# Single-Crystal NMR for 17O in Alanine Enantiomers

## TL;DR

This study uses advanced NMR techniques to explore the electronic structure of oxygen atoms in crystalline alanine enantiomers, shedding light on molecular chirality.

## Contribution

The first comprehensive characterization of 17O NMR tensors in alanine enantiomers using single-crystal ssNMR combined with X-ray and DFT.

## Key findings

- Eight magnetically nonequivalent 17O resonances were observed and assigned in alanine enantiomers.
- DFT calculations revealed antisymmetric components of chemical shift tensors previously unobserved.
- The integration of ssNMR, X-ray diffraction, and DFT advanced understanding of molecular chirality in amino acids.

## Abstract

Single-crystal solid-state nuclear magnetic resonance
(ssNMR) spectroscopy,
which enables detailed analysis of the electronic structures of crystalline
molecules, offers a unique opportunity to investigate molecular chiralityan
essential feature with broad implications for understanding the origin
and function of life. In this study, we employ single-crystal ssNMR
spectroscopy, in combination with X-ray diffraction and density functional
theory (DFT) calculations, to examine the electronic structure of 17O nuclei in crystalline forms of alanine enantiomers. Eight
magnetically nonequivalent 17O resonances within the unit
cell were observed and successfully assigned, and their corresponding
NMR tensor parameters were determined. These resonances are comprised
of pairs of chemically distinct oxygens in each of four symmetrically
related sites. The experimental findings were compared with previous
NMR studies as well as with DFT calculations performed in this work.
The DFT results not only supported the assignment of crystallographically
distinct 17O sites but also revealed previously unobserved
antisymmetric components of the chemical shift tensors. This study
presents the first comprehensive characterization of 17O NMR tensors in alanine enantiomers and underscores the power of
integrating single-crystal ssNMR with X-ray diffraction and DFT calculations
to advance our understanding of molecular chirality in amino acids.