Quantitative analysis of photoreduction process in Cu metalloproteins

X-ray spectroscopy is an extremely strong tool for metal speciation at the molecular level in biological and environmental samples, especially for metalloproteins. When samples are quite easily influenced by photoreduction, however, analysis has not been straightforward. Recently, a Chinese group has studied in detail soft X-ray induced photoreduction in organic Cu(II) compounds. The research team measured XANES spectra at Cu-LIII, O-K, and C-K edges to see how the valence state of Cu changes. A scanning transmission X-ray microscopy was also employed to look at specific radiation damages. It was found that reducing the radiation dose to 0.1 MGy effectively prevented the photoreduction of organic Cu(II) compounds. For more information, see the paper, "Soft X-ray Induced Photoreduction of Organic Cu(II) Compounds Probed by X-ray Absorption Near-Edge (XANES) Spectroscopy", J. Yang et al., Anal. Chem., Article ASAP (DOI: 10.1021/ac201622g Publication Date (Web): August 1, 2011).