Asymmetric Unit: Difference between revisions
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The asymmetric unit (see definition in the next paragraph) is what is contained in the protein model that crystallographers publish in the [[Protein Data Bank]]. It is not to be confused with the biologically functional unit ([[Biological Unit]]), which may be the same, smaller, or larger than the asymmetric unit. | The asymmetric unit (see definition in the next paragraph) is what is contained in the protein model that crystallographers publish in the [[Protein Data Bank]]. It is not to be confused with the biologically functional unit ([[Biological Unit]]), which may be the same, smaller, or larger than the asymmetric unit. | ||
<applet load='2qcb' size='350' frame='true' align='right' caption='Streptavidin (2qcb)' /> | |||
The '''asymmetric unit''' is the smallest portion of a crystal that, when duplicated and moved by crystal symmetry operations, can produce the unit cell of the crystal. The symmetry operations that are common for biological molecules are rotation, translation, and screw operations (which combine rotation and translation). Mirror symmetry planes occur rarely in crystals of biological molecules due to the presence of chiral centers, e.g. L or D amino acids. | The '''asymmetric unit''' is the smallest portion of a crystal that, when duplicated and moved by crystal symmetry operations, can produce the unit cell of the crystal. The symmetry operations that are common for biological molecules are rotation, translation, and screw operations (which combine rotation and translation). Mirror symmetry planes occur rarely in crystals of biological molecules due to the presence of chiral centers, e.g. L or D amino acids. | ||
