Talk:Resolution: Difference between revisions
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Proposed revision for the | Proposed revision for the beginning of this article, after discussion with Keiichi Namba. Comments welcome! | ||
The resolution of a macromolecular crystal is the smallest distance between crystal lattice planes that is resolved in the diffraction pattern. Thus high numeric values of resolution, such as 4 Å, mean poor resolution, while low numeric values, such as 1.5 Å, mean good resolution. '''2.05 Å''' is the '''median''' resolution for [[X-ray crystallography|X-ray crystallographic]] results in the Protein Data Bank (88,701 on May 15, 2014). | The resolution of a macromolecular crystal is the smallest distance between crystal lattice planes that is resolved in the diffraction pattern. Thus high numeric values of resolution, such as 4 Å, mean poor resolution, while low numeric values, such as 1.5 Å, mean good resolution. '''2.05 Å''' is the '''median''' resolution for [[X-ray crystallography|X-ray crystallographic]] results in the Protein Data Bank (88,701 on May 15, 2014). | ||
After an [[electron density map]] is calculated and refined with a fitted atomic model, an uncertainty of atomic position is calculated for each atom in the model. These single-atom uncertainties are called the B factors or temperature values of the atoms (see [[Temperature]]). | |||
==Determination of Resolution== | |||
The portion of the macromolecule that is best ordered in the crystal is responsible for diffraction spots that are farthest from the axis of the X-ray beam. Resolution is determined from these farthest spots based on their angle θ from the X-ray beam, using [http://en.wikipedia.org/wiki/Bragg's_law the Bragg equation] solved for ''d'': | The portion of the macromolecule that is best ordered in the crystal is responsible for diffraction spots that are farthest from the axis of the X-ray beam. Resolution is determined from these farthest spots based on their angle θ from the X-ray beam, using [http://en.wikipedia.org/wiki/Bragg's_law the Bragg equation] solved for ''d'': | ||
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If some portions of the macromolecule are less ordered in the crystal than others, these will have a poorer resolution. The "resolution of the crystal" represents the most ordered portions. | If some portions of the macromolecule are less ordered in the crystal than others, these will have a poorer resolution. The "resolution of the crystal" represents the most ordered portions. | ||
