Sample concentration technology In immunoenzyme technology, sometimes it is necessary to concentrate the sample solution (such as antigen, antibody, enzyme, enzyme-labeled antibody or enzyme-labeled antigen). Commonly used concentration techniques are as follows: 1. Reverse dialysis method If a polymer or sucrose with a high concentration and water absorption function is placed around the dialysis bag containing the sample solution, the osmotic pressure inside the membrane is lower than that outside The protein in the sample solution is concentrated. Commonly used polymers are Polyvinylpyrrolidone (Polyvinylpyrrolidone, referred to as PVP, molecular weight about 12000), polyethylene glycol (Polyethylene glycol, referred to as PEG, also known as Carbowax, molecular weight about 6000, but the molecular weight of PEG is available in 5000-10000 ), The water absorbing agent does not have to use a dry agent, a 30% concentrated solution can be used to absorb water faster. Alkaline solution is often added to concentrated PEG solution to neutralize acidity. The water-absorbing agent can be recovered by heating or blowing after use. The concentration effect of PVP and PEG is good, but small molecular weight polymers easily enter the membrane, and PVP can absorb ultraviolet light at 280nm wavelength. Because sucrose easily enters the membrane, it is required that sucrose must be of high purity and has no effect on the next step (such as immunizing animals). The advantage of sucrose is that it is convenient to source, but it will affect the concentration effect due to the small molecular weight. 2. Gel water absorption method gels such as dextran gel and polyacrylamide gel are polymer particles with micropores with a certain pore size and water absorption properties. Add gel particles with a smaller pore size to the protein sample solution. Can absorb moisture in the sample to achieve the purpose of concentration. Generally, Sephadex G25 or G50 is used, and the concentration effect is good, and the adsorption is also small. The protein concentrate can be obtained by centrifuging the water-absorbing gel. 3. Evaporation and dehydration method The sample liquid is packed in the dialysis bag, hung up, and evaporated at a low temperature with a fan, or the sample liquid is poured into a flat enamel shallow basin, and the fan is blown to evaporate, which can achieve the purpose of concentration. This method is simple, but it takes a long time and will increase the salt concentration in the sample. Therefore, the volatile buffer solution should be dialyzed before or during concentration, and then concentrated by evaporation to water. 4. Freezing method When the sample liquid is frozen, water molecules form ice, and salts and protein molecules do not enter the ice but remain in the liquid phase. During operation, the sample liquid is first cooled to a solid state, and then slowly melted, and the purpose of removing most of the solvent is achieved by using the difference between the melting point of the solvent and the solute. For example, in the concentration of enzymes, pure ice crystals that do not contain enzymes are floated on the liquid surface by freezing, the enzymes are concentrated in the lower layer solution, and the upper layer of ice is removed to obtain the concentrated solution of the enzyme. 5.Ultrafiltration concentration method When concentrating samples, the ultrafiltration method is also very important. It can concentrate 500ml of very dilute sample solution more than 300 times in 3-4h without denaturing the protein, and the recovery rate is as high as 90 %the above. The ultrafiltration concentration method is a method for selectively filtering various solute molecules in the sample liquid by means of a special membrane. When the sample liquid passes through a special membrane at a certain pressure, solvents and small molecules pass through, and large molecules are retained in the original sample liquid due to the retention of the membrane. This is an emerging technology for concentration, desalting, and separation and purification of biological macromolecules. . Nail Files,Sponge Nail File,Multi-Function Nail File,Manicure Nail File Yangjiang Etina Houseware Co., Ltd. , https://www.etinanailtools.com
Sample concentration technology