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Magic-angle spinning NMR of cold samples

Magic-angle spinning NMR of cold samples
Magic-angle spinning NMR of cold samples
Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin.

In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module).

We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage.

Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature.
0001-4842
Concistrè, Maria
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Johannessen, Ole G.
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Carignani, Elisa
3a8c1dbd-40f8-41cd-9798-937697f19a8b
Geppi, Marco
07ceea31-f76b-4e8b-924c-ea6c2b6a0c43
Levitt, Malcolm H.
bcc5a80a-e5c5-4e0e-9a9a-249d036747c3
Concistrè, Maria
4d926227-2c26-489b-ac6c-ccc1354c68db
Johannessen, Ole G.
799ccc8c-a2e7-4305-a03a-2dc9f42564ef
Carignani, Elisa
3a8c1dbd-40f8-41cd-9798-937697f19a8b
Geppi, Marco
07ceea31-f76b-4e8b-924c-ea6c2b6a0c43
Levitt, Malcolm H.
bcc5a80a-e5c5-4e0e-9a9a-249d036747c3

Concistrè, Maria, Johannessen, Ole G., Carignani, Elisa, Geppi, Marco and Levitt, Malcolm H. (2013) Magic-angle spinning NMR of cold samples. Accounts of Chemical Research. (doi:10.1021/ar300323c).

Record type: Article

Abstract

Magic-angle-spinning solid-state NMR provides site-resolved structural and chemical information about molecules that complements many other physical techniques. Recent technical advances have made it possible to perform magic-angle-spinning NMR experiments at low temperatures, allowing researchers to trap reaction intermediates and to perform site-resolved studies of low-temperature physical phenomena such as quantum rotations, quantum tunneling, ortho-para conversion between spin isomers, and superconductivity. In examining biological molecules, the improved sensitivity provided by cryogenic NMR facilitates the study of protein assembly or membrane proteins. The combination of low-temperatures with dynamic nuclear polarization has the potential to boost sensitivity even further. Many research groups, including ours, have addressed the technical challenges and developed hardware for magic-angle-spinning of samples cooled down to a few tens of degrees Kelvin.

In this Account, we briefly describe these hardware developments and review several recent activities of our group which involve low-temperature magic-angle-spinning NMR. Low-temperature operation allows us to trap intermediates that cannot be studied under ambient conditions by NMR because of their short lifetime. We have used low-temperature NMR to study the electronic structure of bathorhodopsin, the primary photoproduct of the light-sensitive membrane protein, rhodopsin. This project used a custom-built NMR probe that allows low-temperature NMR in the presence of illumination (the image shows the illuminated spinner module).

We have also used this technique to study the behavior of molecules within a restricted environment. Small-molecule endofullerenes are interesting molecular systems in which molecular rotors are confined to a well-insulated, well-defined, and highly symmetric environment. We discuss how cryogenic solid state NMR can give information on the dynamics of ortho-water confined in a fullerene cage.

Molecular motions are often connected with fundamental chemical properties; therefore, an understanding of molecular dynamics can be important in fields ranging from material science to biochemistry. We present the case of ibuprofen sodium salt which exhibits different degrees of conformational freedom in different parts of the same molecule, leading to a range of line broadening and line narrowing phenomena as a function of temperature.

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e-pub ahead of print date: 14 March 2013
Organisations: Magnetic Resonance

Identifiers

Local EPrints ID: 352480
URI: https://eprints.soton.ac.uk/id/eprint/352480
ISSN: 0001-4842
PURE UUID: bf3e7d34-eb04-47cf-884e-3239797b573c
ORCID for Malcolm H. Levitt: ORCID iD orcid.org/0000-0001-9878-1180

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Date deposited: 14 May 2013 13:12
Last modified: 20 Jul 2019 01:06

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