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Scientific Validation Report

This document details the validation of the synth-xtal simulation engine against peer-reviewed experimental data.

Methodology

To verify the accuracy of the Debye-based scattering simulation and the solvent subtraction model, we compare synthetic profiles generated from crystal structures (PDB) against experimental data from the Small Angle Scattering Biological Data Bank (SASBDB).

Assessment Criteria

  • Correlation Coefficient ($\rho$): Calculated on the log-intensity scale (standard for Crystallography) in the primary scattering range ($q < 0.3 \text{ \AA}^{-1}$).
  • Primary Range: $q < 0.3 \text{ \AA}^{-1}$ captures the Guinier regime ($R_g$) and the first few form factor features, which are most sensitive to the overall protein fold.

Validation Results

1. Ubiquitin (Monomer)

2. Lysozyme

Interpretation

The high correlation ($> 0.97$) across different protein folds demonstrates that: 1. Atomic form factors (Waasmaier & Kirfel, 1995) are correctly implemented. 2. Solvent subtraction (Pavlov & Svergun, 1997) accurately models the contrast effect of the displaced water volume. 3. Hydration shell modeling (standard excess density of $0.03 \text{ e/}\text{\AA}^3$) provides a physically grounded improvement to the fit.

The slight deviations from 1.0 correlation are expected due to: * Experimental noise in the SASBDB datasets. * The use of static crystal structures to model proteins that exhibit side-chain and backbone flexibility in solution. * Possible differences in buffer conditions and ionic strength between experiment and simulation.

References

  • Waasmaier, D. & Kirfel, A. (1995). Acta Cryst. A51, 416-431.
  • Pavlov, M.Y. & Svergun, D.I. (1997). J. Appl. Cryst. 30, 712-717.
  • Svergun, D., et al. (1995). J. Appl. Cryst. 28, 768-773.