Glycine, also known as glycine, is a kind ofNonessential amino acid, the chemical formula is CtwoHfiveNOtwo。Glycine is an endogenous antioxidantReduced glutathioneIt is composed of amino acids, and is often supplemented by external sources in case of severe stress, sometimes calledSemiessential amino acid。[1]Glycine is one of the simplest amino acids.[4]
Solid glycine is a white to grayish white crystalline powder, odorless and non-toxic[2]。Soluble in water, soluble inethanolorEtherIt is almost insoluble.It is used in pharmaceutical industry, biochemical test and organic synthesis. It is a kind of amino acid with the simplest structure in the amino acid series and is not necessary for human body. It has both acidic and basic functional groups in the molecule, can be ionized in water, and has very strongHydrophilicity, but it belongs to non-polar amino acid, soluble in polar solvent, but insoluble inNon-polar solvent[3]It also has a high boiling point and melting point, and glycine can take on different molecular forms through the adjustment of the acidity and alkalinity of the aqueous solution.
Solubility: easily soluble in water, slightly soluble in pyridine, almost insoluble in ethanol and ether
Three dimensional spherical chain structure of glycine
Glycine is a polar molecule on the whole (all amino acids are polar), but it belongs to non-polar amino acids.This is because the polarity of an amino acid is judged based on the nature of its R group, not the whole molecule.Glycine branch chain is a hydrogen atom, which is classified as a hydrocarbon chain, which is non-polar.Similarly, although it is easily soluble in water, it is a hydrophobic amino acid.
Of course, some people think that the side chain of glycine is between polarity and non polarity, and its R group is only a hydrogen atom, which has little effect on the amino and carboxyl groups with strong polarity.However, it is generally classified as non-polar in biology.
Molecular structure data
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Molar refractive index: 16.41
Molar volume (cmthree/mol）59.8
Isotonic specific volume (90.2K): 162.5
Surface tension (dyne/cm): 54.4
Polarization (10-24cmthree）：6.50
Calculate chemical data
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Reference value for drainage parameter calculation (XlogP): None
Number of hydrogen bond donors: 2
Number of hydrogen bond receptors: 3
Number of rotatable chemical bonds: 1
Number of tautomers: 0
Topological molecular polar surface area: 63.3
Number of heavy atoms: 5
Surface charge: 0
Complexity: 42.9
Number of isotope atoms: 0
Determine the number of atomic structure centers: 0
Number of uncertain atomic structure centers: 0
Determine the number of chemical bond structure centers: 0
Number of uncertain chemical bond structure centers: 0
Number of covalent bond units: 1[6]
synthetic method
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Strecker method
Using formaldehyde, hydrogen cyanide and ammonia as raw materials, aminoacetonitrile was first synthesized, and then decomposed to glycine.
The crude hydrogen cyanide is synthesized from methane and ammonia, and then the formaldehyde solution continuously absorbs the hydrogen cyanide. Then the reaction solution and ammonia are reacted at 120 ℃ for 2 min to produce aminoacetonitrile. Finally, alkali solution is added to hydrolyze to obtain glycine with an overall yield of 87%.
Bucherer method
Add melamine into the aqueous solution of ammonium carbonate and sodium cyanide, stir and dissolve it at room temperature, and then react for 3h at 80-85 ℃.Get hydantoin aqueous solution.Then directly add 30% NaOH aqueous solution and hydrolyze it at 170 ℃ for 3h.Finally, glycine was treated with cation exchange resin, and the yield was 83.2%.
Ammoniation of monochloroacetic acid
Heat ammonia water and ammonium bicarbonate to 55 ℃, add monochloroacetic acid hydrolysis solution to react for 2h.Then raise the temperature to 80 ℃ to remove the remaining ammonia, and decolorize with activated carbon.After filtration, add 95% ethanol to the filtrate to precipitate glycine crystals.Wash with ethanol after separation.After drying, crude products are obtained.The crude product is dissolved in hot water and recrystallized with ethanol to obtain the finished product with a yield of about 42%.
Phase transfer catalysis
Add 2kg ammonia into 1L methanol, and then add 0.3kg hexamethylene tetramine. After the solution is clarified, add 2L methanol dissolved in 10kg chloroacetic acid. The system temperature rises significantly, and when it reaches 58 ℃, there is a large amount of crystallization.When the temperature drops to room temperature and the upper liquid is clear, the crystal is obtained by filtration. After the filtrate is placed for 2 days, some crystals can be separated.Add 2-3 times the amount of deionized water into the crude product, heat it to 70-75 ℃, dissolve it, add methanol twice the volume, cool it, precipitate and crystallize, dry it at 70 ℃ for 2h, and obtain high-quality product with yield of 68.6% and purity of 99.6%
Biological methods
In the late 1980s, Mitsubishi Corporation of Japan added the screened aerobic Agrobacterium, Brevibacterium, Corynebacterium and other microbial strains to the medium containing carbon source, nitrogen source and inorganic nutrient solution for cultivation, and then converted ethanolamine into glycine at 25~45 ℃ and pH 4~9,Glycine is obtained by concentrated neutralization ion exchange treatment.
