How to estimate the maintenance protein needs of animals based on factorial methods

The various methods of separating protein mixtures are mainly based on the following properties of the protein in solution: 1) molecular size; 2) solubility; 3) electric charge; 4) adsorption properties; 5) Separation of biological affinities of other molecules. Common methods for isolating and purifying proteins are:

1. Salting-out and organic solvent precipitation: adding a large amount of neutral salt to the protein solution to destroy the colloidal properties of the protein and precipitate the protein from the solution, which is called salting-out. Commonly used pre-neutral salts are:

Ammonium sulfate, sodium chloride, sodium sulfate, etc. When salting out, the pH of the solution works best at the isoelectric point of the protein. Any organic solvent that can be mixed with water in any proportion, such as ethanol, methanol, acetone, etc., can cause protein precipitation.

2. Electrophoresis: Protein molecules have a net negative or positive charge in the solution above or below their PI, so they can move in the electric field. The magnitude of electrophoretic mobility depends mainly on the amount of charge carried by the protein molecule and the size of the molecule.

3. Dialysis method: The ultrafiltration properties of the dialysis bag membrane can be used to separate macromolecular substances from small molecules. 4. Chromatography:

The separation is carried out by taking advantage of the differences in the physical and chemical properties of each component in the mixture, and the distribution between the two phases (stationary phase and mobile phase) that are in contact with each other. There are mainly ion exchange chromatography, gel chromatography, adsorption chromatography and affinity chromatography, among which gel chromatography can be used to determine the molecular weight of proteins. 5. Molecular sieve:

Also known as gel filtration method, the protein solution is added to the top of the column, let it leak down, and the small molecule protein enters the well, so it stays in the column for a long time, and the macromolecular protein can not enter the well and flow out, so the protein of different sizes can be separated. 6. Ultracentrifugation: Using the different density of substances, after ultracentrifugation, they are distributed in different liquid layers and separated.

Ultracentrifugation can also be used to determine the molecular weight of a protein, which is proportional to its sedimentation coefficient s.

1. Isoelectric point precipitation method.

Isoelectric point precipitation is a method that uses the lowest solubility of proteins at the isoelectric point and the characteristics of various proteins with different isoelectric points for separation.

At the isoelectric point, the protein molecule exists in the form of zwitterionic ions, and its molecular net charge is zero (that is, the positive and negative charges are equal), at this time, the protein molecular particles in the solution do not have the same charge to repel each other, the force between the molecules is weakened, and the particles are very easy to collide and condense and produce precipitation, so the protein has the smallest solubility at the isoelectric point, and it is most likely to form a precipitate.

Many of the physical properties at the isoelectric point, such as viscosity, expansion, osmotic pressure, etc., are reduced, which facilitates the filtration of suspensions.

2. Salting-out. Salting-out refers to the phenomenon of adding neutral salts to the aqueous solution of proteins, and precipitating the proteins with the increase of salt concentration. Neutral salt is a strong electrolyte, and the solubility is large, in the protein solution, on the one hand, it competes with the protein for water molecules and destroys the water film on the surface of the protein colloidal particles; On the other hand, a large amount of the charge on the protein particles is neutralized, so that the protein particles in the water accumulate and precipitate.

After adding some inorganic salt solutions to some protein solutions, the solubility of the protein can be reduced, so that the protein can be coagulated and precipitated from the solution, which is called salting out, which is a physical change and can be restored. Adding certain heavy metal salts to some protein solutions can change the properties of the protein and condense, and then precipitate from the solution, this effect is called denaturation, property change, is a chemical reaction, and cannot be recovered.

Animal fat or vegetable oil and sodium hydroxide are stirred and heated in a saponification pot in a certain proportion, and the high-grade fatty acid sodium, glycerol, and water formed after the reaction form a mixture (colloid). Add salt particles to the pot, stir and let stand to separate the sodium of advanced fatty acids from glycerin and water, and float on the liquid surface.

Protein precipitation is the process of precipitation of solutes in solution from the liquid phase to the solid phase. The phenomenon of protein precipitation from solution is called protein precipitation.

