destructive technique that provides critical structural information about new compounds. The figure below shows an example where NMR is used to assign a chemical structure for a model compound used to improve MRI sensitivity and enable early cancer detection [Urbanczyk-Pearson et. al., Mechanistic Investigation of b-Galactosidase-Activated MR Contrast Agents. 2008 Inorganic Chemistry, 47, 56-68].
The magnetic field of an NMR instrument is typically described by the resonance frequency of hydrogen atoms within the magnet; thus, a 14 Tesla magnet is part of a 600 MHz NMR system. Increasing the magnetic field of an instrument increases its sensitivity, reduces the time required to acquire data, enhances the ability to analyze complex compounds, and raises the cost of operation. IMSERC employs multiple instruments with different field strengths to allow simple or crude mixtures to be analyzed immediately on lower cost instruments while more complex experiments are performed on higher field instruments. Analyses can be performed on as little as 0.5 mg of sample and are typically performed using >10 mg. Further, the range of NMR experiments available to IMSERC users is determined by the types of probes available to them. Certain probes are optimized for particular sorts of work; for example, a "broadband" probe is best for detecting non-hydrogen nuclei, whereas an "inverse" probe is best for detecting hydrogens. IMSERC's size allows it to maintain instruments with different types of probes, which enables users to walk in and use the best spectrometer for their needs without reconfiguring hardware.
The entire fleet of NMR instruments available for open-access use is housed in IMSERC. The Structural Biology core facility maintains a 600 MHz instrument with an HCX cryoprobe and is also located in IMSERC space. IMSERC maintains a fleet of five liquids probe-equipped NMR systems at a variety of field strengths and a single 400 MHz wide-bore instrument dedicated to solid-state studies. An overview of open-access NMR instrumentation is shown in below. IMSERC has actively invested in upgrades to the small molecule capabilities through the recent purchase of a Bruker Avance III 600 MHz system and upgrade of an existing 500 MHz magnet with an Avance III console and a direct CH cryoprobe, and upgrades to the probe fleet for the other spectrometers. These advanced capabilities have dramatically improved the data quality and accessibility of more advanced pulse sequences, such as solvent suppression experiments combined with pulsed-field gradient NOESY or ROESY and selective excitation experiments such as 1D NOE which are now carried out routinely on IMSERC systems.
Console /Magnet |
Probes |
Primary Experiment |
User Rates / hr (day/night) |
AVANCE III 600 MHz |
Broadband and Inverse |
Macromolecular Chemistry |
$13 / $5 |
AVANCE III 500 MHz |
Direct CH |
Final Products Characterization |
$15 / $15 |
INOVA 500 MHz |
Inverse HC / |
Walk up 1H / COSY |
$13 / $5 |
“Mercury 400” |
Broadband |
Variable Temperature |
$8 / $5 |
INOVA 400MHz |
Broadband |
Education / Walkup HCX 1D |
$8 / $5 |
Solids-400 Mhz |
5 mm pencil |
Solids |
$5 / $5 |
