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Figure 1.
Figure 1
Estimated anomalous diffraction ratio [Delta] F/F in the wavelength range 0.5-3.0 Å
for the ten model systems described in this paper. The estimate is for zero scattering
angle and assumes resolved and independent anomalous scatterers. The ten systems are
separated into two groups (Xe group and P/S/Ca group) and sorted in decreasing strength of
the anomalous signal. Black lines, ConA-Xe, adaptin-Xe, PPE-Xe and HEL-Xe; blue line,
thermolysin; green lines, DNA, HEL, trypsin, thaumatin and PPE-Ca. The experimentally
determined anomalously scattering substructures for the ten systems were (1) ConA-Xe: two
protein S atoms, one Mn2+ and one Ca^2+ ion, both fully occupied, as well as six Xe atoms
with occupancies (q) of 0.40, 0.30, 0.20, 0.15, 0.15 and 0.10; (2) adaptin-Xe: four
protein S atoms and two Xe atoms (q = 0.32 and 0.10); (3) PPE-Xe: ten protein S atoms, one
Xe atom (q = 0.72) and two SO[4]^2- ions (q = 0.70 and 0.50); (4) HEL-Xe: ten S atoms, two
Xe atoms (q = 0.24 and 0.08), the first one being situated on a crystallographic twofold
axis, and eight Cl- ions (q = 0.68, 0.58, 0.52, 0.37, 0.37, 0.34, 0.31 and 0.28); (5) DNA:
eight P atoms; (6) HEL: ten S atoms and seven Cl- ions (q = 0.80, 0.77, 0.70, 0.60, 0.57,
0.37 and 0.25); (7) thermolysin: two protein S atoms, six Ca^2+ ions (q = 1.00, 1.00,
1.00, 1.00, 0.50 and 0.25), one fully occupied Zn2+ ion and two DMSO molecules (q = 0.50
and 0.40); (8) trypsin: 14 protein S atoms, one fully occupied Ca^2+ ion and two partially
occupied Cl- ions (q = 0.40 and 0.25); (9) thaumatin: 17 protein S atoms and (10) PPE-Ca:
ten protein S atoms, one Ca^2+ ion (q = 0.81) and one Cl- ion (q = 0.30).
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