Related Experiment Video
Updated: Jun 19, 2026

Detection of Nitric Oxide and Superoxide Radical Anion by Electron Paramagnetic Resonance Spectroscopy from Cells using Spin Traps
Published on: August 18, 2012
Understanding the influence of the protein environment on the Mn(II) centers in Superoxide Dismutases using
Leandro C Tabares1, Jessica Gätjens, Sun Un
1Leiden Institute of Chemistry, Leiden University, 2333 CC Leiden, The Netherlands.
Abstract:
One of the most puzzling questions of manganese and iron superoxide dismutases (SODs) is what is the basis for their metal-specificity. This review summarizes our findings on the Mn(II) electronic structure of SODs and related synthetic models using high-field high-frequency electron paramagnetic resonance (HFEPR), a technique that is able to achieve a very detailed and quantitative information about the electronic structure of the Mn(II) ions. We have used HFEPR to compare eight different SODs, including iron, manganese and cambialistic proteins. This comparative approach has shown that in spite of their high structural homology each of these groups have specific spectroscopic and biochemical characteristics. This has allowed us to develop a model about how protein and metal interactions influence protein pK, inhibitor binding and the electronic structure of the manganese center. To better appreciate the thermodynamic prerequisites required for metal discriminatory SOD activity and their relationship to HFEPR spectroscopy, we review the work on synthetic model systems that functionally mimic Mn-and FeSOD. Using a single ligand framework, it was possible to obtain metal-discriminatory "activity" as well as variations in the HFEPR spectra that parallel those found in the proteins. Our results give new insights into protein-metal interactions from the perspective of the Mn(II) and new steps towards solving the puzzle of metal-specificity in SODs.
More Related Videos
Related Concept Videos
Electron Paramagnetic Resonance (EPR) Spectroscopy: Organic Radicals
π Electron Effects on Chemical Shift: Overview
Electron Transport Chain: Complex III and IV
Colors and Magnetism
When atoms or molecules absorb light at the proper frequency, their electrons are excited to higher-energy orbitals. For many main group atoms and molecules, the absorbed photons are in the ultraviolet range of the electromagnetic spectrum, which cannot be detected by the human eye. For coordination compounds, the energy difference between the d orbitals often allows photons in the visible range to be absorbed and emitted, which is seen as colors by the human eye.
Crystal Field Theory - Octahedral Complexes
To explain the observed behavior of transition metal complexes (such as colors), a model involving electrostatic interactions between the electrons from the ligands and the electrons in the unhybridized d orbitals of the central metal atom has been developed. This electrostatic model is crystal field theory (CFT). It helps to understand, interpret, and predict the colors, magnetic behavior, and some structures of coordination compounds of transition metals.
CFT focuses on...
NMR Spectroscopy: Spin–Spin Coupling

