Beckman XLA

The ProteomeLab XL-A is Beckman Coulter's classic analytical ultracentrifuge, built around a scanning UV/Vis absorbance detector that reads concentration directly through the spinning cell across a 190–800 nm range. Because the detection is absorbance-based, it works best with samples that have a well-defined chromophore — proteins via their 280 nm aromatic absorbance, nucleic acids at 260 nm, or a labelled species at a specific wavelength — and, like all AUC, needs no external calibration standard, since the measurement is derived from first-principles physics rather than a reference curve.

Detection: scanning UV/Vis absorbance, 190–800 nm

Temperature range: 4–20 °C

Mass range accessible: kDa to MDa

No calibration standard required (first-principles measurement)

Single-wavelength absorbance optics per scan

At PINT, the XL-A covers standard absorbance-detected sedimentation velocity and equilibrium runs — the default choice for a well-behaved protein at typical concentrations. For samples that need interference optics (very high concentrations, or species without a strong chromophore) or faster rotor speeds, the newer Optima AUC is used instead.