[RASMB] aggregates data analysis

[Beld, Joris]

Dear all,

I'm spinning a sample which shows -to me- surprising behavior. The raw data of a normal sedimentation equilibrium run of a protein looks always like a half-parabolic curve of the radius versus absorbance (x,y).
However, this particular sample (protein) shows a different behavior in that the raw data look like a straight line taking off halfway the liquid column (absorbance almost zero) in the sector to the bottom of the cell (absorbance 0.7). Same behavior is reproducible at three different concentrations and three different rotational speeds (10,20,30 krpm).
How should I interpret these data? Ultrascan does not really 'like' this data as input (although fitting is possible, the residuals look very bad, the fitted Mw -to a single species- is around 280kDa).
Is this how a heterogeneous aggregating sample should look like?
Thanks in advance.

Best wishes,

Joris Beld
ETH Zürich
Switzerland