Jon Trullinger has finished analyzing the SAXS data on lysozyme pH3.8 in 0 – 40 wt% Choline Dihydrogen Phosphate (CDHP).
Major Conclusions:
1) The presence of CDHP in the buffer eliminates interparticle interference effects on the data. These concentration-dependent effects are indicated by a suppressed intensity at the low Q region and are typically observed for lysozyme at this pH due to Coulombic repulsion between the highly charged lysozyme molecules in solution (note the rollover in the data for the 0% sample (grey) and its absence in the 5 – 40% CDHP data (cyan, 5 wt% CDHP; blue, 10%; purple, 20%; and magenta, 30%).
2) The presence of CDHP in the solution does not affect the overall shape/fold of the protein. Although the intensities of the data are systematically decreased as a result of increasing scattering density of the CDHP-containing solvent (decreased contrast between protein and solvent), the shapes of these curves are similar and predict a globular protein shape that fits well with the crystal structure (see inset of figure). The data are fit to that calculated from pdb no. XXXX and the reduced chi values of these fits are reported.