Local Resolution

Local resolution estimates rely on comparing independently reconstructed maps with Fourier-based correlations. The correlation measures how consistently spatial frequency information is reproduced between the maps, so regions retaining stronger agreement support more reliable structural detail. Regions with weaker agreement indicate reduced local interpretability. This distinction helps separate trustworthy features from apparent density that may not be reproducible.

Dividing particle images into spatial or signal-based regions makes the analysis sensitive to regional differences that a single specimen-wide value would conceal. Each region can retain or lose signal independently, allowing the resulting map to show why one domain appears sharp while another is poorly detailed. This regional view is particularly useful for heterogeneous reconstructions.

Flexible, disordered, or heterogeneous areas commonly show lower local resolution because their signal is less consistently represented in the reconstruction. That lower value does not necessarily mean the entire structure is poor; it identifies a specific region where assigning detailed features requires caution. Rigid domains may remain better resolved within the same map, supporting selective interpretation.

Unlike a global resolution value, local resolution preserves spatial variation across the reconstruction. A global number can summarize overall performance, but it cannot indicate whether limitations are concentrated in a mobile region or distributed throughout the specimen. Local analysis therefore provides a more targeted basis for judging which structural observations are reliable and which require restrained interpretation.

An analysis begins by separating particle images according to spatial or signal-based regions, then generating independent reconstructions for comparison. Fourier-based correlations are calculated between the corresponding maps, and the regional results are used to produce a local-resolution map. Researchers can then inspect variations across domains and relate them to the reconstruction's structural detail.

In biochemistry, local-resolution maps help guide model building and the interpretation of protein-ligand interactions. They also support assessment of conformational variability and decisions about which features can be assigned confidently. For a protein reconstruction, the map can connect regional signal quality with biochemical questions while warning investigators against treating poorly resolved density as equally informative everywhere.