Acquisition of an Optima XL-A Analytical Ultracentrifuge

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We are requesting funds from the National Science Foundation to purchase an Analytical Ultracentrifuge. This is to replace our 26-year old Model E ultracentrifuge, which is nearly impossible to maintain and for which certain accessories are no longer produced. Also, the XL-A has greatly increased sensitivity as a result of a very much shorter optical path length and advances in component quality over the last quarter century. Furthermore, its output is now fully computer processed, enabling far more rapid and reliable processing of results. With this instrument, we will be able to obtain molecular weights, effective partial specific volumes and sedimentation constants. These pieces of information will allow us to determine molecular architecture of multisubunit assemblies, more reliably estimate compositions of macromolecular aggregates which are complex and which may interact extensively with solvent constituents, and obtain quantitative parameters of protein association reactions. Specifically, the instrument will be used to obtain "true" (in a thermodynamic sense) molecular weights of cellulase components, metalloenzymes and redox proteins from hyperthermophiles, explore subunit interactions in human choriogonadotropin, measure hydration and salt binding in yeast enolase and measure complex formation between reactants in the bacterial luciferase reaction.