X-ray crystallography: Difference between revisions
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About 88% of the models (entries) in the [[Protein Data Bank|World Wide Protein Data Bank]] were determined by X-ray crystallography (August, 2021). (About 7% were determined by [[NMR|solution nuclear magnetic resonance]], and about 5% by [[cryo-EM]].) Analysis of x-ray diffraction patterns from protein crystals produces an [[Electron density maps|electron density map]], into which an atomic model of the protein is fitted. Major errors sometimes occur when fitting models in to low-[[Resolution|resolution]] electron density maps (see [[Quality assessment for molecular models]]). The value of [[Free R]] is the best clue as to whether major errors may be present in a published model. | About 88% of the models (entries) in the [[Protein Data Bank|World Wide Protein Data Bank]] were determined by X-ray crystallography (August, 2021). (About 7% were determined by [[NMR|solution nuclear magnetic resonance]], and about 5% by [[cryo-EM]].) Analysis of x-ray diffraction patterns from protein crystals produces an [[Electron density maps|electron density map]], into which an atomic model of the protein is fitted. Major errors sometimes occur when fitting models in to low-[[Resolution|resolution]] electron density maps (see [[Quality assessment for molecular models]]). The value of [[Free R]] is the best clue as to whether major errors may be present in a published model. | ||
Obtaining diffraction-quality crystals of proteins can be very difficult for some proteins, despite many recent advances<ref name="intro">PMID: 24419610</ref>. For every new protein sequence targeted for X-ray crystallography, about one in twenty is solved<ref>[ | Obtaining diffraction-quality crystals of proteins can be very difficult for some proteins, despite many recent advances<ref name="intro">PMID: 24419610</ref>. For every new protein sequence targeted for X-ray crystallography, about one in twenty is solved<ref>[https://www.umass.edu/molvis/workshop/allstruc/xrc_succ.htm Success Rates in Protein Crystallography]</ref><ref>[https://www.umass.edu/molvis/workshop/allstruc/xsuccess.htm Structural Genomics Progress Chart]</ref>. Efforts are underway to improve this success rate<ref>PMID: 22653729</ref>. | ||
<center><table width="450"><tr><td>[[Image:Protein crystals samatey.png]]</td><td> </td><td>Crystals of the [[Flagellar hook of bacteria|flagellar hook protein]] FlgE from ''C. jejuni'' produced in the [[Fadel_A._Samatey_Group|Samatey lab]].</td></tr></table></center> | <center><table width="450"><tr><td>[[Image:Protein crystals samatey.png]]</td><td> </td><td>Crystals of the [[Flagellar hook of bacteria|flagellar hook protein]] FlgE from ''C. jejuni'' produced in the [[Fadel_A._Samatey_Group|Samatey lab]].</td></tr></table></center> | ||