Commonly used methods for protein precipitation include salting out, isoelectric point precipitation, organic solvent precipitation, alkaloid reagent and certain acids (such as trichloroacetic acid) precipitation.

The principle of the Bradford method to determine the protein content is that Coomassie Brilliant Blue G250 can be color-developed by combining with protein, reading at absorbance at 595nm with a spectrophotometer, establishing a standard curve by combining the standard protein with G250, and then substituting the reading into the standard curve to determine the protein content after the protein to be measured is combined with G250 to develop color.

The disadvantages are mainly the structure of the special protein, the interference reagent in the buffer component, etc.

The obvious drawbacks and many limitations of the diuret and folin-phenol reagent methods have prompted scientists to search for better eggs. Take 6 test tubes and label them separately, the first 5 test tubes are added with different concentrations of standard protein solution, the last test tube is added with the protein solution to be tested, no standard protein solution is added, and the total amount of liquid in each test tube is consistent by adding distilled water.

The Bradford method, Coomassie Brilliant Blue method, was used to determine the protein content. The principle is that Coomassie Brilliant Blue is brownish-red in the ionized state, and the maximum absorbance is 488nm. When bound to a protein, it turns blue, and the protein absorbs the most light at wavelength 595 nm when bound to the pigment.

Its absorbance value is proportional to the protein content and can be used for the quantitative determination of protein.

The egg white and Coomassie brilliant blue reach equilibrium in about 2min, and the response is very rapid. The binder is stable at room temperature for 1h. The reagents prepared by this method are simple, easy to operate, and have high reaction sensitivity.

The sensitivity is 4 times higher than that of the Lowry method and can determine the protein content at the microgram level. The main disadvantage is the structure of the particular protein and the interfering agent in the buffer.

Protein is made up of amino acids and is another important energy contributor, providing 4 calories per gram of protein. But the more important role of protein is growth and metabolism. Excessive protein intake increases the burden on the kidneys.

Therefore, protein intake should be balanced between supply and demand according to nutritional status, growth and development requirements. Generally, protein intake accounts for about 20% of the total calories.

Physiological Roles of Proteins:

Growth and development, metabolism are the main roles.

It also provides calories at 4 thousand calories per gram.

Increases the burden on the kidneys.

Protein type:

Animal protein: It is the main protein of the body, such as meat, poultry and eggs, etc., these foods provide protein but also make us eat saturated fat and cholesterol and other components that are not good for the body. Therefore, lean meats, fish, skinless chicken and egg whites are the best choices, which are called "high-quality proteins".

Vegetable protein: It is another ** protein, mainly found in legumes, plant protein is low in saturated fat and cholesterol, and contains a lot of dietary fiber, and it is inexpensive, suitable for diabetic patients.

Protein is the material basis of all life, not only because protein is the basic component of the body's tissues and organs, but more importantly, protein itself is constantly synthesized and decomposed. This process of synthesis and decomposition promotes life activities, regulates the normal physiological functions of the body, and ensures the growth, development, reproduction, heredity and repair of damaged tissues of the body. According to modern biological views, proteins and nucleic acids are the main material basis of life.

Physiological functions of proteins: Proteins are important components of tissues and cells, such as muscles, bones and internal organs. The protoplasm of all cells is dominated by proteins, and the cell membranes and interstitium of animals are also mainly composed of proteins.

It is used to renew and repair tissue cells. Involved in the regulation of substance metabolism and physiological functions. Oxidation for energy.

1 gram of protein oxidizes in the body for energy about joules. Other features. Such as the physiological function of multifunctional plasma proteins.

There are more than 20 kinds of amino acids that make up proteins, and only some of them can be synthesized in the body, and the rest must be supplied by food proteins. Amino acids that cannot be synthesized in the body or are synthesized too slowly must be supplied by food proteins, so they are also called "essential amino acids". Amino acids that can be synthesized by the body do not have to be supplied by food proteins, which are also called "non-essential amino acids".

Among the many amino acids used to synthesize proteins in the body, there are 8 essential amino acids that need to be fed, namely lysine, tryptophan, phenylalanine, methionine, threonine, leucine, isoleucine and valine. The more essential amino acids a food contains, the higher its nutritional value. Animal proteins such as meat, eggs, and milk all contain 8 essential amino acids, also known as high-quality proteins; The essential amino acids contained in plant proteins such as legume proteins are incomplete.

