Site-specific X-ray triggered photo-oxidation combined with temperature-controlled crystallography can provide a powerful means to reveal structural mechanisms of macromolecular function for cysteine-dependent enzymes.

The enzyme 2,4′-dihydroxyacetophenone dioxygenase (or DAD) catalyses the conversion of 2,4′-dihydroxyacetophenone to 4-hydroxybenzoic acid and formic acid with the incorporation of molecular oxygen. By the use of limited proteolysis, the DAD enzyme from Alcaligenes sp. 4HAP has been crystallized in a form that diffracts synchrotron radiation to a resolution of 2.2 Å.

The observation of O₂ in a time-frozen structure using serial femtosecond rotation crystallography of the as-isolated oxidized enzyme provides long-awaited clear-cut evidence for the mode of O₂ binding in CuNiRs. This provides an insight into how CuNiR from A. xylosoxidans can function as an oxidase, reducing O₂ to H₂O₂, or as a superoxide dismutase (SOD) since it was shown to have ∼56% of the dismutase activity of the bovine SOD enzyme some two decades ago.

The application of softer X-ray absorption spectroscopy (XAS) to biological systems is discussed. In addition, the issues of sample preparation, available beamlines, detection devices and other difficulties associated with conducting softer XAS experiments on dilute biological samples are discussed.

The crystal structure and substrate-binding and activity studies of CYP108D1, an aromatic hydrocarbon-binding cytochrome P450 monooxygenase from N. aromaticivorans DSM12444, are presented.

Simultaneous in situ XAS measurements have been carried out at Au and Pt L₃-edges in order to gain insight into the growth mechanism of Au–Pt core shell nanoparticles.

Rv0864, an enzyme of the Moco biosynthesis pathway from M. tuberculosis, has been overexpressed, purified and crystallized. Diffraction data to 2.5 Å were collected and the structure solved by molecular replacement.

Structures of a new crystal modification of the high-potential iron protein (HiPIP) from C. vinosum and its H42Q mutant have been solved by direct methods and refined anisotropically against data to 1.20 and 0.93 Å, respectively.