Since the 1990s, the technology of glycine synthesis abroad has made new progress.Nitto Chemical Industry Co., Ltd. of Japan added 0.5% (mass fraction, dry weight) of cultivated Pseudomonas, Casein, Alcaligenes and other bacteria to the substrate containing glycine amine, reacted for 45 h at 30 ℃, pH 7.9~8.1, and almost all glycine amines were hydrolyzed to glycine, with a conversion rate of 99%.
purpose
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food
1. It can be used as biochemical reagent, medicine, feed and food additive, and nitrogen fertilizer industry can be used as non-toxic decarbonization agent;
2. As a nutritional supplement, it is mainly used in flavoring and other aspects;
3. It can inhibit the reproduction of Bacillus subtilis and Escherichia coli to a certain extent, so it can be used as a preservative for surimi products, peanut butter, etc., with the addition amount of 1%~2%;
4. It has antioxidant effect (making use of its metal chelation), and can extend the storage life of cream, cheese and margarine by 3~4 times;
5. To stabilize lard in baked food, 2.5% glucose and 0.5% glycine can be added;
6. Adding 0.1%~0.5% wheat flour for instant noodles can also serve as seasoning;
7. It can buffer the taste of salt and vinegar. The added amount is 0.3%~0.7% for salt pickled products and 0.05%~0.5% for acid pickled products;
8. It can be used as spice according to GB2760-96.
medicine
1. Used as medicine for medical microbiology and biochemical amino acid metabolism research;
2. It is used as a raw material for synthesis of chlortetracycline buffer anti Parkinson's disease drug L-dopa vitamin B6 and amino acids such as threonine;
3. Treatment of myasthenia gravis and progressive muscular atrophy;
4. Treatment of gastrodiesteremia, chronic enteritis (often combined with antacids);
5. Combined with aspirin, it can reduce the irritation to the stomach;
6. Treatment of hyperprolinemia in children;
7. As a nitrogen source for generating nonessential amino acids, it is added to the mixed amino acid injection.
Agriculture
1. It is mainly used as an additive and attractant to increase amino acids in feed for poultry, livestock and poultry, especially pets.Used as protein hydrolysate additive and synergist of protein hydrolysate;
2. Glycine ethyl ester hydrochloride, an intermediate used in the synthesis of pyrethroid insecticides, can also be used in the production of pesticides to synthesize the fungicide isoprothiolane and the herbicide solid glyphosate.
Industry
1. Used as an additive in electroplating solution;
2. Used in pharmaceutical industry, biochemical test and organic synthesis;
3. Used as raw material of cephalosporin, intermediate of thiamphenicol, intermediate of imidazole acetic acid, etc;
4. Used as cosmetic raw material.
reagent
1. It is used for peptide synthesis and as amino acid protection monomer;
2. It is used for the preparation of tissue culture medium and the inspection of copper, gold and silver;
3. Because glycine is a zwitterion with amino and carboxyl groups, it has strong buffering property and is often used as a buffer solution;
4. Used as complexometric titration indicator and solvent.
Use limit
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According to GB 2760-2014 food additive use standard, glycine, CNS No. 12.007, can be used as a flavor enhancer in prefabricated meat products, cured meat products (such as bacon, bacon, salted duck, Chinese ham, sausages), cooked meat products, stewed meat products, white boiled meat, stewed meat, fermented grains meat, smoked, roasted, fried meatWestern style ham (smoked and roasted, smoked and boiled ham), meat sausage, fermented meat products, dried cooked meat products, dried meat floss, dried meat, preserved meat, canned meat, other cooked meat products, condiments, flavor agents and fresheners, vinegar, brewing vinegar, vinegar, sauce oil, brewing soy sauce, soy sauce, soy sauce and soy sauce products, brewing sauce, soy sauce, soy sauce, cooking wine and productsCompound seasoning, solid compound seasoning, solid soup, chicken essence, chicken powder, other solid compound seasoning, semi-solid compound seasoning, mayonnaise, salad sauce, seasoning based on animal raw materials, seasoning based on vegetables, other semi-solid compound seasoning, liquid compound seasoning (excluding 12.03, 12.04), concentrated soup (canned, bottled)Broth, bone soup, seasoning clear juice, oyster sauce, shrimp oil, fish sauce, etc., other condiments, fruit and vegetable juice (pulp) drinks, vegetable protein drinks.
