After the antigen specifically binds to the antibody, although it changes from a hydrophilic colloid to a hydrophobic colloid, if no electrolyte is present in the solution, no visible reaction occurs. In order to promote the formation of precipitates or aggregates, 0.85% sodium chloride or various buffers are commonly used as diluents for antigens and antibodies. Since sodium chloride dissociates into Na+ and C1- in an aqueous solution, the charge on the colloidal particles can be neutralized, respectively, and the potential of the colloidal particles is lowered. When the potential drops below the critical potential (12-15 mV), the antigen-antibody complex is allowed to precipitate out of solution, forming a visible precipitate or agglomerate.
(a) pH
The antigen-antibody reaction must be carried out in a suitable pH environment. Proteins have amphoteric ionization properties, so each protein has a fixed isoelectric point. The antigen-antibody reaction is generally carried out at a pH of 6-8. If the pH is too high or too low, the physicochemical properties of the antigen and the antibody will be affected. For example, when the pH reaches or approaches the isoelectric point of the antigen, even if no corresponding antibody is present, non-specific aggregation of the particulate antigen is caused, resulting in a false positive reaction.
(2) Temperature
Within a certain range, the temperature rise can accelerate the molecular motion, and the chance of collision between the antigen and the antibody increases, and the reaction is accelerated. However, if the temperature is higher than 56 ° C, the bound antigen antibody may be dissociated or even denatured or destroyed; at 40 ° C, the binding speed is slow, but the binding is firm and easier to observe. The commonly used antigen-antibody reaction temperature is 37 °C. Each test has its own unique optimal reaction temperature. For example, the cold agglutinin is best combined with red blood cells at around 4, and dissociated at 20 °C or higher. In addition, proper shaking can also promote contact of antigen-antibody molecules and accelerate the reaction.
High Content Monomer
Plant extraction process
1. Select plants/medicinal materials. It is nothing more than ancient prescriptions, proven prescriptions, and folk medicinal herbs. At present, common and uncommon medicinal materials have been studied. Most of the time, the amount of medicinal materials has been increased to extract low-isolated components, or medicinal plants have not been studied from Miao medicine, Tibetan medicine, Mongolian medicine, Africa, Latin America and other places.
2. Extract. Solvent petroleum ether, n-hexane, cyclohexane, benzene, chloroform, ethyl acetate, n-butanol, acetone, ethanol, methanol, water (small polarity → large polarity). Daily decoction of medicines is effective, use water and ethanol and other solvents with high polarity. Artemisinin and other boiling methods are not effective, use petroleum ether and other solvents with low polarity. The common medicinal materials, water/alcohol/ether, are presented again, and more compounds can be separated and identified.
3. Separation. This is the most important task. There are dozens of compounds in the solution extracted in the second step. Generally, column chromatography is used, which is what we often call column flushing. The workload is large, boring, and low-tech. A master's degree may do this every day for 2 years of experimentation. As shown in the figure below, the column for separating compounds is as large as 2 meters high and as small as 10 cm. Change the solvent conditions of the mobile phase, change the material of the column, and repeatedly wash the column under different conditions and separation principles to separate the monomer compound.
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