data from solutions of
BSA in HEPES
50 mM HEPES 50 mM KCl, pH 7.5
EMBL X33 beam line
at the DORIS III storage ring
using a Pilatus 1M-W detector
at a sample-detector distance of 2.7 m and
at a wavelength of λ = 0.15 nm
(I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle).
One solute concentration of 25.64 mg/ml was measured
15 second frames were collected.
The data were normalized to the intensity of the transmitted beam and radially averaged; the scattering of the solvent-blank was subtracted.
Bovin Serum Albumin (BSA) is an extremely important protein in Small Angle X-Ray Scattering. It is, in fact, used as standard in order to calculate the molecular weight of other proteins. The reasons why it has been chosen as standard it is because it can be easily stored in its powder form and it is also very well characterised. In solution is present as a monomer-dimer equilibrium, therefore the molecular weight of the standard BSA is not the one of the monomer (68 kDa) but is slightly bigger (72 kDa). The crystal structure of BSA has been solved recently therefore ab initio models can be compared with atomic structure like in this picture.