Obtaining molecular and structural information from 13C-14N systems with 13C FIREMAT experiments

Area of Science:

• Solid-state Nuclear Magnetic Resonance (NMR) Spectroscopy
• Chemical Physics
• Biophysical Chemistry

Background:

• Dipolar coupling between 13C and 14N nuclei influences solid-state NMR spectra.
• Accurate analysis of these couplings is crucial for determining molecular structure and dynamics.

Purpose of the Study:

• To investigate the effect of 14N dipolar coupling on 13C FIREMAT experiments.
• To develop and validate a method for extracting 13C-14N dipolar and chemical shift tensor information from 13C FIREMAT data.

Main Methods:

• Utilized the full theoretical framework to fit 13C FIREMAT Free Induction Decays (FIDs).
• Required prior knowledge of the electric field gradient (EFG) tensor at the 14N nucleus.
• Applied the method to amino acids (alpha-glycine, gamma-glycine, l-alanine, l-asparagine, l-histidine) at 50 and 100 MHz 13C frequencies.

Main Results:

• The developed method successfully extracted 13C-14N dipolar and chemical shift tensor information.
• Results for alpha-glycine, l-alanine, and l-asparagine showed excellent agreement with existing NMR and neutron diffraction data.
• New data for gamma-glycine and l-histidine were obtained for the first time.
• Assessed the impact of EFG tensor uncertainties on the derived 13C chemical shift and dipolar tensors.

Conclusions:

• The new method provides accurate 13C-14N dipolar and chemical shift tensor information from 13C FIREMAT experiments.
• This approach enhances the structural and dynamic analysis capabilities of solid-state NMR spectroscopy.
• The study validates the method and reports novel tensor values for specific amino acids.