Existence of twisting in dislocation-free protein single crystals

Area of Science:

• Crystallography
• Materials Science
• Structural Biology

Background:

• High-quality protein crystal growth is crucial for X-ray diffraction-based structure analysis.
• Perfect, dislocation-free protein crystals are rare, with most exhibiting imperfections.
• Understanding imperfection causes is vital for improving protein crystal quality.

Purpose of the Study:

• To investigate twisting as a cause of imperfection in high-quality protein crystals.
• To analyze twisting in hen egg-white lysozyme crystals using digital X-ray topography.
• To understand the relationship between twisting, crystal growth, and crystal perfection.

Main Methods:

• Employed digital X-ray topography with synchrotron radiation.
• Studied hen egg-white lysozyme crystals exhibiting polymorphisms.
• Quantified twisting magnitude and its variation with crystal size and growth stage.

Main Results:

• Observed twisting magnitudes of 10−6 to 10−5°/μm, significantly smaller than in other materials.
• Twisting was prominent in small crystals and early growth stages, decreasing with crystal size.
• Identified twisting as a primary residual defect influencing overall crystal perfection.

Conclusions:

• Twisting is a significant factor determining the perfection of high-quality protein crystals.
• The handedness of twisting may relate to anisotropic interactions of chiral protein molecules.
• Findings offer insights into protein crystal growth mechanisms and control strategies.