Standard proteins

Darja Ruskule.

SASDA32 – BSA in HEPES

Serum albumin
MWI(0) 64 kDa
MWexpected 69 kDa
VPorod 97 nm3
log I(s) 5.93×101 5.93×100 5.93×10-1 5.93×10-2
Serum albumin small angle scattering data  s, nm-1
ln I(s)
Serum albumin Guinier plot ln 5.93×101 Rg: 2.9 nm 0 (2.9 nm)-2 s2
(sRg)2I(s)/I(0)
Serum albumin Kratky plot 1.104 0 √3 sRg
p(r)
Serum albumin pair distance distribution function Rg: 2.8 nm 0 Dmax: 9.3 nm

Data validation

Fits and models

log I(s)
 s, nm-1
Serum albumin DAMMIF model
log I(s)
 s, nm-1
Serum albumin NONE model
Synchrotron SAXS data from solutions of BSA in HEPES in 50 mM HEPES 50 mM KCl, pH 7.5 were collected on the EMBL X33 beam line at the DORIS III storage ring (Hamburg, Germany) 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 at 10°C. Eight successive 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.

Serum albumin (BSA)
Mol. type   Protein
Organism   Bos taurus
Olig. state   Monomer
Mon. MW   69.3 kDa
 
UniProt   P02769
Sequence   FASTA
 
PDB code   3V03