Editing Crystallography (section)

=== Biology ===
[[X-ray crystallography]] is the primary method for determining the molecular conformations of biological [[macromolecule]]s, particularly [[protein]] and [[nucleic acid]]s such as [[DNA]] and [[RNA]]. The double-helical structure of DNA was deduced from crystallographic data. The first crystal structure of a macromolecule was solved in 1958, a three-dimensional model of the myoglobin molecule obtained by X-ray analysis.<ref>{{Cite journal | doi = 10.1038/181662a0| title = A Three-Dimensional Model of the Myoglobin Molecule Obtained by X-Ray Analysis| journal = Nature| volume = 181| issue = 4610| pages = 662–6| year = 1958| last1 = Kendrew | first1 = J. C.| last2 = Bodo | first2 = G.| last3 = Dintzis | first3 = H. M.| last4 = Parrish | first4 = R. G.| last5 = Wyckoff | first5 = H.| last6 = Phillips | first6 = D. C. | pmid=13517261|bibcode = 1958Natur.181..662K | s2cid = 4162786}}</ref> The [[Protein Data Bank]] (PDB) is a freely accessible repository for the structures of proteins and other biological macromolecules. Computer programs such as [[RasMol]], [[Pymol]] or [[Visual Molecular Dynamics|VMD]] can be used to visualize biological molecular structures.
[[Neutron crystallography]] is often used to help refine structures obtained by X-ray methods or to solve a specific bond; the methods are often viewed as complementary, as X-rays are sensitive to electron positions and scatter most strongly off heavy atoms, while neutrons are sensitive to nucleus positions and scatter strongly even off many light isotopes, including hydrogen and deuterium.
[[Electron diffraction]] has been used to determine some protein structures, most notably [[membrane protein]]s and [[viral capsid]]s.