title: An effective method for the discrimination of motional anisotropy and chemical exchange.
abstract: Analysis of the ratio of transverse and longitudinal relaxation rates (R2/R1) is an approach commonly used for estimation of overall correlation time and identification of chemical exchange in biological macromolecules. However, this analysis fails to distinguish between chemical exchange and motional anisotropy. We describe a simple method for identifying chemical exchange and motional anisotropy using the product, R1R2. In the slow tumbling regime, the R1R2 product results in a constant value that is independent of overall correlation time and motional anisotropy. This analysis provides a simple method for rapidly estimating and dissociating the effects of motional anisotropy and chemical exchange in NMR heteronuclear spin relaxation data. We demonstrate the utility of the method with 15N relaxation data collected on the proteins E. coli ribonuclease H and the trimeric E. coli membrane associated lipoprotein lpp.
authors.affiliation: Department of Biochemistry, Weill Medical College of Cornell University, New York, New York 10021, USA.
authors.forename: Julie M
authors.initials: JM
authors.lastname: Kneller
authors.forename: Min
authors.initials: M
authors.lastname: Lu
authors.forename: Clay
authors.initials: C
authors.lastname: Bracken
mesh_terms: D016880:Anisotropy; D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry*; D004926:Escherichia coli / Q000737:chemistry / Q000201:enzymology; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D016914:Ribonuclease H / Q000737:chemistry*
chemical_list: D001425:Bacterial Outer Membrane Proteins; D016914:Ribonuclease H