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Protein crystallization is the process of formation of a regular array of individual protein molecules stabilized by crystal contacts. If the crystal is sufficiently ordered, it will diffract . Some proteins naturally form crystalline arrays, like aquaporin in the lens of the eye.
Crystallization separates a product from a liquid feed stream, often in extremely pure form, by cooling the feed stream or adding precipitants that lower the solubility of the desired product so that it forms crystals. The pure solid crystals are then separated from the remaining liquor by filtration or centrifugation.
For protein crystals this method is conducted by soaking the crystal of a sample to be analyzed with a heavy atom solution or co-crystallization with the heavy atom. The addition of the heavy atom (or ion) to the structure should not affect the crystal formation or unit cell dimensions in comparison to its native form, hence, they should be ...
Since biomolecular condensation generally involves oligomeric or polymeric interactions between an indefinite number of components, it is generally considered distinct from formation of smaller stoichiometric protein complexes with defined numbers of subunits, such as viral capsids or the proteasome – although both are examples of spontaneous ...
For example, proteins and larger RNA molecules cannot be crystallized if their tertiary structure has been unfolded; therefore, the range of crystallization conditions is restricted to solution conditions in which such molecules remain folded. [citation needed] Three methods of preparing crystals, A: Hanging drop. B: Sitting drop. C: Microdialysis
The source of the protein can be either natural or produced in a production system using recombinant DNA techniques through genetic engineering. Recombinantly expressed proteins are usually easier to produce in sufficient quantity, and this method makes isotopic labeling possible. [citation needed]
Lipid cubic phases, spontaneous self-assembling liquid crystals or lipid mesophases have been used successfully in the crystallization of integral membrane proteins. [6] Temperature, salts, detergents, various additives are used in this system to tailor the cubic phase to suit the target protein.
MicroED, [28] method to determine the structure of proteins, peptides, organic molecules, and inorganic compounds using electron diffraction from 3D crystals [29] [30] [31] Single particle analysis cryo-EM, an averaging method to determine protein structure from monodisperse samples. [32]