Nuclear magnetic resonance (NMR) spectroscopy

Nuclear magnetic resonance (NMR) spectroscopy provides detailed information about the structure, dynamics and the interactions of molecules.

NMR spectroscopy has a wide variety of applications in the study of molecules and molecular processes across many disciplines including chemistry, biochemistry, medicine, pharmacy, physics, engineering, plant biology and soil science, sports science and marine archaeology. NMR spectroscopy uses methodology from which magnetic resonance imaging (MRI) is based.

NMR uses a fundamental property of atomic nuclei to observe nuclei from specific isotopes that are NMR (e.g. ¹H, ¹³C, ¹⁵N, ¹⁹F, ³¹P). This property is spin angular momentum and is usually referred to as 'spin'. Not all isotopes exhibit spin, for example, ¹²C - the most abundant carbon isotope, has a spin of zero and is NMR inactive. This forces NMR practitioners to observe the nuclei from the 1.09% abundant ¹³C isotope.

NUCLEAR:  NMR detects the excitation and relaxation of 'spins' of atomic nuclei from stable isotopes: for example ¹H is the isotope hydrogen that is 99.995% abundant in nature.

MAGNETIC: NMR spectrometers are essentially large radio transceivers that can excite and manipulate the spin angular momentum from an isotope of interest whilst it is residential in a magnetic field.

RESONANCE: The process of resonance provides a transfer of radio frequency based energy to the nuclei of interest to enable direction. 

The power of NMR spectroscopy exists in the wealth of information available from manipulating nuclear 'spins'. The most common piece of information is the chemical shift where chemical environment and structure dictate the positions and nature of NMR peaks in a spectrum. This is used to confirm the bonding arrangement or nature of a chemical compounds or alternatively, it can help solve structures of new compounds, natural products and biomolecules. NMR has powerful applications in monitoring complex mixtures including metabolomics mixtures and can be applied to the study of biological and biomedical processes. This is assisted by the ability of NMR to measure quantitative amounts when set-up correctly.

NMR can also monitor the interaction of molecules at the molecular level.  Interactions between molecules are critical processes and NMR can map and monitor interactions between many molecular types, e.g. metabolites, proteins and pharmaceutical drugs.  NMR spectroscopy has been widely applied in the screening of chemicals to find new compounds across medical applications to be the next generation of medicines. NMR spectroscopy can also interrogate dynamic and motional characteristics of molecules including global and local motions that relate to function and application.

CMCA NMR offers a wide variety of NMR approaches including the following methods listed below:

1. One dimensional spectra - routine ¹H, ¹³C and other nuclei (e.g. ³¹P, ²⁹Si)
2. Multidimensional studies - routine COSY, ¹³C, ¹H- HSQC/HMBC and advanced approaches
3. Biological NMR - peptide, protein, nucleic acids, pathway intermediates, natural products and metabolomics
4. Broadband NMR Experiments: e.g. ⁶Li, ⁷Li, ¹⁵N, ²³Na, ²⁷Al, ²⁹Si, ¹¹³Cd, ¹⁸³W, ¹⁹⁵Pt and ²⁰⁷Pb
5. Solid state NMR (CP-MAS)
6. Diffusion, Dynamics and Variable Temperature studies
7. Structural Determination by NMR

CMCA NMR spectrometers

• Bruker Avance IIIHD 600MHz NMR spectrometer
• Bruker Avance IIIHD 500MHz NMR spectrometer
• Varian 400 MHz NMR spectrometer

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1. One-dimensional spectra

Routine 1D analytical ¹H and ¹³C NMR spectroscopy typically requires 1-20 mg of material dissolved in 0.6 ml of a suitable solvent. ¹³C 1D and DEPT experiments are routine. ³¹P and ¹⁹F NMR spectra of suitable samples can also be obtained. These experiments are available on all UWA spectrometers however, the detection of some nuclei (e.g. ²⁹Si) are optimised for 400, 500 and 600 MHz spectrometers. All NMR experiments can be run qualitative or quantitative; we can advise on the optimum approach for your research or analysis. If you need to run samples in a protonated solvent, we can optimise experiments for solvent suppression to observe your molecule (s) of interest.

2. Multidimensional studies

Multidimensional (nD) NMR experiments enables data simplification and correlation of information to assist in structure conformation/determination and the study of dynamic processes. nD-NMR provides information that can be difficult to obtain from 1D-experiments.

