Resolution (structural biology)

The resolution is measured of the "map" of the structure produced from experiment, where an atomic model would then be fit into.

[2] In structural biology, resolution can be broken down into 4 groups: (1) sub-atomic, when information about the electron density is obtained and quantum effects can be studied, (2) atomic, individual atoms are visible and an accurate three-dimensional model can be constructed, (3) helical, secondary structure, such as alpha helices and beta sheets; RNA helices (in ribosomes), (4) domain, no secondary structure is resolvable.

By contrast, macromolecular crystallography often involves tens of thousands of atoms in the unit cell.

In general, small molecules are also easier to crystallize than macromolecules; however, X-ray crystallography has proven possible even for viruses with hundreds of thousands of atoms.

However, fixed-value thresholds (like 0.5, or 0.143) were argued to be based on incorrect statistical assumptions,[12] though 0.143 has been shown to be strict enough so as to likely not overestimate resolution.