X-Ray Absorption Spectroscopy in Sulfur Biochemistry
Summary
X-Ray Absorption Spectroscopy (XAS) has become an indispensable tool for probing the chemical environment of sulfur in biological systems. By measuring the absorption of X-rays as a function of energy around the sulfur K-edge, researchers can determine oxidation states, coordination geometries and electronic structure with element specificity. Two principal regimes of XAS, X-ray Absorption Near Edge Structure (XANES) and Extended X-ray Absorption Fine Structure (EXAFS), yield complementary information: XANES is sensitive to oxidation state and local symmetry, while EXAFS provides interatomic distances and coordination numbers. In biochemical contexts, these methods enable characterisation of metal–sulfur clusters in enzymes, identification of post-translational modifications, monitoring of redox switches and elucidation of the speciation of sulphur-containing metabolites. Such insight supports mechanistic enzymology, drug-target validation and the design of bioinspired catalysts. Beyond proteins, XAS also informs on the distribution of sulphur species in tissues, environmental samples and plant materials, thus bridging molecular detail and practical applications in biotechnology, medicine and ecology.
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X-Ray Absorption Spectroscopy in Sulfur Biochemistry publication trend
The graph below shows the total number of articles in x-ray absorption spectroscopy in sulfur biochemistry across all publications each year (not limited to Nature Index journals).
Technical terms
X-ray Absorption Spectroscopy (XAS): Measurement of how X-ray absorption by an element varies with photon energy to reveal local atomic structure.
X-ray Absorption Near Edge Structure (XANES): The region close to the absorption edge sensitive to the oxidation state and coordination geometry of the absorbing atom.
Extended X-ray Absorption Fine Structure (EXAFS): Oscillatory modulations beyond the edge that provide quantitative information on neighbouring atom distances and numbers.
K-edge: The absorption threshold energy at which a core 1s electron is excited, characteristic of each element and its chemical state.
NOS bridge: A redox-sensitive covalent linkage between a lysine nitrogen and a cysteine sulphur via an S–O bond in proteins.
References
- XANES reference library of sulphur-containing compounds for biological research: a status report from the ASTRA beamline at the SOLARIS National Synchrotron Radiation Centre. RSC Advances (2025).
- In Solution Identification of the Lysine–Cysteine Redox Switch with a NOS Bridge in Transaldolase by Sulfur K‑Edge X‑ray Absorption Spectroscopy. The Journal of Physical Chemistry Letters (2024).
- Application of X-ray Spectroscopic Techniques to Determine the Inorganic Composition and Sulfur Chemical Speciation of the Amazonian Plant Bixa orellana. Applied Sciences (2024).
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