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A new complexity in protein chemistry: Algorithm uncovers overlooked chemical linkages

A new complexity in protein chemistry
Representation of a newly discovered nitrogen-oxygen-sulfur, known as NOS, link (blue: nitrogen, red: oxygen, yellow: sulfur) between the amino acids glycine and cysteine within an enzyme. Credit: Sophia Bazzi (structural data from the Protein Data Bank, visualization using Coot software)

Proteins are among the most studied molecules in biology, yet new research from the University of Göttingen shows they can still hold surprising secrets. Researchers have discovered previously undetected chemical bonds within archived protein structures, revealing an unexpected complexity in protein chemistry.

These newly identified nitrogen-oxygen-sulfur (NOS) linkages broaden our understanding of how proteins respond to , a condition where harmful oxygen-based molecules build up and can damage proteins, DNA, and other essential parts of the cell. The new findings are in Communications Chemistry.

The research team systematically re-analyzed over 86,000 high-resolution protein structures from the Protein Data Bank, a global public repository of protein structures, using a new algorithm that they developed inhouse called SimplifiedBondfinder. This pipeline combines , quantum mechanical modeling, and structural refinement methods to reveal subtle that were missed by conventional analyses.

A new complexity in protein chemistry
Illustration of how researchers used their new "SimplifiedBondfinder" algorithm to reveal hidden chemical bonds in proteins. It combines machine learning (UMAP*), quantum mechanical modeling, and structural refinement methods. "*Uniform Manifold Approximation and Projection" is a machine learning algorithm for dimensionality reduction. It was used to project high-dimensional chemical descriptor data into a low-dimensional space, enabling the identification of clusters corresponding to known and new bonds. Credit: Sophia Bazzi (protein structural data from the Protein Data Bank, visualization using Pymol and Coot software)

Unexpectedly, NOS linkages were not restricted to previously known amino acid pairs but were also discovered between the amino acid pairs arginine-cysteine and glycine-cysteine. NOS linkages were first discovered by research led by Professor Kai Tittmann at Göttingen University.

"Our work shows that the Protein Data Bank still holds hidden chemistry," said Dr. Sophia Bazzi at Göttingen University's Institute of Âé¶¹ÒùÔºical Chemistry, who led the study. "By developing new digital tools and revisiting existing data, we uncovered chemical interactions that had remained unnoticed for decades."

These NOS bonds act as molecular switches, stabilizing proteins under oxidative stress and potentially influencing a whole range of biological processes. "Our approach has much wider implications," Bazzi adds. "It can uncover overlooked chemical bonds, leading to improved protein models and advancing protein engineering, drug design, and synthetic biology."

More information: Sophia Bazzi et al, Revealing arginine-cysteine and glycine-cysteine NOS linkages by a systematic re-evaluation of protein structures, Communications Chemistry (2025).

Journal information: Communications Chemistry

Citation: A new complexity in protein chemistry: Algorithm uncovers overlooked chemical linkages (2025, May 20) retrieved 21 May 2025 from /news/2025-05-complexity-protein-chemistry-algorithm-uncovers.html
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