title: The HN(COCA)HAHB NMR experiment for the stereospecific assignment of Hbeta-protons in non-native states of proteins.
abstract: (3)J(H(alpha),H(beta))-coupling constants deliver precious information on the population of the three favored chi(1)-rotamers in unfolded states of proteins. Here, a novel pulse sequence, tailored toward the NMR analysis of non-native states of proteins, the HN(COCA)HAHB experiment, is developed to measure (3)J(H(alpha),H(beta)). In four subsequent INEPT steps, magnetization is transferred from H(N) to H(alpha). In a COSY-like magnetization transfer step, dephasing of magnetization on H(alpha) is quantified to determine the (3)J(H(alpha),H(beta))-coupling constants. Analysis of the measured homonuclear coupling constants, together with measurement of heteronuclear (3)J(N,C(gamma))- and (3)J(C',C(gamma))-coupling constants, allows stereospecific assignment of the two diastereotopic H(beta)-protons even in unfolded states of proteins, and the derivation of populations according to a Pachler-type analysis.
authors.affiliation: Center for Biomolecular Magnetic Resonance, Institute of Organic Chemistry and Chemical Biology, Johann Wolfgang Goethe-University Frankfurt, Max-von-Laue-Strasse 7, D-60438 Frankfurt/Main, Germany.
authors.forename: Martin J
authors.initials: MJ
authors.lastname: Hähnke
authors.forename: Christian
authors.initials: C
authors.lastname: Richter
authors.forename: Friederike
authors.initials: F
authors.lastname: Heinicke
authors.forename: Harald
authors.initials: H
authors.lastname: Schwalbe
mesh_terms: D009682:Magnetic Resonance Spectroscopy; D011487:Protein Conformation; D011506:Proteins / Q000737:chemistry*; D011522:Protons; D013237:Stereoisomerism
chemical_list: D011506:Proteins; D011522:Protons