Protein crystals can be incommensurately modulated
Modulated crystals result in diffraction patterns consisting of main reflections surrounded by satellite reflections. These patterns are typically encountered in small-molecule structures at the interface of a phase transition. If the modulation is incommensurate then the satellite reflections cannot be predicted with a supercell. In these cases a superspace indexing approach is used to index the reflections. We report a successful superspace indexing of an incommensurately modulated crystal of profilin:actin. In this case the modulation is induced with a pH change.
Jeffrey J. Lovelace, Cameron R. Murphy, Lee Daniels, Kartik Narayan, Clarence E. Schutt, Uno Lindberg, Christer Svensson and Gloria E.O. Borgstahl