Highly diluted proteins

The measurement of highly diluted protein solutions is often required as part of concentration-dependent analyses, e.g. to study binding constants for which it is important to achieve concentrations where both free and complex species are detected and their relative concentrations can be shifted.

Alike highly concentrated protein solutions, also diluted proteins at concentrations below 0.1 g/L are frequently difficult to address with Analytical Ultracentrifugation. In particular, interference detection is no option for the XL-I ultracentrifuge when analyzing proteins below 0.1 g/L.

In contrast, the Aida detector is able to address solute molecules down to a range of 0.01-0.03 g/L. The subsequent figure shows both the raw data and the sedimentation coefficient distribution of 0.02 g/L BSA in PBS buffer. BSA was quantitatively found as monomeric protein with a sedimentation coefficient of 4.29 S.