Biophysical Society of Canada (BSC)
Société de Biophysique du Canada (SBC)
Farideh JALILEHVAND
University of Calgary
X-ray Absorption Spectroscopy in Natural Sciences; Exploring New Possibilities
Extended X-ray absorption fine structure (EXAFS) spectroscopy is an element-specific technique, providing information on average interatomic distances, the number and chemical identities of near neighbors around absorber. The hydration of the biologically important Ca2+ ion is notoriously difficult to study in solution because of the flexible and dynamic coordination environment. By combining EXAFS results with molecular dynamics simulations we could obtain precise mean Ca-O bond distances, the hydration number, and the geometry of the Ca2+(aq) species. In living organisms the synthesized proteins are translocated across cell membranes. The translocation is catalyzed by the preprotein translocase, where SecA ATPase is a central component. In a recent study on the structure of the zinc-binding domain of Sec A, we could clarify the local zinc site environment by Zn K-edge EXAFS. The zinc atom coordinates two cysteine thiolate groups, an imidazole group of histidine, and a water molecule. X-ray absorption near edge structure (XANES) spectroscopy is a non-destructive technique, giving information on the oxidation state, electronic configuration and bonding of the absorber. By applying sulfur XANES on wooden cores from the 17th century Swedish warship Vasa, we could reveal the cause of high acidity and salt precipitation on the wood (Nature 2002, 415, 893-897). Our results show that large amounts of sulfur in reduced forms within the moist wood are being oxidized to sulfuric acid, which eventually will cause wood degradation. Sulfur XANES spectroscopy can also reveal, on a molecular basis, the effects of sour gas exposure on sulfur metabolism in intact plant leaves.