Using softer X-ray absorption spectroscopy to probe biological systems

Abstract

Many inorganic species are now recognized as being essential for life, including many forms of sulfur, phosphate and numerous classes of metal ions. For example, recent progress in the fields of biochemistry and biology has pointed out the critical importance of sulfur in the biosynthesis of vital cofactors and active sites in proteins, and in the complex reaction mechanisms often involved. Special attention has also been drawn to the diverse roles of alkaline (Na(+), K(+)) and alkaline earth (Mg(2+), Ca(2+)) metal ions in mediating the activity of RNA, proteins and many processes in living cells. While the general effect of these ions in biology is mostly understood, information on their detailed role is deficient. Here the application of softer X-ray absorption spectroscopy (XAS) to probe the local structural and electronic environment of such ions within their biological complexes and during physiological reactions is discussed. In addition, the required experimental set-up and the difficulties associated with conducting softer XAS experiments on biological samples are presented.

Nanoscale study of As biomineralization in an acid mine drainage system

“…Studies of As speciation by X-ray absorption spectroscopy techniques are usually performed at the K-edge around 11,872 ± 3 eV (e.g., Morin et al, 2003;Cances et al, 2005;Thoral et al, 2005;Polizzotto et al, 2006). However, studies of As-containing materials at the As L 2,3 -edge ($1330 eV) are possible but rare (e.g., Akabayov et al, 2005). Here we show that this edge provides unambiguous information on As redox state in the Carnoulès AMD samples.…”

Performance and capabilities of the Canadian Dragon: The SGM beamline at the Canadian Light Source

“…As a result, there are relatively few studies of materials in this region, although there are many potentially important edges, particularly for environmental and biological samples [8]. The Canadian Dragon has been designed to provide high flux with good resolution in this range [2].…”

Pyrovanadolysis, a Pyrophosphorolysis-like Reaction Mediated by Pyrovanadate, Mn2+, and DNA Polymerase of Bacteriophage T7

“…X-ray absorption spectroscopy allows detection of changes in the metal sites of metalloenzymes during the course of an enzymatic reaction (19). The binding of a substituted metal cofactor in the Mg 2ϩ -binding site of an enzyme was demonstrated previously for the RNA helicase DbpA (20) and T7 DNA polymerase (21).…”