Figure 1.

Harker diagrams. (a) SIR Harker diagram where H ₁ is the calculated substructure structure factor for the single derivative. The black and red circles have radii given by the observed structure-factor amplitudes for the native and the derivative, respectively. (b) SAD Harker diagram where H ⁺ and H ⁻ are the calculated substructure structure factors and H ⁺ − H ^−* is the expected vector difference between the true structure factors F ⁺ and F ^−*. (c) MIR Harker diagram where H ₁ and H ₂ are the calculated substructure structure factors for the first and second derivatives, respectively. The black, red and blue circles have radii given by the observed structure-factor amplitude for the native, the first derivative and the second derivative, respectively. In the absence of measurement errors and errors in the substructure, the red and blue circles would intersect at one point on the black circle.