title: Protein dynamics studied by rotating frame 15N spin relaxation times.
abstract: Conformational rate processes in aqueous solutions of uniformly 15N-labeled pancreatic trypsin inhibitor (BPTI) at 36 degrees C were investigated by measuring the rotating frame relaxation times of the backbone 15N spins as a function of the spin-lock power. Two different intramolecular exchange processes were identified. A first local rate process involved the residues Cys38 and Arg39, had a correlation time of about 1.3 ms, and was related to isomerization of the chirality of the disulfide bond Cys14-Cys38. A second, faster motional mode was superimposed on the disulfide bond isomerization and was tentatively attributed to local segmental motions in the polypeptide sequence -Cys14-Ala15-Lys16-. The correlation time for the overall rotational tumbling of the protein was found to be 2 ns, using the assumption that relaxation is dominated by dipolar coupling and chemical shift anisotropy modulated by isotropic molecular reorientation.
authors.affiliation: Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, Zürich, Switzerland.
authors.forename: T
authors.initials: T
authors.lastname: Szyperski
authors.forename: P
authors.initials: P
authors.lastname: Luginbühl
authors.forename: G
authors.initials: G
authors.lastname: Otting
authors.forename: P
authors.initials: P
authors.lastname: Güntert
authors.forename: K
authors.initials: K
authors.lastname: Wüthrich
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D007611:Aprotinin / Q000737:chemistry*; D002417:Cattle; D009682:Magnetic Resonance Spectroscopy; D008969:Molecular Sequence Data; D011487:Protein Conformation; D012399:Rotation; D012996:Solutions; D013997:Time Factors
chemical_list: D012996:Solutions; D007611:Aprotinin