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In general, small molecules are also easier to crystallize than macromolecules; however, X-ray crystallography has proven possible even for viruses and proteins with hundreds of thousands of atoms, through improved crystallographic imaging and technology. [96] The technique of single-crystal X-ray crystallography has three basic steps.
In X-ray crystallography, resolution is a measure of the resolvability or precision in the electron density map of a molecule. Resolution is usually reported in Angstroms (Å, 10 –10 meters) for X-ray crystal structures. The smaller the number, the better the degree of atomic resolution.
The first of these is by X-ray crystallography, starting in 1958 when the crystal structure of myoglobin was determined. The second method is by NMR, which began in the 1980s when Kurt Wüthrich outlined the framework for NMR structure determination of proteins and solved the structure of small globular proteins. [5]
[3] [4] Contrary to X-ray, single crystals are not necessary with solid-state NMR and structural information can be obtained from high-resolution spectra of disordered solids. [5] E.g. polymorphism is an area of interest for NMR crystallography since this is encountered occasionally (and may often be previously undiscovered) in organic ...
Nucleic acid NMR is the use of NMR spectroscopy to obtain information about the structure and dynamics of nucleic acid molecules, such as DNA or RNA. As of 2003, nearly half of all known RNA structures had been determined by NMR spectroscopy. [2] Nucleic acid NMR uses similar techniques as protein NMR, but has several differences.
The most prominent techniques are X-ray crystallography, nuclear magnetic resonance, and electron microscopy. Through the discovery of X-rays and its applications to protein crystals, structural biology was revolutionized, as now scientists could obtain the three-dimensional structures of biological molecules in atomic detail. [2]
XANES – XANES, synonymous with NEXAFS (near edge X-ray absorption fine structure) XAS – X-ray absorption spectroscopy; X-CTR – X-ray crystal truncation rod scattering; X-ray crystallography; XDS – X-ray diffuse scattering; XES – X-ray emission spectroscopy; XPEEM – X-ray photoelectron emission microscopy; XPS – X-ray photoelectron ...
A set of conformations, determined by NMR or X-ray crystallography may be a better representation of the experimental data of a protein than a unique conformation. [23] The utility of a model will be given, at least in part, by the degree of accuracy and precision of the model.