On the assessment of time-resolved diffraction results

Area of Science:

• Crystallography
• Structural Biology
• Biophysics

Background:

• Dynamic structure experiments require metrics to assess data quality and visualize changes.
• Standard crystallographic refinement factors (R1, wR2) are widely used but not directly applicable to time-resolved data.

Purpose of the Study:

• To introduce and evaluate new agreement factors for pump-probe crystallography.
• To demonstrate the utility of Fourier photodifference and photodeformation maps for analyzing structural dynamics.

Main Methods:

• Development of R-factor metrics based on intensity ratios with and without perturbation.
• Application of Fourier photodifference maps to visualize electron density changes.
• Utilizing photodeformation maps to highlight structural alterations.

Main Results:

• R-factors analogous to R1 and wR2 were developed for dynamic crystallography.
• Eta-based R-factors were found to be unsuitable for comparing different datasets.
• Fourier photodifference and photodeformation maps effectively visualize and confirm structural changes.

Conclusions:

• The proposed R-factor metrics provide valuable indicators for dynamic structure analysis.
• Photodifference and photodeformation maps are essential tools for refining and validating models of light-induced structural changes.