Direct methods in protein crystallography.

Area of Science:

• Crystallography
• Structural Biology
• Biophysics

Background:

• Direct methods for phase determination are standard for small molecules but not directly applicable to large macromolecules.
• Macromolecular crystallography relies on techniques like isomorphous replacement and anomalous dispersion.

Purpose of the Study:

• To introduce and define 'direct methods in macromolecular crystallography' as a spectrum of phase determination approaches.
• To discuss recent algebraic and probabilistic studies and their future applicability.
• To explore advanced techniques for macromolecular structure determination.

Main Methods:

• Utilizing two-phase and higher-order-phase invariants.
• Employing heavy-atom techniques for invariant evaluation.
• Applying isomorphous replacement and anomalous dispersion analyses.

Main Results:

• Recent algebraic and probabilistic studies involving isomorphous replacement and anomalous dispersion are discussed.
• Advances in filtering and non-crystallographic symmetry (especially for virus structures) are highlighted.
• Progress in applying linear algebra to multiple-wavelength anomalous dispersion is noted.

Conclusions:

• Direct methods, adapted using phase invariants, offer a viable path for macromolecular structure determination.
• Integration of techniques like filtering and non-crystallographic symmetry enhances structural analysis.
• Future research should focus on refining these advanced methods for complex biological structures.