A multifaceted approach to the interpretation of NMR order parameters: A case study of a dynamic α-helix

Eric Johnson, Scott A. Showalter, Rafael Brüschweiler

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15 Scopus citations


The model-free approach (Lipari, G.; Szabo, A. J. Am. Chem. Soc. 1982, 104, 4546-4559; 4559-4570) is the standard method for the analysis of NMR relaxation data from proteins. The method assigns to each interaction vector a generalized order parameter S2, which is a measure of the spatial restriction that the vector experiences in a molecular reference frame. A variety of techniques for the interpretation of S2 values and their underlying assumptions are tested here for a dynamic α-helix represented by an ensemble of peptide structures that satisfies a set of predefined constraints. A self-consistent picture is developed that characterizes the influence of major determinants, including backbone dihedral angle fluctuations and their correlations, separability of internal and overall motion, the preservation of hydrogen bonds, restricted end-to-end distance fluctuations, locally anisotropic dynamics, and local contacts between interaction vector atoms and their environment. Many of the features parallel experimental NMR and computational observations of helices in proteins. The understanding gained from this model system is expected to contribute toward the ever more detailed interpretation of experimental order parameter profiles.

Original languageEnglish (US)
Pages (from-to)6203-6210
Number of pages8
JournalJournal of Physical Chemistry B
Issue number19
StatePublished - May 15 2008

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films
  • Materials Chemistry


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