title: Mesodynamics in the SARS nucleocapsid measured by NMR field cycling.
abstract: Protein motions on all timescales faster than molecular tumbling are encoded in the spectral density. The dissection of complex protein dynamics is typically performed using relaxation rates determined at high and ultra-high field. Here we expand this range of the spectral density to low fields through field cycling using the nucleocapsid protein of the SARS coronavirus as a model system. The field-cycling approach enables site-specific measurements of R (1) at low fields with the sensitivity and resolution of a high-field magnet. These data, together with high-field relaxation and heteronuclear NOE, provide evidence for correlated rigid-body motions of the entire beta-hairpin, and corresponding motions of adjacent loops with a time constant of 0.8 ns (mesodynamics). MD simulations substantiate these findings and provide direct verification of the time scale and collective nature of these motions.
authors.affiliation: Department of Biochemistry and Howard Hughes Medical Institute, MS009 Brandeis University, Waltham, MA 02452, USA.
authors.forename: Michael W
authors.initials: MW
authors.lastname: Clarkson
authors.forename: Ming
authors.initials: M
authors.lastname: Lei
authors.forename: Elan Z
authors.initials: EZ
authors.lastname: Eisenmesser
authors.forename: Wladimir
authors.initials: W
authors.lastname: Labeikovsky
authors.forename: Alfred
authors.initials: A
authors.lastname: Redfield
authors.forename: Dorothee
authors.initials: D
authors.lastname: Kern
mesh_terms: D003198:Computer Simulation; D008958:Models, Molecular; D009010:Monte Carlo Method; D009587:Nitrogen Isotopes / Q000737:chemistry; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D019590:Nucleocapsid Proteins / Q000737:chemistry*; D011487:Protein Conformation; D045473:Severe acute respiratory syndrome-related coronavirus / Q000737:chemistry*
chemical_list: D009587:Nitrogen Isotopes; D019590:Nucleocapsid Proteins