Location: NSC 516

Contact: Level III Hyuk-Kyu Seoh ; 404-413-5370

Applications: The XL-A permits a determination of solution molecular weights, association constants, and studies of homogeneity, shape, and other molecular parameters. The instrument consists of a centrifuge and a rotor with a windowed sample compartment, so that the distribution of macromolecules along the radial dimension can be determined at any time by means of an appropriate optical system. Advantages of the analytical ultracentrifuge are 1) that it permits studies of molecules at varying concentrations in many buffers with widely varying salt and pH, and 2) that the conclusions are based directly upon first principles, without the need for standards. Two basic types of experiment are used for rapid estimates of the molecular weight and for determining particle size distributions in a sample: a) using a steady state condition and b) using sedimentation velocity experiment - the speed with which a molecule moves toward the bottom (outermost boundary) of the cell is determined.

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