It is also called detergent. Its main component is surfactant (in some cases, it refers to surfactant, which can be divided into anion, cation, neutral detergent and other types. Neutral detergent is widely used in protein extraction). It may also includeAbrasive, pH regulator,acid，Hard water softener，Oxidant，enzyme，foaming agent，Whitening agent, diluent, etc.
Chromic acid cleaning solution: It is prepared by potassium dichromate and concentrated sulfuric acid, and is oxidizing and acidic. It is used to clean stains on chemical instruments
Surfactant: usually composed of a polar head and a non-polar tail, used to remove stains that are difficult to dissolve in water
Bleaching agent: it usually contains hypochlorite, which is oxidized
Dilute hydrochloric acid: used to remove alkaline stains, such as lumps in the toilet
Sodium carbonate solution: used to remove oil stains. Its principle is that ester is hydrolyzed in alkaline solution. See saponification reaction
Type of detergent (surfactant)
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A. Neutral detergent, also known as non-ionic surfactant, has less influence on protein denaturation and is suitable for protein or enzyme extraction.Generally, neutral detergents on the market include polyethylene glycol, such as PEG200;Polyol surfactants, such assorbitol, driver type and Tween type;Polyoxyethylene fatty alcohol ethers, such as Benzene and Pinnacle;Polyoxyethylene alkylphenol ether, such as Igepal CO, emulsifier OP, Triton, Pluronic (used as defoamer, wetting agent, and solvent), and foam enemy.After the action of neutral detergent, it can be removed through Sephadex LH-50 column;The target protein can also be separated directly on DEAE Sephadex column chromatography without removing the detergent first.
B. The common anionic detergents are sodium dodecyl sulfate and sodium dodecyl sulfonate.The former can promote the dissolution of nucleoprotein, release nucleic acid, and inhibit nuclease to a certain extent. It is often used for the extraction of nucleic acid.
C. Cationic detergents such as benzalkonium bromide, benzalkonium bromideCTAB、CPC、ZEPH、Clostridium bromide, TMPB, DUMIFEN, etc., most of them are disinfection and sterilization.
D. Natural surfactants, also known as biosurfactants, include a wide range of types, such as various gums (gum arabic, apricot gum, peach gum, pectin), gelatin, saponins, lecithin, soybean phospholipid, agar, sodium alginate, casein, cholesterol, cholic acid, polysaccharides (such as cyclodextrin), etc.
E. The amphoteric surfactant is an anionic surfactant in alkaline aqueous solution, with good foaming property and strong detergency;In acid solution, it shows the characteristics of cationic surfactant, and its bactericidal property is very strong.
Application of GPA in protein extraction
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The role of protein denaturants is to destroy the secondary bonds of proteins, such as hydrogen bonds, salt bonds and hydrophobic force, causing the disintegration of natural conformation;They do not destroy covalent bonds, such as peptide bonds and disulfide bonds, so they do not involve changes in the primary structure.There are two types of denaturants: dissolved and precipitated. SDS, urea and guanidine salt are effective dissolved denaturants, while trichloroacetic acid, methanol, and chloroform/isopentyl alcohol are effective precipitated denaturants.In general, denaturants are often used in large quantities. The amount of denaturants that destroy hydrogen bonds is at least twice the molar number of amino acids. For example, 1 gram of protein is combined with 1.4 grams of cocoa.SDS can be dissolved in water up to 25%, which is sensitive to temperature. W/V storage solution is the most convenient.It should be noted that the potassium salt of SDS is insoluble, so the potassium salt should not be mixed into the SDS solution.Urea is very soluble in water, up to 10mol/L, and temperature shall be noted above 8mol/L to prevent precipitation.Urea decomposes slowly in water to form ammonia and highly active cyanate ion, so high temperature shall be prevented.Trichloroacetic acid and perchloric acid (TCA, PCA) are excellent precipitants, which can precipitate protein and nucleic acid. The former is more widely used.
It is a very useful technique to grow protein crystals with detergent as an additive.Non ionic and zwitterionic crystallizing agents have been well used in membrane protein crystallization, and have now become conventional experimental means.Detergents also play a role in some soluble proteins, improving the quality of crystals and the repeatability of results, and promoting the growth of single crystals, but the specific mechanism is still unclear.The possible reason is that the introduction of detergent makes the protein molecules in the crystal droplets more hydrophilic and increases the number of homogeneous protein molecules in the solution.[1]
