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Liquid-like movements in crystalline insulin.
D L Caspar1, J Clarage, D M Salunke
1Rosenstiel Basic Medical Sciences Research Center, Waltham, Massachusetts.
Nature
|April 14, 1988
Summary
Diffuse X-ray scattering reveals protein crystal disorder. Insulin molecules exhibit liquid-like internal movements and correlated lattice vibrations, explaining crystal irregularities.
Area of Science:
- Structural biology
- Crystallography
- Biophysics
Background:
- Diffuse X-ray scattering provides insights into protein crystal disorder.
- Disorder in protein crystals can arise from molecular flexibility and lattice irregularities.
Purpose of the Study:
- To analyze diffuse X-ray scattering patterns from insulin crystals.
- To characterize the nature and extent of disorder in crystalline insulin.
Main Methods:
- Analysis of diffraction patterns from insulin crystals.
- Digital separation of scattering intensity into components.
- Simulation of diffuse scattering using Patterson function and displacement correlations.
Main Results:
- Two types of disorder were identified: liquid-like scattering and haloes around Bragg reflections.
- Internal atomic movements within insulin molecules have root-mean-square (r.m.s.) amplitudes of 0.4-0.45 Å, correlated over ~6 Å.
- Molecular displacements in the lattice have r.m.s. amplitudes of ~0.25 Å, correlated between nearest neighbors.
Conclusions:
- Locally correlated atomic movements within molecules are the primary source of disorder in crystalline insulin.
- Protein molecules exhibit collective motions within the crystal lattice.
- The findings advance the understanding of disorder in protein crystallography.