Issue Date: June 20, 2011
Spinning Improves NMR of Large Proteins
A protein solution continuously spun in a rotor produces a sediment that yields high-quality nuclear magnetic resonance data, providing a new means to determine structures of large proteins, reports a research group led by Ivano Bertini and Claudio Luchinat of the University of Florence, in Italy (Proc. Natl. Acad. Sci. USA, DOI: 10.1073/pnas.1103854108). The approach melds protein ultracentrifugation, a common protein purification technique, with magic-angle spinning, an NMR method used to get structural information about amorphous solids. The team demonstrated the combination using an iron-free form of the iron-storage protein ferritin, which consists of 24 subunits and has a mass of 480 kilodaltons. Data from ultracentrifuged protein solutions match those from crystalline protein samples in both one- and two-dimensional experiments, the researchers show. The ultracentrifugation approach should facilitate study of proteins that are too large for typical solution NMR, they say. It will also enable experiments that are difficult to do with crystals, such as titrations with reagents.
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