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Figure 2
Harker phasing diagrams illustrating the phase ambiguity inherent in SIR phasing (a) and SAD phasing (c), and its resolution by two derivatives in MIR (b) or by SIRAS (d). The `native' amplitude circles (heavy lines) each have radius |FP|. The single isomorphous pair from SIR derivative 1 yields options at Q or R, whereas derivative 2 gives alternatives Q and R′. The anomalous scattering from derivative 1 gives alternatives Q and Q′. Neglecting experimental error, in principle either MIR or SIRAS resolves the phase ambiguity. Adapted from Figs. 4 and 6 of Hendrickson (1981 ![]() |
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