Adaptive Protein Structure Refinement Using Diffraction Data

X-ray crystallography remains the primary technique for discovering the arrangement of a protein’s atoms in space. If this arrangement is given by a vector of atom positions r = (r 1 ,r 2 ,…,r N ), then the resulting structure factor F(r)(S) in direction S is given by where F a ( i ) is the atomic scattering function of a(i) ∈ {“Carbon", “Nitrogen", “Hydrogen",…}, the atom type of the ith atom. F a ( i ) is the Fourier transform of ρ a (i), the spherical electron density for an atom of type a(i) placed at the origin.