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

Area of Science:

• Bioorganometallic chemistry
• Solid-state nuclear magnetic resonance (NMR) spectroscopy
• Methyl-d3-cobalamin dynamics

Background:

• Cobalamin is a crucial coenzyme in biological systems.
• Understanding the dynamics of the methyl group in cobalamin is essential for elucidating its enzymatic mechanisms.
• Methyl-d3-cobalamin serves as a model compound for studying these dynamics.

Purpose of the Study:

• To investigate the motion and energetics of the methyl group in methyl-d3-cobalamin.
• To determine the Co-C-2H bond angle.
• To characterize the activation energy for methyl group motion.

Main Methods:

• Solid-state 2H NMR spectroscopy was employed.
• Temperature-dependent studies were conducted.
• 2H NMR line shape analysis and spin-lattice relaxation time (T1) measurements were performed.

Main Results:

• The methyl group exhibits rapid three-fold rotation.
• The Co-C-2H angle was determined to be between 105.9 and 109.5 degrees.
• Anisotropic relaxation indicates a
• jumping
• motion, with an activation energy of 8.3 ± 1.3 kJ/mol.

Conclusions:

• The methyl group motion in methyl-d3-cobalamin is characterized by rapid rotation and anisotropic jumps.
• The determined activation energy provides insight into the Co-C bond energetics.
• This energetic barrier may serve as a probe for changes in the Co-C bond during enzymatic catalysis, such as in methionine synthase.