EDIA

EDIA computes per-atom electron density support scores for macromolecular structures resolved by X-ray crystallography, enabling quantitative assessment of how well individual atomic positions and molecular fragments are supported by experimental electron density.

Key Features:

• Atomic Electron Density Score (EDIA): Computes a weighted sum over an oversampled electron density grid in proximity to each atom to quantify electron density support for individual atoms.
• Fragment and Molecule Scoring (EDIA_m): Aggregates atomic EDIA scores for small molecules, fragments, or residues using the power mean to produce EDIA_m for larger structural components.
• Integration with Experimental Data: Derives scores from the standard 2fo - fc electron density map together with the molecular structure model, accounting for the experimental data and its inherent uncertainties.
• Comparison to Existing Metrics: Provides an alternative to the real-space R correlation coefficient (RSCC) and the real-space difference density Z score (RSZD), and permits direct comparison to experimental density while considering uncertainty, unlike root-mean-squared deviation measures.
• Automated Structure Validation: Enables automated selection and curation of structures based on EDIA scores for high-throughput dataset assembly.
• Model Validation and Method Development: Supplies quantitative, data-aware scores that can be used in model validation and in developing computational methods for molecular design.

Scientific Applications:

• Structure-based molecular design: Uses per-atom and fragment-level EDIA scores to assess the reliability of atomic placements relevant to ligand design and optimization.
• Validation and curation of macromolecular structures: Supports validation and large-scale curation of deposited structures by providing quantitative electron density support measures.
• Computational chemistry and molecular modeling: Facilitates method development and benchmarking by enabling direct, experimentally grounded evaluation of atomic and fragment positions.

Methodology:

Computes a weighted sum over an oversampled electron density grid in proximity to each atom; aggregates atomic scores using the power mean to yield EDIA_m for fragments or molecules; and bases all computations on the standard 2fo - fc electron density map together with the molecular structure model.