Introduction:
Jeol ECZ500R Solid-state NMR (SSNMR) spectrometer is a powerful tool to define the supramolecular structure of inorganic-organic hybrids, proteins and polymers; investigate chemical shifts during reactions; and identify the reaction site of different polymers (i.e., pesticides, complexes). The technology is often operating with magic-angle spinning (MAS) techniques, and cross polarization techniques and are particularly useful to analyze the compounds that are insoluble or not suitable to use in solvents. With MAS, polarization from abundant nuclei like 1H, 19F and 31P can be transferred to dilute or rare nuclei, such as 13C, 15N, 29Si to enhance the signal-to-noise ratios and reduce processing time between successive experiments. The equipped instrument in PolyU provides both one- and two-dimensional measurements. The 2D SSNMR measurements include HETCOR, MAS-HMQC and MQMAS. 2D solution-state NMR measurements can also be made and include COSY, NOESY/ROESY, HMQC, HSQC and HMBC. The spectrometer is equipped with a Smart Transceiver System (STS), which is a new technology that achieves high-precision digital radiofrequency, in contrast to the older, conventional NMR systems that use analog technologies.
Applications:
I. Drug Discovery and Design
SSNMR is well suited for studying drug-membrane interactions. The size and insolubility of lipid molecules surrounding the target protein create difficulties for conventional solution-state NMR. Such target membrane proteins could be receptors, channels and transporters embedded in the phospholipid cell membrane, and potential drugs, or ligands, could be small lipophilic molecules (e.g. compounds) or amphiphilic peptides. The amino acid residues within the ligand-binding pocket of the protein target can be elucidated. Identifying ligands that bind weakly to the specific target enables structural optimization to produce potent and high affinity ligands with favorable pharmacological properties. In addition, the pharmacokinetics of drugs (aka ADME – absorption, distribution, metabolism and excretion) depend on drug interactions with lipid membranes. In particular, drug accumulation at membrane surfaces affect pharmacological efficacy by lowering effective concentration and reducing bioavailability.
II. Pharmaceutical Quality Control
Polymorphs of active pharmaceutical ingredients (API) can be characterized. Polymorphs are different crystalline forms of pure drug substances that affect drug properties (e.g. dissolution and bioavailability), formulation, commercial exclusivity and compliance with regulatory agencies. API may convert into different solid forms in response to environmental conditions and exposure to mechanical stress of aging. Despite the presence of excipients (e.g. carrier substances that assist the absorption of the drug or simply add bulk to low dosages) and chiral enantiomer impurities, CP-MAS NMR can confirm the presence of the correct API.
III. Amyloid Fibrils
Amyloid fibrils are insoluble and assembled as high molecular weight protein aggregates that cannot be visualized with the conventional solution-state NMR. Amyloid fibrils are found in amyloid diseases, such as Alzheimer’s disease, and other neurodegenerative disorders, including Parkinson’s disease, Huntington’s disease, type 2 diabetes and transmissible spongiform encephalopathies.
IIII. Polymer Science
The structure, order and dynamics of molecules that compose solids polymers determine their properties, such as impact strength, flexibility and thermal processing. Most polymers are used as solid materials and insoluble in most organic solvents. Dynamics associated with changes in orientations can be studied. Importance of orientation can be exemplified by the large tension strength of fibers due to the parallel orientation of polymer chains along fibers. Contrast agents for MRI (magnetic resonance imaging) or carriers for gene transfer systems are also contained in a polymer (e.g. dendrimer).
V. Inorganic Porous Materials
SSNMR provides detailed structural description in elucidating the interactions of porous frameworks with guest molecules. Zeolites and zeolite-like porous materials and metal organic framework (MOF) contain pores with diameters of several tenths of nanometers to several nanometers and are of interest for applications of ion-exchange, catalysis, separation, gas and heat storage and drug delivery. In particular, ion-exchange and catalysis are investigated for efficient oil refinement. Gas molecules within the materials are separated and stored. Water molecules are also confined to heat storage systems. Drug molecules within drug-delivery systems may be bonded too weakly, leading to uncontrolled release from pores, or bonded too strongly, so that they cannot be released from the pores at required conditions. Detailed investigation of these interactions allows proper control of the strength of bonds between the guest molecules and the framework/porous material.
VI. Liquid-Crystalline Phases
As an intermediate between solids and ordinary isotropic liquids, the rotation motion of molecules is rapid, with nuclear spin interactions averaged, but it is not random, so the averages are different to isotropic liquids, and thus, liquid-crystalline phases can be visualized with a SSNMR.
Charging:
Basic operation: $40 / hr (internal users); $80 / hr (collaborators); $400 / hr (external users)
Booking:
Please visit our University Research Facility Management System (URFMS) website for registration, training request and booking arrangement.
Contact Information:
Location: U003, Block U, The Hong Kong Polytechnic University
Equipment-in-change: Dr. Kenneth Yan (Office: U003)
Email: kenneth.yan@polyu.edu.hk
Telephone: 2766 4690