However, if the pasta is composed of corn, millet and soybean protein mixture, its nutritional value is significantly improved. This effect of mixing several proteins with low nutritional value to improve their nutritional value is also called the complementary effect of different proteins.

Bovine trypsin allows cells to be dispersed into single cells.

Human insulin is the only hormone in the body that lowers blood sugar and the only hormone that promotes the synthesis of glycogen, fat, and protein at the same time.

Immunoglobulin action.

1) Antibody-mediated cytotoxicity.

1) Antibody-mediated cytotoxicity. (3) Antibody neutralization. (4) Damaging effect after the formation of immune complexes with antigens. (5) Sensitization of host cells or tissues, resulting in complement activation.

Human hemoglobin can carry oxygen from the lungs to tissues through arterial blood, and can carry carbon dioxide produced by tissue metabolism to the lungs through venous blood and then excreted from the body. It is known that this function is related to the two states of its subunit structure, in the hypoxic place (such as in venous blood), the subunit is in a clamping state, so that oxygen can not be combined with heme, so it can quickly remove oxygen in aerobic tissues; In the oxygen-rich lungs, the subunit structure is relaxed, allowing oxygen to bind easily to heme, which quickly transports oxygen away. The conversion of the subunit structure allows the respiratory function to proceed efficiently.

(1) Constituent organization and repair organization. Proteins are the main materials that make up tissue cells. The human brain, nerves, muscles, internal organs, blood, and even nails and hair are all made of protein.

Protein is the main component of the development and growth of the body, the renewal of aging tissues after growth, and the regeneration and repair of tissues after injury.

2) Components that make up enzymes and certain hormones.

3) Enhance the body's immunity and constitute antibodies. The strength of the body's immunity depends on the amount of antibodies against diseases.

4) Regulate osmotic pressure. In normal people, there is a constant exchange of water between plasma and tissue fluid, but it remains balanced. Its balance depends on the total amount of electrolytes and the concentration of colloidal proteins in the plasma.

When the electrolyte concentration of tissue fluid and plasma is equal, the distribution of water between the two depends on the concentration of albumin in the plasma. If there is a long-term lack of protein in the diet, the plasma egg white content decreases, and the water in the blood penetrates too much into the surrounding tissues, resulting in dystrophic edema.

5) Supply of heat energy. Although the main function of proteins in the body is not to provide heat energy, the proteins in old or damaged tissue cells are constantly broken down to release energy. In addition, if the daily intake of protein from food does not meet the needs of the human body, or the amount is excessive, it will also be oxidized and decomposed to release energy.

So protein can also provide some of the heat. It can be seen that protein is ubiquitous in the process of life activities, and has a variety of physiological functions, and is one of the important nutrients necessary for the human body.

Foods with a lot of protein include: livestock milk, such as cow's milk, goat's milk, mare's milk, etc.; Livestock meat, such as cattle, sheep, pigs, dogs, etc.; poultry meat, such as chickens, ducks, geese, quails, ostriches, etc.; Eggs, such as eggs, duck eggs, quail eggs, fish, shrimp, crabs, etc.; There are also soybeans, including soybeans, large green beans and black beans, among which soybeans have the highest nutritional value, and it is a high-quality protein in food**; In addition, dried fruits such as sesame seeds, melon seeds, walnuts, almonds, pine nuts and other dried fruits have a higher protein content. Due to the different content of amino acids in various foods, the types of amino acids contained in them, and the content of other nutrients (fats, sugars, minerals, vitamins, etc.) are also different, therefore, the above foods are all available, and foods with high protein can also be provided according to local specialties and local conditions.

Autoproteins have the functions of recognition, immunity, digestion, and transportation. It can also be digested to do energy** cell work, and it can also form some flying essential amino acids through transamination. If you consume protein, you can also supplement some essential amino acids in addition to the function.

Therefore, before drinking milk, you should eat something to keep it low, or the milk will only be absorbed as food and will not really play the role of protein.