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    Home > Biochemistry News > Biotechnology News > The precipitation reaction of proteins.

    The precipitation reaction of proteins.

    • Last Update: 2020-10-26
    • Source: Internet
    • Author: User
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    , Purpose:1. To deepen
    understanding
    collosal solution stabilizing factors in proteins and proteins.
    2. Learn about several ways to precipitate proteins and their practical significance.
    3. Understand the relationship between protein denaturation and precipitation.
    II, principle:
    protein molecules in aqueous solutions become stable hydro-hydrocolletic particles due to the surface generation of hydration and double electron layers, under the influence of certain physical and chemical factors, protein particles can be precipitated due to loss of charge and dehydration.
    of proteins can be divided into two categories.
    (1) Reversible precipitation reaction At this time the structure of protein molecules has not changed significantly, after removing the factors that cause precipitation, protein precipitation can still dissolve in the original solvent, and maintain its natural properties and non-variability. For example, most proteins act on saline or use ethanol (or acetone) for a short period of time at low temperatures. Such reactions are often used when purification proteins.
    (2) irreversible precipitation reaction At this time, the internal structure of protein molecules has under changed significantly, the protein is normally degenerated and precipitated, no longer dissolved in the original solvent.
    precipitation
    solidification caused by heating, proteins react with heavy metal ions or
    some
    organic acids.
    protein denaturation, sometimes due to the conditions that maintain the stability of the solution still exist (e.g. charge), do not be out. Therefore, denatured proteins do not necessarily manifest as precipitation, and precipitated proteins are not necessarily denatured.
    , operation steps:
    1. The strong solution of the protein's saline inorderable salts (ammonium sulfate, sodium sulfate, sodium chloride, etc.) can dissect the protein. The concentration of salt is different, and the proteins produced are different.
    such as globulin can be in the semi-saturated ammonium sulfate solution, while the clear protein in the saturated ammonium sulfate solution can be in the analysis.
    the protein precipitation obtained by salt analysis, when reducing its salt concentration, it can be dissolved again, so the salt analysis of protein is a reversible process.
    plus 5% egg white protein solution 5 ml in
    tit tube
    , plus the same amount of saturated ammonium sulfate solution, after mixing and resting for a few minutes to precipitate the globulin precipitation. Pour out a small amount of turbid precipitation, add a small amount of water, observe whether it dissolves, why? The contents of the tube
    filter
    , add ammonium sulfate powder to the filter until it no longer dissolves, at which point the precipitated precipitation is clear protein.
    part of the clear protein, add a small amount of distilled water, observe the precipitation of the resoluble.
    2. Heavy metal ion precipitation protein Heavy metal ions bind to protein into a water-insoluble complex.
    1 test tube, add 2 ml of protein solution, and add 3% silver nitrate solution 1 to 2 drops, oscillating test tube, precipitation produced. Place for a moment, pour over the liquid, add a small amount of water to the precipitation, is the precipitation dissolved? Why?
    3. Some organic acid precipitation proteins take 1 test tube, add 2 ml of protein solution, add 1 ml of tricloste solution, oscillate test tube, observe the precipitation generation. Place for a moment, pour out the liquid, add a small amount of water to the precipitation, and observe if the precipitation dissolves.
    4. Organic solvent precipitation protein Take 1 test tube, add 2 ml protein solution, and add 2 ml 95% ethanol. Mix well and observe the generation of precipitation.
    5. Ethanol-induced denaturation and precipitation Take 3 test tubes, numbered. Add the reagents
    the following
    :after shaking and mixing, observe any changes in the tubes. Place for a moment, add 8 ml of water to each tube, then add a drop of methyl red in tubes 2 and 3, and use 0.1 mol. L-1 acetic acid solution and 0.05 mol. L-1 Sodium carbonate solution. Observe the change of color of each tube and the generation of precipitation. Add 0.1 mol per tube. L-1 hydrochloric acid solution number of drops, observe the re-dissolution of precipitation. Explain all the phenomena that occur in each tube.
    .
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