PERFORMING TWO WAVELENGTH MAD EXPERIMENT WITHOUT CHANGING ENERGY

Cornell University, Ithaca NY

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. A novel method of performing two wavelength MAD experiment without changing energy was developed. This novel method utilizes the inherent property of a synchrotron storage ring, where multiple harmonic energies are incident from the monochromator. During a typical crystallography experiment, the higher harmonics are considered "undesired" and rejected using a metal coated or un-coated mirror. By appropriate choice of incident energy and mirror surface, we were able to incident two energies (edge and far remote) on a gadolinium soaked Proteinase K crystal and collect a two wavelength MAD dataset. We were also able to show that superior quality electron density maps could be obtained from these MAD experiments as compared to those from a SAD experiment. A manuscript describing this experiment is in preparation.