|Amino acids with the simplest structure
|Glycine is of the simplest structure in the 20 members of amino acid series, also known as amino acetate. It is a non-essential amino acid for the human body and contains both acidic and basic functional group inside its molecule. It exhibits as a strong electrolyte an aqueous solution, and has a large solubility in strong polar solvents but almost insoluble in non-polar solvents. Moreover, it also has a relative high melting point and boiling point. The adjustment of the pH of the aqueous solution can make glycine exhibit different molecular forms. The side chain of glycine contains only a hydrogen atom. Owing to another hydrogen atom connecting to the α-carbon atom, the glycine is not optical isomer. Since the side bond of glycine is very small, it can occupy space which can’t be occupied by other amino acids, such as those amino acids located within the collagen helix. At room temperature, it exhibits as white crystal or light yellow crystalline powder and has a unique sweet taste which can ease the taste of acid and alkaline taste, masking the bitter taste of saccharin in food and enhance the sweetness. However, if an excessive amount of glycine is absorbed by body, they not only can’t be totally absorbed by the body, but will also break the balance of the body's absorption of amino acids as well as affect the absorption of other kinds of amino acids, leading to nutrient imbalances and negatively affected health. The milk drink with glycine being the major raw material can easily does harm to the normal growth and development of young people and children. It has a density of 1.1607, melting point of 232~236 °C (decomposition). It is soluble in water but insoluble in alcohol and ether. It is capable of acting together with hydrochloric acid to form hydrochloride salt. It is presented in the muscles of animals. IT can be produced from the reaction between monochloro acetate and ammonium hydroxide as well as from the hydrolysis of gelation with further refining.
|History of discovery
|Amino acids are organic acids containing an amino group and are the basic units of protein. They are generally colorless crystals with a relative high melting point (over 200 °C). It is soluble in water with amphiprotic ionization characteristics and can have sensitive colorimetric reaction with ninhydrin reagent. In 1820, glycine with the simplest structure was first discovered in a protein hydrolysis product. Until 1940, it has been found that there were about 20 kinds of amino acids in nature. They are necessary for the protein synthesis of both human and animal. They are mostly α-L-type amino acids. According to the different number of amino groups and carboxyl groups contained in amino acids, we classify amino acids into neutral amino acids (glycine, leucine, isoleucine, valine, cystine, cysteine, A methionine, threonine, serine, phenylalanine, tyrosine, tryptophan, proline and hydroxyproline, etc.) with the amino acid molecules containing only one amino group and a carboxyl group; acidic amino acid (glutamate, aspartate) which contains two carboxyl and one amino group; alkaline amino acids (lysine, arginine) which molecularly contains one carboxyl group and two amino groups; Histidine contains a nitrogen ring which exhibits weakly alkaline and thus also belonging to alkaline amino acids. Amino acids can be obtained both from protein hydrolysis and from chemical synthesis. Since the 1960s, industrial production mainly applied microbial fermentation, such as monosodium glutamate factory has been widely applied fermentation method for production of glutamate. In recent years, people has also applied petroleum hydrocarbons and other chemical products as raw materials of fermentation for production of amino acids.
The above information is edited by the Chemicalbook of Dai Xiongfeng.
|Accurately weigh 175 mg of sample which has undergone drying for 2 h at 105 °C and place it in a 250m1 flask, add 50 mL of glacial acetic acid for dissolving; add 2 drops of crystal violet test solution (TS-74); titrate with 0.1ml/L perchloric acid to blue-green endpoint. At the same time carry out a blank test, and make the necessary corrections. Each mL of 0.1mol/L perchloric acid is equivalent to glycine (C2H5NO2) 7.507mg.
|Biosynthesis of glycine production
|In the late 1980s, Japan's Mitsubishi Corporation added the screened aerobic Agrobacterium, Brevibacterium, Corynebacterium genus to the medium containing carbon, nitrogen and inorganic nutrient solution for cultivation, and then applied this class of bacteria for converting ethanolamine to glycine in 25~45 °C and pH value from 4 to 9 and further applied concentration, neutralization ion exchange treatment to get the glycine product.
