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Updated: May 10, 2026

Atomic Scale Structural Studies of Macromolecular Assemblies by Solid-state Nuclear Magnetic Resonance Spectroscopy
Published on: September 17, 2017
A 13C labeling strategy reveals a range of aromatic side chain motion in calmodulin
Vignesh Kasinath1, Kathleen G Valentine, A Joshua Wand
1Graduate Group in Biochemistry and Molecular Biophysics, University of Pennsylvania Perelman School of Medicine, Philadelphia, Pennsylvania 19104, USA.
Abstract:
NMR relaxation experiments often require site-specific isotopic enrichment schemes in order to allow for quantitative interpretation. Here we describe a new labeling scheme for site-specific (13)C-(1)H enrichment of a single ortho position of aromatic amino acid side chains in an otherwise perdeuterated background by employing a combination of [4-(13)C]erythrose and deuterated pyruvate during growth on deuterium oxide. This labeling scheme largely eliminates undesired contributions to (13)C relaxation and greatly simplifies the fitting of relaxation data using the Lipari-Szabo model-free formalism. This approach is illustrated with calcium-saturated vertebrate calmodulin and oxidized flavodoxin from Cyanobacterium anabaena . Analysis of (13)C relaxation in the aromatic groups of calcium-saturated calmodulin indicates a wide range of motion in the subnanosecond time regime.
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