Contemporary Use of Anomalous Diffraction in Biomolecular Structure Analysis

Area of Science:

• Structural Biology
• Crystallography
• Biophysics

Background:

• Normal X-ray scattering relies on electron density.
• Anomalous scattering, modulated by X-ray resonance with electronic orbitals, precisely identifies atomic species.
• Anomalous scattering enables multi-wavelength anomalous diffraction (MAD) and single-wavelength anomalous diffraction (SAD) methods.

Purpose of the Study:

• To focus on the prevailing single-wavelength anomalous diffraction (SAD) method for de novo structure determination of biological macromolecules.
• To describe anomalous phasing theory and available phasing elements for SAD experiments.
• To discuss optimization of anomalous signals for challenging applications and their use as molecular markers.

Main Methods:

• Description of anomalous phasing theory.
• Presentation of a periodic table of phasing elements for SAD experiments, distinguishing between at-resonance and off-resonance elements.
• Outline of procedures for current SAD phasing experiments and optimization strategies.

Main Results:

• Detailed explanation of anomalous scattering principles and their application in SAD.
• Identification of suitable elements and experimental conditions for effective SAD phasing.
• Methods for utilizing anomalous signals as molecular markers for tracing and element identification.

Conclusions:

• Single-wavelength anomalous diffraction (SAD) is a predominant method for determining biological macromolecular structures.
• Understanding anomalous scattering and element properties is key to successful SAD experiments.
• Emerging developments promise further advancements in SAD applications and anomalous signal utilization.