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Correlations of atomic movements in lysozyme crystals
J B Clarage1, M S Clarage, W C Phillips
1Rosenstiel Basic Medical Sciences Research Center, Brandeis University, Waltham, Massachusetts 02254.
Proteins
|February 1, 1992
Summary
Protein crystal disorder is primarily driven by short-range atomic movements, not large-scale vibrations. This finding challenges previous assumptions about crystal dynamics and protein flexibility.
Area of Science:
- Structural biology
- Crystallography
- Biophysics
Background:
- Protein crystals exhibit disorder, impacting diffraction data.
- Understanding atomic motion is crucial for interpreting protein crystal structures.
- Previous models often assumed elastic vibrations or rigid body movements.
Purpose of the Study:
- To investigate the nature of atomic movements in lysozyme crystals.
- To determine the dominant types of atomic motion contributing to diffuse scattering.
- To challenge existing models of protein crystal disorder.
Main Methods:
- Collection of diffuse scattering data from tetragonal and triclinic lysozyme crystals using synchrotron radiation.
- Simulation of diffraction patterns using an exact theory for simple model crystals.
- Relating diffuse scattering intensity to atomic movement amplitudes and correlations.
Main Results:
- Short-range coupled atomic motions dominate, with correlations decaying exponentially (approx. 6 A relaxation distance).
- Tetragonal lysozyme crystals show twice the mean square displacements compared to triclinic.
- Long-range lattice coupled movements contribute minimally (5-10%) to total atomic displacements.
Conclusions:
- Protein crystal disorder is predominantly governed by localized, correlated atomic movements.
- The findings contradict models relying heavily on elastic vibrations or rigid body motions.
- This provides a more accurate picture of protein dynamics in crystalline states.