12 - X-ray crystallography III: NMR, cryo-EM

what is an electron density map?

3D map of electrons that are present within a unit cell

what is a B factor?

measure of disorder

what are rotamers and when does it occur?

side chains have 2 possible conformations so both are shown in the electron density map

* occur at high resolutions

what is the R factor?

the accuracy of the fit of the model to the data

what value of R is considered good?

less than 0.25

how does NMR function?

by observing magnetic moments cause the nuclei to spin

whats a downside of NMR?

need lots of soluble protein

how do you interpret NMR results

chemical shifts correspond to a nuclei in the molecule and the chemical shift tells about the environment

* the structure can then be determined

what is cyro-EM?

beam of electrons fired at frozen proteins, the scatter of light is caught on electron detector and derived