# Background Electron density maps are the direct results of X-ray crystallography, and the atomic model is the interpretation of the map. So if we want to check the uncertainties of one published model, it's a must to examine the correspondence bwtween its density map and itself. # Methods For me, density of one crystal structure can be accessed through two ways. One is to check it online, using [PDB](https://www.rcsb.org), and the others is to use software `coot`. ## Online Tool 1. Go to the `Summary page` of one pdb, such as [https://www.rcsb.org/structure/3ehv](https://www.rcsb.org/structure/3ehv) 2. Go to the subpage `3D View`, such as [https://www.rcsb.org/3d-view/3EHV](https://www.rcsb.org/3d-view/3EHV) 3. In the right part, you can find a button `Density`. Click it, then the button `Enable` 4. Click one residue, and the density map will show. ## Local software # Notes # References [Basic information](https://proteopedia.org/wiki/index.php/Electron_density_maps) [File format](https://www.rcsb.org/docs/general-help/x-ray-electron-density-maps)