Note that fo and the real part of the anomalous scattering (f ') are colinear, and that f " is 90 degrees phase shifted. Show that the crucial point is the mixing of cos and sin terms and that the little blue arrow to the left does NOT represent a cos term as in normal cases but a sin term ! Hint : f = ( fo+f '+ if ") � (cos(phi) + i sin(phi))
Note that both magnitude of F (and thus, intensity) and phase of F are different for F and -F. Fp = structure factor of protein alone, Fa is real part (both f' and fo) of anomalous scatterer, Fa" is f".
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