Protein crystallography in the soft X-ray region: crystal lifetime and diffraction efficiency

Area of Science:

• Crystallography
• Structural Biology
• Materials Science

Background:

• Phase determination is a critical challenge in protein crystallography.
• Multiwavelength anomalous diffraction (MAD) near absorption edges offers a potential solution.
• Soft X-rays present unique challenges due to increased absorption.

Purpose of the Study:

• To investigate the feasibility of MAD using sulfur and phosphorus K-edges for protein structure determination.
• To analyze the impact of increased X-ray absorption on crystal lifetime in the soft X-ray region.
• To derive analytical expressions for diffraction efficiency and estimate optimal crystal size.

Main Methods:

• Derivation of analytical expressions for diffraction efficiency and normalized diffraction efficiency.
• Theoretical analysis of crystal lifetime under soft X-ray irradiation.
• Estimation of optimum crystal size for diffraction experiments.

Main Results:

• Analytical expressions for diffraction and normalized diffraction efficiency were derived.
• Crystal lifetime in the soft X-ray region is significantly shorter than with harder X-rays.
• An optimum crystal size was estimated for MAD experiments.

Conclusions:

• MAD at sulfur and phosphorus K-edges is a promising technique for protein phase determination.
• Increased X-ray absorption poses a significant challenge, limiting crystal lifetime.
• Optimizing crystal size is crucial for successful data collection in this energy range.