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Analytical Chemistry

Protein dance on nanoparticle surface revealed

NMR technique glimpses ubiquitin dynamics on nanoparticle

by Stu Borman
May 16, 2016 | A version of this story appeared in Volume 94, Issue 20

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Credit: J. Am. Chem. Soc.
Dynamics of ubiquitin (gray ribbon) on the surface of a lipid nanoparticle show that the protein rotates (red arrow) about an internal rotation axis perpendicular to the surface while wobbling (black double arrow) more rapidly in a cone-shaped volume.
Graphic shows NMR-determined rotation and wobbling motions the protein ubiquitin undergoes on a lipid nanoparticle surface.
Credit: J. Am. Chem. Soc.
Dynamics of ubiquitin (gray ribbon) on the surface of a lipid nanoparticle show that the protein rotates (red arrow) about an internal rotation axis perpendicular to the surface while wobbling (black double arrow) more rapidly in a cone-shaped volume.

The growing use of nanomaterials in biomedical applications makes understanding nanoparticle-protein interactions an important goal. Nuclear magnetic resonance spectroscopy is a promising way to probe such interactions. But because of the huge size difference between nanoparticles and proteins, protein peaks disappear in nanoparticle NMR spectra, making the interactions invisible. G. Marius Clore, Vitali Tugarinov, and coworkers at the National Institute of Diabetes & Digestive & Kidney Diseases have now developed an NMR technique that can image protein dynamics on lipid-based nanoparticle surfaces (J. Am. Chem. Soc. 2016, DOI: 10.1021/jacs.6b02654). They made the advance after recognizing that NMR properties of nanoparticle-bound proteins depend on nanoparticle size. By analyzing changes in NMR “exchange lifetime broadening” when ubiquitin binds different-sized nanoparticles, the researchers found that the protein rotates in microseconds around an internal axis approximately perpendicular to nanoparticle surfaces while wobbling in nanoseconds in a cone centered on the axis. The approach “shows the power of NMR to unravel atomic-level details of protein states,” comments Hanudatta S. Atreya of the Indian Institute of Science. “No other technique can provide this information in such detail.”

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