Polarized XAS of Protein and Inorganic Single Crystals at SSRL

M. J. Latimer, B. Hedman

Stanford Synchrotron Radiation Laboratory, SLAC

2575 Sand Hill Road

Menlo Park, CA 94025

Polarized XAS of specifically oriented crystals offers a wealth of molecular and electronic structure information unavailable in un-oriented/isotropic systems. By alignment of molecular vectors to the e-vector of the x-ray beam, specific electronic transitions or EXAFS interactions can be emphasized or minimized. The angle-dependence of the polarized XAS signals allow direct electronic-molecular structure correlations and the precision of XAS distance determinations provide more detailed structural information for metallo-protein active sites than can be provided by crystallography alone.

Development of single crystal XAS instrumentation has been carried out at SSRL on beam line 9-3, the side station on the 16-pole 2T hybrid wiggler beam line 9 dedicated to general user biological XAS. BL9-3 provides high intensity over a broad X-ray energy range, and is designed to provide focused beam from ~5 to 23 keV, and unfocused beam up to ~40 keV and has a pseudo-end station configuration allowing access to both sides of the beam.

Development of single crystal XAS instrumentation, allowing near simultaneous XAS and crystallographic data collection, has been carried out at SSRL BL9-3. A description of the physical setup, design objectives, and examples from recent data collection will be presented.

Developed with support from the DOE, Office of Biological and Environmental Research, and the NIH NCRR Biomedical Technology Program.