Search results
Results from the WOW.Com Content Network
Series of density maps for GroEL: from left to right, 4 Å, 8 Å, 16 Å, and 32 Å resolution.The details are smeared away as the resolution becomes lower. Resolution in the context of structural biology is the ability to distinguish the presence or absence of atoms or groups of atoms in a biomolecular structure.
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.
An X-ray diffraction pattern of a crystallized enzyme. The pattern of spots (reflections) and the relative strength of each spot (intensities) can be used to determine the structure of the enzyme. The relative intensities of the reflections provides information to determine the arrangement of molecules within the crystal in atomic detail.
Cesium chloride is a simple cubic crystal lattice with a basis of Cs at (0,0,0) and Cl at (1/2, 1/2, 1/2) (or the other way around, it makes no difference). Equation ( 8 ) becomes
Grazing incidence atom scattering, [9] [10] where the fact that atoms (and ions) can also be waves is used to diffract from surfaces. Quantum reflection, where very low kinetic energy atoms or molecules are diffracted (reflected) from surfaces. [11]
Typically, powder X-ray diffraction (XRD) is an average of randomly oriented microcrystals that should equally represent all crystal orientation if a large enough sample is present. X-rays are directed at the sample while slowly rotated that produce a diffraction pattern that shows intensity of x-rays collected at different angles. Randomly ...
The possible screw axes are: 2 1, 3 1, 3 2, 4 1, 4 2, 4 3, 6 1, 6 2, 6 3, 6 4, and 6 5. Wherever there is both a rotation or screw axis n and a mirror or glide plane m along the same crystallographic direction, they are represented as a fraction n m {\textstyle {\frac {n}{m}}} or n/m .
This is because X-rays have a refractive index n ≈ 1. Bragg came up with the equation that describes X-ray/neutron diffraction when those particles pass a crystal lattice.(X-ray diffraction) For this purpose, "perfect crystals" have been produced in many shapes, depending on the geometry and energy range of the instrument.