Protein dance on nanoparticle surface revealed

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.”