title: Structure-Free Validation of Residual Dipolar Coupling and Paramagnetic Relaxation Enhancement Measurements of Disordered Proteins.
abstract: Residual dipolar couplings (RDCs) and paramagnetic relaxation enhancements (PREs) have emerged as valuable parameters for defining the structures and dynamics of disordered proteins by nuclear magnetic resonance (NMR) spectroscopy. Procedures for their measurement, however, may lead to conformational perturbations because of the presence of the alignment media necessary for recording RDCs, or of the paramagnetic groups that must be introduced for measuring PREs. We discuss here experimental methods for quantifying these effects by considering the case of the 40-residue isoform of the amyloid β peptide (Aβ40), which is associated with Alzheimer's disease. By conducting RDC measurements over a range of concentrations of certain alignment media, we show that perturbations arising from transient binding of Aβ40 can be characterized, allowing appropriate corrections to be made. In addition, by using NMR experiments sensitive to long-range interactions, we show that it is possible to identify relatively nonperturbing sites for attaching nitroxide radicals for PRE measurements. Thus, minimizing the conformational perturbations introduced by RDC and PRE measurements should facilitate their use for the rigorous determination of the conformational properties of disordered proteins.
authors.affiliation: Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K.
authors.forename: Francisco N
authors.initials: FN
authors.lastname: Newby
authors.affiliation: Department of Life Sciences, Imperial College London , South Kensington, London SW7 2AZ, U.K.
authors.forename: Alfonso
authors.initials: A
authors.lastname: De Simone
authors.affiliation: Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K.|Institute for Integrative Bioscience, National Institutes of Natural Sciences , 5-1 Higashiyama Myodaiji, Okazaki 444-8787, Japan.
authors.forename: Maho
authors.initials: M
authors.lastname: Yagi-Utsumi
authors.affiliation: ICREA and IRB Barcelona , Baldiri Reixac 10, Barcelona 08028, Spain.
authors.forename: Xavier
authors.initials: X
authors.lastname: Salvatella
authors.affiliation: Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K.
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Dobson
authors.affiliation: Department of Chemistry, University of Cambridge , Cambridge CB2 1EW, U.K.
authors.forename: Michele
authors.initials: M
authors.lastname: Vendruscolo
mesh_terms: D016229:Amyloid beta-Peptides / Q000737:chemistry; D004578:Electron Spin Resonance Spectroscopy; D006801:Humans; D064267:Intrinsically Disordered Proteins / Q000737:chemistry*; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular; D010446:Peptide Fragments / Q000737:chemistry; D011487:Protein Conformation; D011994:Recombinant Proteins / Q000737:chemistry; D013113:Spin Labels
chemical_list: D016229:Amyloid beta-Peptides; D064267:Intrinsically Disordered Proteins; D010446:Peptide Fragments; D011994:Recombinant Proteins; D013113:Spin Labels; C078592:amyloid beta-protein (1-40)