The ProteomeLab™ XL-A provides thermodynamic and hydrodynamic information about macromolecules in solution. The computer-controlled system collects absorbance data from sedimentation equilibrium and sedimentation velocity experiments. The XL-A Windows User Interface and Data Analysis Software, included with each ProteomeLab™ XL-I and XL-A, interprets the data to provide information about association states of interacting molecules, association constants, weight average molecular weight, sedimentation and diffusion coefficients and conformation changes. These systems are capable of running up to 21 samples using the appropriate cell assemblies and rotor. Basic hands-on instrument and software training is provided with the purchase of an ProteomeLab™ XL-A or XL-I.