Phase Diagrams as a DOE Tool in Biomolecular Crystallization

Area of Science:

• Biochemistry and Biophysics
• Crystallography
• Chemical Engineering

Background:

• Protein crystallization is crucial for structural biology but presents unique challenges compared to small molecules.
• Heterogeneity in protein crystals, pH fluctuations, and hydrodynamic conditions complicate phase diagram determination.

Purpose of the Study:

• To describe the methodology and theoretical background for establishing crystallization phase diagrams of biomolecules, focusing on proteins.
• To elucidate the mechanisms behind challenges in protein crystallization phase diagram determination.
• To provide guidance for quantifying these effects and establishing accurate phase diagrams.

Main Methods:

• Theoretical analysis of factors influencing protein crystallization phase diagrams.
• Discussion of experimental procedures for phase diagram determination.
• Quantification of effects from water uptake, pH drift, and stirring.

Main Results:

• Water uptake alters equilibrium concentrations and phase diagram boundaries.
• pH drift due to protein dissociation disturbs crystallization equilibrium.
• Stirring conditions impact crystalline phase formation and phase diagram boundaries.

Conclusions:

• Understanding and quantifying water uptake, pH drift, and hydrodynamic conditions are essential for accurate protein crystallization phase diagrams.
• Adequate experimental procedures are necessary to overcome these challenges.
• Accurate phase diagrams are critical for optimizing protein crystallization conditions and locating the crystallization window.