Reverse Monte Carlo Study of Diffuse Scattering from a Frustrated Protein System

Distinctive diffuse rings around Bragg positions have been observed in the diffraction patterns of a crystal of the N-terminal fragment of the Gag protein from Feline Foamy Virus. It is shown that these are caused by geometric frustration as molecules try to pack on the triangular a–b mesh of the space group P6122. The disorder prohibits conventional structure solution. The possibility of using the diffuse scattering to aid solution is explored using Reverse Monte Carlo modelling.