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Updated: Jul 13, 2026

Site Directed Spin Labeling and EPR Spectroscopic Studies of Pentameric Ligand-Gated Ion Channels
Published on: July 4, 2016
Application of the paramagnetic dipole field for solution NMR active site structure determination in low-spin,
1Department of Chemistry, University of California, Davis, California 95616, USA. lamar@chem.ucdavis.edu
Abstract:
The principles for the application of the paramagnetic dipolar field of low-spin, cyanide-inhibited ferrihemoproteins for determining active site structure are briefly described. The ubiquitous dipolar shifts for assigned residues, together with crystal coordinates of some appropriate structural homolog, allow determination of the orientation and anisotropies of the paramagnetic dipolar tensor. The orientation of chi uniquely defines the orientation of the Fe-CN unit, which is tilted variably and sensitively monitors distal steric and H-bond interactions. The mapped dipolar field, in turn, can be used to determine the orientation of mutated residues. Case studies involving unusual genetic variants and point mutants of myoglobins, human hemoglobins, horseradish peroxidase and its substrate complex of heme oxygenase are presented as examples.
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