Multi-Wavelength Anomalous Diffraction Using Medium-Angle X-Ray Solution Scattering (MADMAX)  L. Makowski, J. Bardhan, D. Gore, D.J. Rodi, R.F. Fischetti  Biophysical Journal  Volume 102, Issue 4, Pages 927-933 (February 2012) DOI: 10.1016/j.bpj.2012.01.026 Copyright © 2012 Biophysical Society Terms and Conditions

Figure 1 Plots of WAXS patterns calculated with the use of CRYSOL from the atomic coordinate set of myoglobin (1WLA) at the iron edge (dashed) and remote from the edge (solid). The differences generated by the anomalous diffraction from iron represent no more than 1% of the intensity from native myoglobin at any point in the range of observable q-values. Biophysical Journal 2012 102, 927-933DOI: (10.1016/j.bpj.2012.01.026) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 2 Comparison of the predicted and observed anomalous differences from (a) hemoglobin (1IRD) and (b) myoglobin (1WLA), and (c) a reference set from hemoglobin taken at the selenium edge. Differences calculated from atomic coordinate sets (red lines) are compared with differences between intensities at the absorption edge and at ±25 and ±50 eV from the edge (thin black lines). The average of the four anomalous difference curves is plotted as a thick black line. The differences observed at the selenium edge (c) provide a measure of the random and systematic errors in the method, because no selenium was present in the samples. Biophysical Journal 2012 102, 927-933DOI: (10.1016/j.bpj.2012.01.026) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 3 Test of the sphere model with difference intensities computed from atomic coordinate sets using CRYSOL. (a) CRYSOL-generated differences (solid line) compared with the most closely corresponding sphere model (broken line) for hemoglobin. Inset: A space-filling representation of hemoglobin provides a measure of the deviation of the molecule from a spherical shape. (b) Contour plot of the difference between CRYSOL-generated anomalous diffraction and that predicted from a sphere model for hemoglobin obtained using different values of the structural parameters rp and rpa. (c) CRYSOL-generated differences (solid line) compared with the most closely corresponding sphere model (broken line) for myoglobin. The inset shows one view of a space-filling model for myoglobin, demonstrating that its shape is not well represented by a sphere. (d) Contour plot of the difference between CRYSOL-generated anomalous diffraction and that predicted from a sphere model for myoglobin obtained using different values of the structural parameters rp and rpa. In this case, the sphere model fails to achieve a reasonable approximation to the CRYSOL-generated differences. Biophysical Journal 2012 102, 927-933DOI: (10.1016/j.bpj.2012.01.026) Copyright © 2012 Biophysical Society Terms and Conditions

Figure 4 Test of the sphere model with observed difference intensities. (a) Observed differences (solid line) compared with the most closely corresponding sphere model (broken line) for hemoglobin. (b) Contour plot of the discrepancy between the observed difference intensity and the sphere-model difference intensity for hemoglobin as obtained using different values of the structural parameters rp and rpa. (c) Observed differences (solid line) compared with the most closely corresponding sphere model (broken line) for myoglobin. (d) Contour plot of the discrepancy between the observed difference intensity and the sphere-model difference intensity for myoglobin as obtained using different values of the structural parameters rp and rpa. Biophysical Journal 2012 102, 927-933DOI: (10.1016/j.bpj.2012.01.026) Copyright © 2012 Biophysical Society Terms and Conditions