Resolution: Difference between revisions
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==Quick Guide== | ==Quick Guide== | ||
Here is a quick guide for interpreting values of resolution (taken from [[FirstGlance in Jmol]]). | Here is a quick guide for interpreting values of resolution (taken from [[FirstGlance in Jmol]]). | ||
* | *< ~1.7 Å: Most atoms very clearly seen. | ||
*~1.7 - 2.2 Å: Many atoms clearly seen. | *~1.7 - 2.2 Å: Many atoms clearly seen. | ||
*~2.2 - 2.8 Å: Shapes of larger sidechains seen. | *~2.2 - 2.8 Å: Shapes of larger sidechains seen. | ||
*~2.8 - 3.5 Å: Secondary structure & bulky groups seen. Atoms unclear. | *~2.8 - 3.5 Å: Secondary structure & bulky groups seen. Atoms unclear. | ||
*~3.5 - 4.0 Å: Most [[chains]] traceable | *~3.5 - 4.0 Å: Most [[chains]] traceable. Atoms unclear. | ||
*~4.0 - 6.0 Å: Some chains traceable. Atoms unclear. | *~4.0 - 6.0 Å: Some chains traceable. Atoms unclear. | ||
*~6.0 - 8.0 Å: Shapes of [[domains]] at best. Atoms unclear. | *~6.0 - 8.0 Å: Shapes of [[domains]] at best. Atoms unclear. | ||
*> 8.0 Å: Largest features seen roughly. Atoms unclear. | *> ~8.0 Å: Largest features seen roughly. Atoms unclear. | ||
Bear in mind that the resolution value represents the "best" (most ordered) parts of a crystal, and that other parts may have poorer quality. The [[temperature value]] for each atom in a crystallographic model indicates the clarity of its electron density map. | Bear in mind that the resolution value represents the "best" (most ordered) parts of a crystal, and that other parts may have poorer quality. The [[temperature value]] for each atom in a crystallographic model indicates the clarity of its electron density map. | ||
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==Electron Density Map vs. Resolution== | ==Electron Density Map vs. Resolution== | ||
The '''images at right (top of this page)''' show how the electron density map<ref name="edm">Electron density maps are the results of [[X-ray crystallography]] experiments.</ref><ref name="stills">These are "perfect" electron density maps calculated from the atomic model (R factor = 0.0%, perfect phases and amplitudes, contoured at 1 sigma). Electron density maps based on experimental data would fit the true conformation less well. Because these electron density maps were calculated from an atomic model that lacked hydrogen atoms, the [[Hydrogen in macromolecular models|electron densities for hydrogen atoms]] that would appear with experimental data at a resolution of 0.5 Å do not appear.</ref> becomes more accurate and detailed as the resolution value decreases from 5.0 Å to 0.5 Å. | The '''images at right (top of this page)''' show how the [[electron density map]]<ref name="edm">Electron density maps are the results of [[X-ray crystallography]] experiments.</ref><ref name="stills">These are "perfect" electron density maps calculated from the atomic model (R factor = 0.0%, perfect phases and amplitudes, contoured at 1 sigma). Electron density maps based on experimental data would fit the true conformation less well. Because these electron density maps were calculated from an atomic model that lacked hydrogen atoms, the [[Hydrogen in macromolecular models|electron densities for hydrogen atoms]] that would appear with experimental data at a resolution of 0.5 Å do not appear.</ref> becomes more accurate and detailed as the resolution value decreases from 5.0 Å to 0.5 Å. | ||
The images at right were taken from a movie<ref name='movie'>The movie ([[Image:Resolution_holton.mpeg]]) was created by James Holton at the Advanced Light Source of the Berkeley Laboratory at the University of California. Holton kindly gave explicit permission to use this movie in Proteopedia. The original source was http://ucxray.berkeley.edu/~jamesh/movies.</ref> in which the atomic model and electron density map rock back and forth while the resolution value (uncertainty) increases from 0.5 to 5.0 Å. | The images at right were taken from a movie<ref name='movie'>The movie ([[Image:Resolution_holton.mpeg]]) was created by James Holton at the Advanced Light Source of the Berkeley Laboratory at the University of California. Holton kindly gave explicit permission to use this movie in Proteopedia. The original source was http://ucxray.berkeley.edu/~jamesh/movies.</ref> in which the atomic model and electron density map rock back and forth while the resolution value (uncertainty) increases from 0.5 to 5.0 Å. | ||
