MatchMaps

MatchMaps calculates non-isomorphous difference maps in X-ray crystallography for detecting conformational changes in macromolecules.

Key Features:

• Non-isomorphous difference map calculation: Computes observed difference maps that retain high sensitivity to conformational change without requiring structure refinement of the perturbed state.
• Rescue of poorly isomorphous data: Generates usable difference electron-density maps for crystals with modest changes in unit-cell properties that would render traditional isomorphous difference maps ineffective.
• Artifact correction: Corrects artifacts present in nominally isomorphous difference maps.
• Cross-copy and cross-crystal detection: Extends to detecting differences across copies within the asymmetric unit or across altogether different crystal forms.

Scientific Applications:

• Conformational change detection: Maps structural changes in macromolecules as a function of mutations, ligands, and time with extraordinary sensitivity.
• Mutant analysis: Detects structural differences between crystallographic data sets from mutated macromolecules.
• Ligand binding studies: Identifies conformational changes induced by ligand binding without refining the perturbed structure.
• Time-resolved crystallography: Supports detection of time-dependent structural changes in crystallographic measurements.

Methodology:

MatchMaps implements a generalized procedure for calculating observed difference maps using phases from a chosen reference state combined with observed changes in structure factor amplitudes. The package requires PHENIX and CCP4 software environments.