The ProteomeLab XL-I analytical ultracentrifuge from Beckman Coulter is designed for in-solution characterization of macromolecules such as proteins, nucleic acids, lipids, polysaccharides, viruses, and nanoparticles. It combines dual detection optics—scanning UV/Vis absorbance and Rayleigh interference—providing high sensitivity across a wide concentration range and eliminating the need for calibration standards. Operating on first-principles thermodynamic and hydrodynamic analysis, the XL-I directly determines molecular weights, stoichiometry, and interaction parameters. Its precise temperature control (approximately 4 °C to 50 °C) allows measurements under native or physiologically relevant conditions, while requiring only small sample volumes. The instrument supports both sedimentation-velocity (SV) and sedimentation-equilibrium (SE) experiments, yielding information on sedimentation and diffusion coefficients, molecular weight, oligomeric state, and binding affinities. Applications span the determination of protein molecular weights and oligomeric states, assessment of sample heterogeneity and aggregation, and quantification of biomolecular interactions—including protein–protein, protein–ligand, and nucleic acid complexes—without labelling or immobilization. Beyond proteins, it is used to study viruses, liposomes, nanoparticles, and polymeric systems.
