A Beckman XL-I analytical ultracentrifuge, equipped with absorbance and refractive index detectors, is available for sedimentation velocity and equilibrium measurements. This system can be used to determine molecular weight, sedimentation coefficients, association constants for intermolecular interactions, and a variety of other parameters. High and low temperature GPC systems equipped with multi-angle light scattering detectors are also available. Gel permeation chromatography enables separations of mixtures and polydisperse samples with determination of the concentration and molecular weight of each species using a combination of refractometer, viscometer and multi-angle light scattering detectors. (B-162 Conte, 577-1528, www.pse.umass.edu/ms/)