After entering the 1990s, there had been new progress on the production technology of glycine in foreign countries. The Nitto Chemical Industry Co (Japan) add cultured pseudomonas genus, casein bacteria genus, and alcaligenes genus and other species in 0.5% (mass fraction, dry weight) to the glycine amine-containing matrix for reaction of 45 h under 30 °C and pH value of 7.9 to 8.1 with almost all glycine amine being hydrolyzed into glycine with the conversion rate of 99%. Although biological methods are still in the research stage, however, owing to its high selectivity, non-pollution property, it will be a synthetic route with highly development potential.
- Used for the pharmaceutical industry, organic synthesis and biochemical analysis.
- Used as a buffer for the preparation of tissue culture media and the testing of copper, gold and silver. In medicine, it is used for the treatment of myasthenia gravis and progressive muscular atrophy, hyperacidity, chronic enteritis, and children hyperprolinemia diseases.
- Used for the treatment of myasthenia gravis and progressive muscular atrophy; treatment of excess stomach acid ester disease, chronic enteritis (often in combination antacid); using in combination with aspirin can reduce the irritation of the stomach; treatment of children hyperprolinemia; as the nitrogen source for generating non-essential amino acid and can be added to a mixed amino acid injection.
- Glycine is primarily used as a nutritional additive in chicken feed.
- Used as a kind of nutritional supplement which is mainly used for flavoring.
- Flavoring agent: Used for alcoholic beverage in combination with ; the addition amount: grape wine: 0.4%, whiskey: 0.2%, champagne: 1.0%. Others such as powder soup: 2%; lees marinated foods: 1%. Because it is tasted like shrimp and cuttlefish, and thus can be used in sauces.
- It has some certain inhibitory effects on the Bacillus subtilis and E. coli and thus can be used as the preservatives of surimi products and peanut butter with the added amount being 1% to 2%.
- Buffering effect: Because glycine is amphiprotic ions containing both amino and carboxyl groups, it has a strong buffering property on the taste feeling of salt and vinegar. The added amount is: salted products: 0.3% to 0.7%, acid stain product: 0.05% to 0.5%. Antioxidant effect (with its metal chelation): being added to butter, cheese, and margarine extend the storage duration by 3 to 4 times. To make the lard oil in baked food be stable, we can add 2.5% glucose and 0.5% glycine. Adding 0.1% to 0.5% glycine to the wheat flour for making convenient noodles can play a role of flavoring. In pharmacy, it is used as antacids (hyperacidity), therapeutic agent for muscle nutritional disorder as well as antidotes. Moreover, glycine can also be used as the raw material for synthesizing amino acids like threonine.
- It can be used as a spice according to the provisions of GB 2760-96.
- Glycine is also known as aminoacetic acid. In the field of pesticide production, it is used for synthesizing the glycine ethyl ester hydrochloride which is the intermediate for the synthesis of pyrethroid insecticides. Moreover, it can also be used for synthesizing fungicides iprodione and solid glyphosate herbicide; in addition it is also used in various kinds of other industries such as fertilizer, medicine, food additives, and spices.
- Used as a solvent to remove carbon dioxide in the fertilizer industry. In the pharmaceutical industry, it can be used as amino acid preparations, the buffer of chlortetracycline buffer and as the raw material for synthesizing the anti-Parkinson's disease drugs L-dopa. Moreover, it is also the intermediate for producing ethyl imidazole. It is also an adjunct therapy medicine for treating neural hyperacidity and effectively suppressing excess amount of gastric ulcer acid. In the food industry, it is used for the synthesis of alcohol, brewing products, meat processing and cold drinks formula. As a food additive, glycine can be used alone as a condiment and also used in combination with sodium glutamate, DL-alanine acid, and citric acid. In other industries, it can be used as a pH adjusting agent, being added to the plating solution, or used as the raw material for making other amino acids. It can further be used as biochemical reagents and solvent in organic synthesis and biochemistry.
- Used as the intermediates of pharmaceutical and pesticide, decarbonation solvents of fertilizers, plating fluid, etc.
- Used as a solvent for removing carbon dioxide in the fertilizer industry. In pharmaceutical industry, it is used as the buffer of chlortetracycline, amino antacids, and used for the preparation of L-dopa. In food industry, it can be used as flavoring agents, agent for removing saccharine bitter taste, for brewing, meat processing, and preparation of soft drinks. In addition, it can also be used as a pH adjusting agent and used in the preparation of the plating solution.
- Used as biochemical reagents for the pharmaceutical, food and feed additives; it can also be used as a non-toxic decarbonization agent in the field of fertilizer industry.