Synchrotron SAXS
data from solutions of
S.aureus PstA with c-di-AMP (cyclic-di-AMP receptor)
in
20 mM Tris, 150 mM NaCl, pH 7.5
were collected
on the
EMBL P12 beam line
at the PETRA III storage ring
(DESY; Hamburg, Germany)
using a Pilatus 6M detector
at a sample-detector distance of 3 m and
at a wavelength of λ = 0.124402 nm
(I(s) vs s, where s = 4πsinθ/λ, and 2θ is the scattering angle).
Solute concentrations ranging between 2.2 and 11 mg/ml were measured
at 10°C.
80 successive
0.045 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.
The low angle data collected at lower concentration were merged with the highest concentration high angle data to yield the final composite scattering curve.
S.aureus PstA in presence of its ligand c-di-AMP (at 99% saturation). PstA binds 3 molecules of c-di-AMP. The affinity is in the range of KD=20 nM, thus no free c-di-AMP is expected.
Cyclic di-AMP: https://pubchem.ncbi.nlm.nih.gov/compound/121513901
s, nm-1
