Protein dynamics studied by rotating frame 15N spin relaxation times |
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Authors: | T. Szyperski P. Luginbühl G. Otting P. Güntert K. Wüthrich |
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Affiliation: | (1) Institut für Molekularbiologie und Biophysik, Eidgenössische Technische Hochschule-Hönggerberg, CH-8093 Zürich, Switzerland |
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Abstract: | Summary Conformational rate processes in aqueous solutions of uniformly 15N-labeled pancreatic trypsin inhibitor (BPTI) at 36°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 anistropy modulated by isotropic molecular reorientation.Abbreviations BPTI basic pancreatic trypsin inhibitor - 2D two-dimensional - COSY 2D correlation spectroscopy - TOCSY 2D total correlation spectroscopy - RF radio frequency - CW continuous wave - TPPI time-proportional phase incrementation - CSA chemical shift anisotropy - T1 longitudinal relaxation time - T2 transverse relaxation time - T1 relaxation time in the rotating frame , correlation time for overall rotational reorientation of the protein - exs, exf, correlation times for two conformational exchange processes (slow and fast). |
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Keywords: | Protein dynamics Basic pancreatic trypsin inhibitor Nuclear magnetic resonance spectroscopy Rotating frame spin relaxation times |
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