Protein crystals can be incommensurately modulated

Jeffrey J. Lovelace, Cameron R. Murphy, Lee Daniels, Kartik Narayan, Clarence E. Schutt, Uno Lindberg, Christer Svensson, Gloria E.O. Borgstahl

Research output: Contribution to journalArticlepeer-review

21 Scopus citations


For a normal periodic crystal, the X-ray diffraction pattern can be described by an orientation matrix and a set of three integers that indicate the reciprocal lattice points. Those integers determine the spacing along the reciprocal lattice directions. In aperiodic crystals, the diffraction pattern is modulated and the standard periodic main reflections are surrounded by satellite reflections. The successful indexing and refinement of the main unit cell and q vector using TWINSOLVE, developed by Svensson [(2003). Lund University, Sweden], are reported here for an incommensurately modulated, aperiodic crystal of a profilin:actin complex. The indexing showed that the modulation is along the b direction in the crystal, which corresponds to an 'actin ribbon' formed by the crystal lattice. Interestingly, the transition to the aperiodic state was shown to be reversible and the diffraction pattern returned to the periodic state during data collection. It is likely that the protein underwent a conformational change that affected the neighbouring profilin:actin molecules in such a way as to produce the observed modulation in the diffraction pattern. Future work will aim to trap the incommensurately modulated crystal state, for example using cryocooling or chemical crosslinking, thus allowing complete X-ray data to be collected.

Original languageEnglish (US)
Pages (from-to)600-605
Number of pages6
JournalJournal of Applied Crystallography
Issue number3
StatePublished - Apr 19 2008


  • Actin
  • Incommensurate crystallography
  • Modulated diffraction
  • Modulated protein crystals
  • Profilin
  • Satellite reflections

ASJC Scopus subject areas

  • General Biochemistry, Genetics and Molecular Biology


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