Abstract:
The interaction between an aromatic ring and divalent sulfur forms an important non-covalent bond for the stability of a protein’s tertiary (folded) structure, such as demonstrated in many common proteins [1]. Recent bioinformatics studies using protein structure databases have revealed that one third of all known proteins have their structure stabilized by such so-called 𝑆⋯𝜋 interactions involving methionine [2]. The medical relevance of this interaction is evident in a number of pathologies, including Alzheimer’s and Creutzfeldt-Jacob's disease. The onset of these diseases is correlated to methionine oxidation or mutation, which in turn leads to structural and functional changes in the related proteins [3]. Many details of this interaction are still undetermined, such as the orientational preference of the sulfur atom with respect to the ring (orthogonal or in plane) and the direction of the sulfur’s lone pair (toward or opposite the ring) [4,5].
In this colloquium, I will present our progress in determining the electronic and geometric structure and derived properties of the 𝑆⋯𝜋 interaction in gas-phase model systems, using both soft X-ray and IR spectroscopic methods.
1. Morgan, R. S., et al., Int. J. Pept. Protein Res. 11, 209–217 (1978).
2. Valley, C. C. et al., J. Biol. Chem. 287, 34979–34991 (2012).
3. Stadtman, Antioxidants and Redox Signaling, 5, 577–582 (2003).
4. Zhou, F et al., New J. Chem. 39, 1611–1618 (2015).
5. Forbes, C.R. et al. , JACS, 139, 1842–1855 (2017).
