title: Measuring 1HN temperature coefficients in invisible protein states by relaxation dispersion NMR spectroscopy.
abstract: A method based on the Carr-Purcell-Meiboom-Gill relaxation dispersion experiment is presented for measuring the temperature coefficients of amide proton chemical shifts of low populated 'invisible' protein states that exchange with a 'visible' ground state on the millisecond time-scale. The utility of the approach is demonstrated with an application to an I58D mutant of the Pfl6 Cro protein that undergoes exchange between the native, folded state and a cold denatured, unfolded conformational ensemble that is populated at a level of 6% at 2.5°C. A wide distribution of amide temperature coefficients is measured for the unfolded state. The distribution is centered about -5.6 ppb/K, consistent with an absence of intra-molecular hydrogen bonds, on average. However, the large range of values (standard deviation of 2.1 ppb/K) strongly supports the notion that the unfolded state of the protein is not a true random coil polypeptide chain.
authors.affiliation: Department of Molecular Genetics, The University of Toronto, Toronto, ON, Canada.
authors.forename: Guillaume
authors.initials: G
authors.lastname: Bouvignies
authors.forename: Pramodh
authors.initials: P
authors.lastname: Vallurupalli
authors.forename: Matthew H J
authors.initials: MH
authors.lastname: Cordes
authors.forename: D Flemming
authors.initials: DF
authors.lastname: Hansen
authors.forename: Lewis E
authors.initials: LE
authors.lastname: Kay
mesh_terms: D006860:Hydrogen Bonding; D008958:Models, Molecular; D019906:Nuclear Magnetic Resonance, Biomolecular / Q000379:methods*; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013696:Temperature
chemical_list: D011506:Proteins; D011522:Protons