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NMR has advantages over X-ray crystallography, which is the other method for high-resolution nucleic acid structure determination, in that the molecules are being observed in their natural solution state rather than in a crystal lattice that may affect the molecule's structural properties. It is also possible to investigate dynamics with NMR.
An advantage of cryo-EM over x-ray crystallography is that the samples are preserved in their aqueous solution state and not perturbed by forming a crystal of the sample. One disadvantage, is that it is difficult to resolve nucleic acid or protein structures that are smaller than ~75 kilodaltons , partly due to the difficulty of having enough ...
X-ray diffraction is a generic term for phenomena associated with changes in the direction of X-ray beams due to interactions with the electrons around atoms. It occurs due to elastic scattering, when there is no change in the energy of the waves. The resulting map of the directions of the X-rays far from the sample is called a diffraction pattern.
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.
[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 ...
A common goal of these investigations is to obtain high resolution 3-dimensional structures of the protein, similar to what can be achieved by X-ray crystallography. In contrast to X-ray crystallography, NMR spectroscopy is usually limited to proteins smaller than 35 kDa, although larger structures have been solved. NMR spectroscopy is often ...
Crystallographic methods depend mainly on analysis of the diffraction patterns of a sample targeted by a beam of some type. X-rays are most commonly used; other beams used include electrons or neutrons. Crystallographers often explicitly state the type of beam used, as in the terms X-ray diffraction, neutron diffraction and electron diffraction ...
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.