Among them, in the pre fabricated meat products, conditioned meat products (raw meat with conditioning materials added), cured meat products (such as bacon, bacon, salted duck, Chinese ham, sausages), cooked meat products, soy sauce products, white boiled meat, soy sauce meat, fermented grains meat, smoked, roasted, roasted meat, fried meat, western ham (smoked, smoked, steamed and boiled ham), meat sausageThe maximum use limit of fermented meat products, dried cooked meat products, loose meat products, dried meat products, preserved meat products, canned meat products and other cooked meat products is 3.0g/kg.In condiments, fresheners and fresheners, vinegar, brewing vinegar, preparing vinegar, soy sauce, brewing soy sauce, preparing soy sauce, sauce and sauce products, brewing sauce, preparing sauce, cooking wine and products, compound condiments, solid compound condiments, solid soup, chicken essence, chicken powder, other solid compound condiments, semi-solid compound condiments, mayonnaise, salad dressingSeasoning paste based on animal raw materials, seasoning paste based on vegetables, other semi-solid compound seasonings, liquid compound seasonings (excluding 12.03, 12.04), concentrated soup (canned, bottled), broth, bone soup, seasoning clear juice, oyster sauce, shrimp oil, fish sauce, other seasonings, fruit and vegetable juice (pulp) drinksThe maximum use limit of vegetable protein beverage is 1.0g/kg.[5]
Pharmacopoeia information
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essential information
This product is aminoacetic acid, calculated as dry product, containing CtwoHfiveNOtwoNot less than 99.0%.
character
This product is white to almost white crystalline powder, odorless.
This product is easily soluble in water, but almost insoluble in ethanol or ether.
identify
1. Take appropriate amount of this product and glycine reference substance, add water to dissolve and dilute them respectively to prepare a solution containing about 10mg per 1mL, which is used as the test solution and reference solution.According to the chromatographic conditions under other amino acids, the position and color of the main spot of the test solution should be the same as that of the control solution.
2. The infrared absorption spectrum of this product should be consistent with the control spectrum (spectrum set 929 figure).
inspect
acidity
Take 1.0g of this product, add 20mL of water to dissolve it, and then measure it according to the law (general rule 0631). The pH value should be 5.6~6.6.
Transmittance of solution
Take 1.0g of this product, add 20mL of water to dissolve it, and then measure the transmittance at 430nm by ultraviolet visible spectrophotometry (general rule 0401), which shall not be less than 98.0%.
chloride
Take 1.0g of this product and check it according to the law (general rule 0801). Compared with the reference solution made of 7.0mL of standard sodium chloride solution, it should not be more concentrated (0.007%).
sulfate
Take 2.5g of this product and check it according to the law (general rule 0802). Compared with the control solution made of 1.5mL of standard potassium sulfate solution, it should not be more concentrated (0.006%).
ammonium salt
Take 0.10g of this product and check it according to the law (general rule 0808). Compared with the control solution made of 2.0mL of standard ammonium chloride solution, it should not be deeper (0.02%).
Other amino acids
Test according to thin layer chromatography (general rule 0502).
Test solution: take this product, add water to dissolve and dilute it to make a solution containing about 10mg per 1mL.
Reference solution: precisely measure 1mL of the test solution, place it in a 200mL volumetric flask, dilute it with water to the scale, and shake it up.
System suitability solution: Take appropriate amount of glycine reference substance and alanine reference substance, place them in the same measuring flask, add water to dissolve and dilute them to make a solution containing about 10mg and 0.05mg per 1mL respectively.
Chromatographic conditions: silica gel G thin layer plate is used, and n-propanol ammonia (7:3) is used as developing agent.
Determination method: Pipet 2 µ L of each of the three solutions mentioned above, dab them on the same thin plate, spread them for about 10cm, dry them in the air, dry them at 80 ° C for 30 minutes, spray n-propanol solution of ninhydrin (0 → 100), heat them at 105 ° C until spots appear, and inspect them immediately.
System suitability requirements: the reference solution should show a clear spot, and the system suitability solution should show two completely separated spots.
Limit: Except for the main spot, the number of impurity spots in the test solution shall not exceed 1, and its color shall not be deeper (0.5%) than the main spot in the control solution.
Loss on drying
Take this product and dry it at 105 ℃ for 3 hours. The weight loss shall not exceed 0.2% (general rule 0831).
Ignition residue
Not more than 0.1% (general rule 0841).
ferric salt
Take 1.50g of this product and check it according to the law (general rule 0807). Compared with the control solution made of 1.5mL of standard iron solution, it should not be deeper (0.001%).
heavy metal
Take 2.0g of this product, add 23mL of water to dissolve it, add 2mL of acetate buffer solution (pH 3.5), and check according to the law (General Rule 0821, Method 1). The content of heavy metals should not exceed 10 parts per million.
Arsenite
Take 2.0g of this product, add 23mL of water to dissolve it, add 5mL of hydrochloric acid, and check according to the law (the first method of general rule 0822), which should meet the requirements (0.0001%).
Bacterial endotoxin
Take this product and check it according to the law (general rule 1143). The amount of endotoxin in every 1g of glycine should be less than 20EU (for injection).
Assay
Take about 70mg of this product, precisely weigh it, add 1.5mL of anhydrous formic acid to dissolve it, add 50mL of glacial acetic acid, titrate it with perchloric acid titrant (0.1mol/L) according to the potentiometric titration method (General Rule 0701), and correct the titration result with a blank test. Every 1mL of perchloric acid titrant (0.1mol/L) is equivalent to 7.507mg of CtwoHfiveNOtwo。
