X-Ray Spectroscopy
Technique: X-ray Spectroscopy
X-ray Absorption Spectroscopy (XAS) - XAS is an element-specific technique which provides unique information on the local geometric and electronic structure of targeted atoms as well as detailed atomic structure within 5-10 Å of the target. The x-ray absorption spectrum is typically divided into two regimes: x-ray absorption near-edge spectroscopy (XANES) and extended x-ray absorption fine-structure spectroscopy (EXAFS). XANES provides information about the formal oxidation state and coordination chemistry of the absorbing atom, while EXAFS is used to determine the distances, coordination number, and species of the neighbors of the absorbing atom. These data can be generated in solution or solid phase, and are very complementary to other spectroscopic and structural approaches such as X-ray crystallography, X-ray Footprinting, small-angle X-ray scattering (SAXS) and infrared spectroscopy.
X-ray absorption promotes a core-level electron, after which an electron from a more energetic state falls into the core, releasing fluorescent photons according to the absorption probability at a given energy. This probability is determined by interference patterns caused by photo-electron scattering from neighboring atoms, resulting in a complex signature oscillatory pattern which can be analyzed to provide detailed structural information.
Approximately one-third of all proteins require a metal atom for their specific structure and function. These metalloproteins tend to be critical metabolic enzymes in biological systems; XAS can provide valuable information about metal active sites for a detailed understanding of reaction chemistry. The Case Center for Synchrotron Biosciences X3B beamline, located at the National Synchrotron Light Source at Brookhaven National Laboratory, specializes in the spectroscopic study of metalloproteins, and can access absorption edge energies for most biologically relevant metals (3.8-13.3 keV).
Nickel Superoxide Dismutase reaction chemistry. Neupane et al. (2007) J Am Chem Soc 129, 14605.
For more information on the X3B Beamline, click here.
Contact Person:
Jen Bohon, Ph.D. (jbohon@bnl.gov)
National Synchrotron Light Source
Bldg. 725A-X3B
Brookhaven National Laboratory
Upton, NY 11973
Office Location: Building 535, Room 1-A108
Phone: (631) 344-4613
Fax: (631) 344-5594