A 13C Spin-Lattice Relaxation Study of the Effect of Substituents on Rigid-Body Rotational Diffusion in Methylene Chloride Solution and in the Solid State

1994 ◽  
Vol 98 (11) ◽  
pp. 2844-2847 ◽  
Author(s):  
Xiaorong Tang ◽  
Alan J. Benesi
Keyword(s):  
Solid State ◽  
Rigid Body ◽  
Chloride Solution ◽  
Methylene Chloride ◽  
Rotational Diffusion ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Methylene Chloride Solution ◽  
Relaxation Study

Solid-state 2H NMR study of methyl-d3-cobalamin

1998 ◽  
Vol 76 (2-3) ◽  
pp. 423-428 ◽  
Author(s):  
Jennifer R Garbutt ◽  
Gillian R Goward ◽  
Christopher W Kirby ◽  
William P Power
Keyword(s):  
Solid State ◽  
Rotational Diffusion ◽  
Group Analysis ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
H Nmr ◽  
Nmr Study

A solid-state 2H NMR study of methyl-d3-cobalamin has been performed as a function of temperature to provide information concerning the character and energetics of the motion performed by this unique bioorganometallic methyl group. Analysis of the 2H NMR line shape indicates that the methyl group undergoes rapid three-fold rotation, and that the Co-C-2H angle lies between 105.9 and 109.5°. Determination of the spin-lattice relaxation times T1 shows that the relaxation is anisotropic, consistent with a "jumping" motion of the methyl group rather than rotational diffusion. This also provides the activation energy to methyl jumps as 8.3 ± 1.3 kJ/mol. It is proposed that this energetic barrier may be a useful probe of changes in the electronic character of the Co-C bond that accompany the biological role of this molecule in such enzymes as methionine synthase.Key words: cobalamin, solid-state NMR, deuterium NMR, molecular dynamics.

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