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Computer Code for Interpreting 13C NMR Relaxation Measurements with Specific Models of Molecular Motion: The Rigid Isotropic and Symmetric Top Rotor Models and the Flexible Symmetric Top Rotor Model
Technical Report,01 Oct 2013,30 Jun 2016
ARMY EDGEWOOD CHEMICAL BIOLOGICAL CENTER APG MD ABERDEEN PROVING GROUND United States
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Carbon-13 nuclear magnetic resonance 13C NMR spectroscopy is a powerful technique for investigating the motional behavior of molecules in solution. Such investigations commonly include the interpretation of 13C relaxation measurements with specific models of molecular motion. This report describes the fundamental theory and selected results from mathematical modeling programs for three such models, the rigid isotropic and rigid symmetric top rotor models and the flexible symmetric top rotor model, which all have been adopted for interpreting 13C NMR spin-lattice relaxation time T1, spin-spin relaxation time T2, and nuclear Overhauser enhancement factor C measurements. The results for the rigid isotropic rotor illustrate the general behavior of T1, T2, and C as a function of rotational correlation time c. Results for different magnetic field strengths are included to show the dependence of the relaxation values on field strength. The symmetric top rotor results illustrate how the models two correlation times and the orientational dependence of the 13C1H relaxation vector with the symmetric top major axis affect relaxation behavior. Finally, the results of the flexible symmetric top rotor model are presented to reveal how progressively adding internal motion into a symmetric top rotor molecule diminishes this orientational dependence.
APPROVED FOR PUBLIC RELEASE