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Nuclear Magnetic Resonance (NMR) Spectroscopy of Metallobiomolecules

  1. Kara L. Bren

Published Online: 15 DEC 2011

DOI: 10.1002/9781119951438.eibc0296

Encyclopedia of Inorganic and Bioinorganic Chemistry

Encyclopedia of Inorganic and Bioinorganic Chemistry

How to Cite

Bren, K. L. 2011. Nuclear Magnetic Resonance (NMR) Spectroscopy of Metallobiomolecules. Encyclopedia of Inorganic and Bioinorganic Chemistry. .

Author Information

  1. University of Rochester, Rochester, NY, USA

Publication History

  1. Published Online: 15 DEC 2011

Abstract

Nuclear magnetic resonance (NMR) spectroscopy provides information on the structure and dynamics of metallobiomolecules at atomic resolution. A range of metal-binding sites in biomolecules can be studied by NMR, although the methods used require consideration of the properties of the metal site. Diamagnetic metal-binding sites are probed using conventional NMR approaches appropriate for analyzing interactions between ions and macromolecules. Weak metal binding as is common in RNAs may require use of mimics that bind more strongly and/or that provide a specific spectroscopic handle. Paramagnetic metals induce hyperfine shifting and linebroadening that serve as signals of metal binding, but may also require adjustments to standard NMR methodologies. Hyperfine shifting takes place through scalar or dipolar mechanisms, and these effects in turn reveal details of metal site structure and metal electronic structure. Paramagnetic effects on chemical shifts are also used to refine structures of metallobiomolecules. Resonance broadening resulting from the hyperfine interaction is related to unpaired electron–nucleus distance as well as properties of the metal ion and thus can be a restraint on structure. The high magnetic anisotropy of some paramagnetic biomolecules can cause the molecule to take a preferential orientation within the applied magnetic field to allow observation of residual dipolar couplings, which reveal relative angular orientations of bond vectors. The study of the many effects of paramagnetic centers on NMR spectra has advanced the field of biomolecular solution structure determination as these efforts have introduced new restraints used in calculating structures. NMR is also valuable for analyzing biomolecule dynamics and chemical exchange processes. A related application is analysis of interactions between metallobiomolecules and ligands, or other macromolecules. Application of NMR to metallobiomolecules has provided a means to study phenomena difficult to observe using other methods such as interactions between proteins, electron self-exchange reactions, and biomolecule dynamics over a wide range of time scales. NMR methodology continues to advance rapidly and is expected to continue to exert a large influence on our understanding of metal sites in biomolecules.

Keywords:

  • paramagnetic;
  • hyperfine interaction;
  • contact shift;
  • pseudocontact shift;
  • relaxation;
  • residual dipolar coupling;
  • biomolecule structure;
  • biomolecule dynamics