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13 C spin relaxation studies of the basic pancreatic trypsin inhibitor
Author(s) -
Wüthrich Kurt,
Baumann Rudolf
Publication year - 1976
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270081011
Subject(s) - intramolecular force , chemistry , relaxation (psychology) , trypsin , trypsin inhibitor , crystallography , molecule , globular protein , nuclear magnetic resonance , stereochemistry , enzyme , organic chemistry , physics , psychology , social psychology
The longitudinal 13 C spin relaxation times T 1 and the 13 C{ 1 H} nuclear Overhauser enhancement were measured in a concentrated aqueous solution of the basic pancreatic trypsin inhibitor. The correlation time for overall rotational motions of the basic pancreatic trypsin inhibitor molecules was found to be τ R ≈ 2 × 10 −8 s. In connection with previous 1 H n.m.r. studies of intramolecular motions of the aromatics, we were particularly interested in the correlation times τ G for intramolecular segmental motions of the aromatic rings. The present experiments revealed no manifestation of intramolecular motions of the aromatics, indicating that τ G ≫ 2 × 10 −8 s for the aromatic ring carbon atoms. On the other hand, rapid segmental motions were evidenced for the peripheral carbon atoms of aliphatic amino acid sidechains. Comparison of the 1 H and 13 C n.m.r. data on the basic pancreatic trypsin inhibitor indicates that the time scale of high resolution 1 H n.m.r. at high fields may in many instances be more appropriate for studies of the molecular dynamics in globular proteins than the time scale of spin relaxation measurements.