Direct calculation of variable-resolution maps by fully analytic approximations to atomic images.

Area of Science:

• Structural biology
• Biophysical chemistry

Background:

• Crystallographic maps traditionally use Fourier series with uniform resolution.
• Cryo-electron microscopy (cryo-EM) maps exhibit variable local resolution, complicating comparisons.
• Standard methods for generating model maps are inadequate for variable local resolution data.

Purpose of the Study:

• To develop a computational method for generating model maps that accurately reflect local resolution variations in cryo-EM data.
• To enable more reliable comparisons between experimental cryo-EM maps and corresponding atomic models.

Main Methods:

• Proposed a stand-alone program for calculating model maps.
• Represented model maps as sums of atomic images using the shell-function approximation.
• Developed analytic functions for atomic images dependent on atomic displacement parameters and local resolution.

Main Results:

• The proposed method generates model maps using atomic images as analytic functions.
• This approach explicitly incorporates local resolution information for each atom.
• The method simplifies the calculation of model maps for cryo-EM data with heterogeneous resolution.

Conclusions:

• The developed program provides an effective strategy for computing model maps with variable local resolution.
• This facilitates accurate structural model refinement and validation in cryo-EM.
• The analytic representation of atomic images improves computational efficiency and accuracy.