Typical Experiments include: spin-spin coupling correlations (e.g. COSY/TOCSY - adjacent or spin systems ¹H-¹H), through-space correlations (e.g. NOESY/ROESY - structural ¹H-¹H contacts) and ¹H heteronuclear correlations with ¹³C or ³¹P (e.g. HSQC - typically for 1 bond correlations such as C-H and HMBC - for 3-5 bond correlations to H to C or P for long range structural conformation). Advanced and bespoke experimental design is available for specific studies of molecular conformation, interaction and shape. Contact us for more information.

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3. Biological NMR

Solution-state biological NMR spectroscopy applications are available 500 and 600 MHz with each spectrometer providing specific solutions.

500 MHz: biological diffusion, peptide NMR, ligand drug screening
600 MHz: metabolomics, ligand drug screening, peptide NMR, natural products, vitamins and metabolic pathway intermediate analysis, protein triple-resonance (H/C/N NMR), protein interactomics and structural biology.

Capabilities exist at 600 MHz to use 5 mm and 1.7 mm TXI probes with sample volumes of 0.040, 0.250 and 0.650 mL. We can optimize experimentation for your needs including the study of biomolecular interactomics (protein-protein, protein-ligand, protein-DNA, protein-RNA) and biomolecular dynamics cross a variety of timescales: s, ms, s, ns, ps. We can advise on recombinant isotopic enrichment of proteins and peptides in addition to custom designing biological NMR experiments for single samples, detailed projects or larger scale drug/pharmaceutical screening libraries.

Metabolomic experimentation exists at 600 MHz using the 24-sample changer with baseline optimized 1D 1H NMR for profile analysis. Cross validation with 2D TOCSY and HSQC NMR is also available.

Natural product and pathway intermediate analysis (eg. Vitamins and metabolic precursors) analysis is available that can utilize small sample volumes.

Screening experiments include saturation transfer difference (STD), WaterLOGSY, and CPMG. We are specialized in screening and ligand-observe interactions by NMR and although our approaches are 1D 1H optimized, bespoke methods and 2D NMR structure-activity relationships and 19F CPMG screening are also available.

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4. Broadband NMR Experiments

NMR spectra can be recorded for a wide range of nuclei in addition to ¹H, ¹³C, ³¹P and ¹⁹F. However, the ease of measurement of the nuclei can vary dramatically depending on the experiment. Spectra of samples containing the following nuclei have been recorded in our laboratories: ²H, ⁶Li, ⁷Li, ¹¹B, ¹⁵N, ²³Na, ²⁷Al, ²⁹Si, ⁵⁹Co, ⁶³Cu, ⁷⁷Se, ¹¹¹Cd, ¹¹³Cd, ¹¹⁹Sn, ¹³³Cs, ¹⁸³W, ¹⁹⁵Pt and ²⁰⁷Pb.

• Bruker Avance IIIHD 600MHz NMR spectrometer
• Bruker Avance IIIHD 500MHz NMR spectrometer
• Varian 400 MHz NMR spectrometer

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5. Solid state NMR (CP-MAS)

Solid samples typically produce very broad NMR spectra due to significant dipolar broadening that have a dependence to [3cos²0-1] where 0 is the angle between chemical bond vectors and magnetic field. However, if a powdered sample is packed into a rotor and spun at high speed at 54.7^o (where 3cos²0-1=0), a significant increase in the resolution of the spectrum can be obtained. This angle is called the magic angle and the solid NMR approach is magic angle spinning (MAS). ¹³C NMR spectra of solids can be in conjunction with cross-polarisation with ¹H (CPMAS) to produce detailed spectra of solid samples.

• Varian 400 MHz NMR spectrometer

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6. Diffusion, Dynamics and Variable Temperature studies

Diffusion ordered spectroscopy (DOSY) experiments using the 500 MHz DIFF30 probe can determine diffusion coefficients and/or separate data from complex mixtures. Dynamic NMR can also be used to monitor reactions and processes. Nuclear relaxation experiments provide information on molecular size, shape and conformation. Liquid and solid samples can be heated or cooled to study a variety of dynamic processes. Depending on the spectrometer, sample temperature ranges typically exist from -50 to +80°C conditional on solvent and system to be studied. Contact us for more information.

• Bruker Avance IIIHD 600MHz NMR spectrometer
• Bruker Avance IIIHD 500MHz NMR spectrometer
• Varian 400 MHz NMR spectrometer

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7. Structural Determination by NMR

We have computational facilities to provide structural determination of molecules using NMR data. This has been initiated for protein and peptide structural studies but can be expanded to explore the conformation of any molecule of interest in any solvent. Contact us for more details.

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