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Published on: February 11, 2019
The stabilities of protein crystals
1Department of Pharmaceutical Chemistry, University of California at San Francisco, San Francisco, California 94158, USA.
The Journal of Physical Chemistry. B
|March 5, 2010
Summary
This study presents a new model for protein crystallization, explaining how entropy and interactions influence crystal stability. The model accurately predicts how temperature, pH, and salt concentration affect protein crystal formation, aiding in crystallization methods.
Area of Science:
- Biophysics
- Crystallography
- Physical Chemistry
Background:
- Protein crystallization is crucial for structural biology but remains challenging.
- Understanding the thermodynamic principles governing protein crystal stability is essential for optimizing crystallization techniques.
Purpose of the Study:
- To develop a comprehensive thermodynamic model for protein crystallization equilibria.
- To predict protein crystal stabilities based on temperature, pH, and salt concentration.
- To elucidate the mechanisms behind salt-induced stabilization and pH-dependent solubility.
Main Methods:
- Developed a four-term model incorporating translational entropy, contact free energy, and counterion interactions.
- Applied the nonlinear Poisson-Boltzmann equation to treat electrostatic interactions.
- Utilized unit cell information from native protein crystals for boundary conditions.
Main Results:
- The model accurately predicts the stability of lysozyme crystals across varying conditions.
- It explains the weak pH dependence of crystal solubility due to entropic compensation and favorable protein-salt interactions.
- The model predicts nonlinear dependence of solubility on salt concentration, aligning better with experimental data than empirical laws.
Conclusions:
- The developed model provides a robust framework for understanding protein crystallization equilibria.
- It highlights the critical role of counterion translational entropy in salting-out phenomena.
- This model can guide the development of more efficient protein crystallization strategies.
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