What is isomorphous structure?
In crystallography crystals are described as isomorphous if they are closely similar in shape. These requirements ensure that the forces within and between molecules and ions are approximately similar and result in crystals that have the same internal structure.
What are isomorphous crystals?
Two crystals are said to be isomorphous if (a) both have the same space group and unit-cell dimensions and (b) the types and the positions of atoms in both are the same except for a replacement of one or more atoms in one structure with different types of atoms in the other (isomorphous replacement), such as heavy …
Why is tungsten used in crystallographic phasing experiments?
The Use of Tungsten Atoms to Solve the Phase Problem. POTs are excellent phasing tools as they represent clusters of numerous anomalously scattering heavy atoms that provide signals that significantly differ from those of the native data set enabling phase determination.
What are phases in crystallography?
In physics, the phase problem is the problem of loss of information concerning the phase that can occur when making a physical measurement. The name comes from the field of X-ray crystallography, where the phase problem has to be solved for the determination of a structure from diffraction data.
What is molecular replacement in crystallography?
Molecular replacement (or MR) is a method of solving the phase problem in X-ray crystallography. MR relies upon the existence of a previously solved protein structure which is similar to our unknown structure from which the diffraction data is derived.
What is isomorphous example?
Sodium nitrate and calcium sulfate are good examples of isomorphous substances. Because both have similar structure and shape. The isomorphous substances are also called double salt. All the double salts are not isomorphous substances.
Which of the following pairs is not isomorphous?
NaCl and KCl pair of compounds is NOT isomorphous.
How do you identify an isomorphous compound?
isomorphous substances should have similar chemical formulae. In isomorphous compounds, the ratio between masses of two elements which combine with the same combined mass of all other elements is the same as the ratio between their atomic masses.
What are isomorphous crystals give example?
These two crystals are known as isomorphous substances. Sodium nitrate and calcium sulfate are good examples of isomorphous substances. Because both have similar structure and shape. The isomorphous substances are also called double salt.
What is the purpose of molecular replacement?
The term ‘molecular replacement’ (MR) is generally used to describe the use of a known molecular model to solve the unknown crystal structure of a related molecule.
How does isomorphous replacement solve the phase problem?
The classical method for solving the phase problem in macromolecular crystal structures, known as isomorphous replacement, dates back to the earliest days of protein crystallography.10,16 The concept is simple enough: we introduce into the protein crystal an atom or atoms heavy enough to affect the diffraction pattern measurably.
Can a Single Isomorphous derivative be used for structure determination?
A good single isomorphous derivative may be sufficient for structure determination (single isomorphous replacement, SIR), but usually multiple derivatives are necessary to derive phase information (multiple isomorphous replacement, MIR).
How are cryo-EM maps used in crystallography?
Cryo-EM maps can be used to initiate crystallographic phasing. Isomorphous replacement phasing methods that are routinely used in X-ray crystallography are technically difficult to apply to large macromolecular complexes. A low-resolution cryo-EM map of the complex under study thus provides a valuable complementary source of phase information.
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