A drug-discovery-oriented non-invasive protocol for protein crystal cryoprotection by dehydration, with application...

Area of Science:

• Structural Biology
• Biophysics
• Crystallography

Background:

• Cryoprotection in X-ray crystallography prevents ice crystal formation during rapid cooling.
• Current methods involve high pressure or solvent dehydration.
• Vitrification of solvent to amorphous ice is crucial for crystal preservation.

Purpose of the Study:

• To introduce a novel, non-invasive cryoprotection protocol for macromolecular crystals.
• To reduce the solvent's water fraction via vapor diffusion using a concentrated salt solution.
• To assess the efficacy of this new method for improving crystal quality and data collection.

Main Methods:

• Screening of various salt solutions for optimal cryoprotective properties.
• Development of a vapor diffusion dehydration protocol using 13 M potassium formate (KF13) in the reservoir.
• Application of the KF13 protocol to protein crystals for cryo-cooling and X-ray diffraction analysis.

Main Results:

• Potassium formate (KF13) was identified as an optimal cryoprotectant via vapor diffusion.
• The KF13 protocol effectively reduces the water fraction, promoting vitrification.
• The method proved non-invasive, high-throughput, and beneficial for diffraction resolution and ligand binding studies.

Conclusions:

• Vapor diffusion dehydration with KF13 offers a simple, effective, and non-invasive cryoprotection strategy.
• This protocol is particularly advantageous for large-scale drug discovery projects utilizing fragment libraries.
• The method facilitates the discovery of new crystal hits from screening plates.