L-cysteine, a common amino acid in organisms.Sulfur free (defined as amino acid free of sulfur in chemistry elective course 5 for senior high school students)α-One of the amino acids, which is purple in the presence of nitroprusside (colored by SH) and exists in many proteins and glutathione, can form insoluble mercaptans with Ag+, Hg+, Cu+and other metal ions.That is, R-S-M ′, R-S-M ″ - S-R (M ′, M ″ are 1-valent and 2-valent metals respectively).The molecular formula is C3H7NO2S, and the molecular weight is 121.16.Colorless crystals.Soluble in water, acetic acid and ammonia, insoluble in ether, acetone, ethyl acetate, benzene, carbon disulfide and carbon tetrachloride.It can be oxidized to cystine by air in neutral and weakly alkaline solutions.
Chinese alias: L-cysteine;L-2-amino-3-mercaptopropionic acid;(R) 2-amino-3-mercaptopropionic acid;
English name: L-Cysteine
English alias: H-CYS-OH;H-Cys-OH; CYSH; FEMA 3263; Cystein;L-Cysteine; E 920; L-Cys; CYSTEINE; (R)-2-Amino-3-mercaptopropionic acid; CYS; Thioserine;
CAS No.: 52-90-4
MDL No.: MFCD00064306
EINECS No.: 200-158-2
RTECS No.: HA1600000
BRN No.: 1721408
PubChem No.: 24901592
Molecular formula: CthreeHsevenNOtwoS
Structural type:
Molecular weight: 121.15800
Precision quality: 121.02000
PSA：102.12000
LogP：0.02840
Physicochemical properties
Appearance and property: white crystalline powder
Density: 1.334 g/cmthree
Melting point: 220 ° C (dec.) (lit.)
Boiling point: 293.9 º C at 760 mmHg
Flash point: 131.5 º C
Refractive index: 8.8 ° (C=8, 1mol/L HCl)
Water solubility: 280 g/L (25 º C)
Stability Stable, but may be air sensitiveIncompatible with oxidizing agents, bases.
Storage condition: Store at RT
security information
Customs code: 2930901000
WGK Germany：3
Hazard category code: R22;R36/37/38
Safety instructions: S36-S37/39-S26
RTECS No.: HA1600000
Dangerous goods mark: Xn[1]
toxicology data
Acute toxicity:
Oral LD50 660mg/kg (mus)
1890mg/kg(rat)
Main irritant effects:
On the skin: Irritating to the skin and mucous membrane.
Above the eyes: irritating effect.
Sensitization: No known sensitization.
Molecular structure data
1. Molar refractive index: 28.90
2. Molar volume (cm3/mol): 90.7
3. Isotonic specific volume (90.2K): 251.5
4. Surface tension (dyne/cm): 58.9
5. Polarization ratio (10-24cm3): 11.45
Calculate chemical data
1. Reference value for drainage parameter calculation (XlogP): None
2. Number of hydrogen bond donors: 3
3. Number of hydrogen bond receptors: 4
4. Number of rotatable chemical bonds: 2
5. Number of tautomers: none
6. Topological molecular polar surface area 64.3
7. Number of heavy atoms: 7
8. Surface charge: 0
9. Complexity: 75.3
10. Number of isotope atoms: 0
11. Determine the number of atomic structure centers: 1
12. Number of uncertain atomic structure centers: 0
13. Determine the number of chemical bond structural centers: 0
14. Number of indeterminate chemical bond structure centers: 0
15. Number of covalent bond units: 1[2]
synthetic method
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1. Dissolve cystine in dilute hydrochloric acid by tin particle reduction method, filter, add tin particle into the filtrate to raise temperature and reflux for 2h.Dilute the reducing solution with water, remove the remaining tin particles, saturate it with hydrogen sulfide, filter, wash the filter residue with a small amount of water, combine the washing and filtering solutions, concentrate them under reduced pressure, cool and crystallize, filter and dry to obtain L-cysteine hydrochloride.
2. Add distilled water, hydrochloric acid and cystine into the electrolytic cell for stirring and dissolution by electrolytic reduction method, and maintain the electrolysis temperature below 50 ℃ until the end point.Fill the obtained electrolyte with hydrogen sulfide for several hours and filter it.The filtrate is decolorized by adding activated carbon, filtered and concentrated under reduced pressure, cooled and crystallized, filtered and dried to obtain L-cysteine hydrochloride.
3. Synthesis: It can be hydrolyzed by protein (such as human hair) with hydrochloric acid, treated with copper oxide, and decomposed by hydrogen sulfide.It can also be obtained by the degradation of cystine.[2]
purpose
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It is mainly used in medicine, cosmetics, biochemical research, etc.It is used in bread materials to promote the formation of gluten, promote fermentation, mold, prevent aging, etc.It is used in natural fruit juice to prevent oxidation of vitamin C and browning of fruit juice.This product has detoxification effect and can be used for acrylonitrile poisoning and aromatic acid poisoning.This product also has the function of preventing radiation damage to the human body, and is also a drug for treating bronchitis, especially as a expectorant (mostly in the form of acetyl L-cysteine methyl ester). Cosmetics are mainly used for beauty lotion, perm lotion, anti sun skin cream, etc.[2]
survey
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The chemical name of cysteine (Cys) is 2-amino-3-mercaptopropionic acid, which is the polarity of aliphatic sulfhydryl groupα-amino acid.Cysteine is a conditionally necessary amino acid and raw sugar amino acid for the human body. It can be transformed from methionine (methionine, an essential amino acid for the human body) in the body and can be transformed with cystine.[3]
HSCH2CH (NH2) COOH, (C3H7NSO2) contains sulfurα-One of the amino acids, it is purple in the presence of nitroprusside (colored by SH), and exists in many proteins and glutathione. It can form insoluble mercaptans with Ag+, Hg+, Cu+and other metal ions.That is, R-S-M ′, R-S-M ″ - S-R (M ′, M ″ are 1-valent and 2-valent metals respectively).Cysteine is a nonessential amino acid.In animals, it is synthesized from methionine and serine through cystathionine.Inorganic sulfur (from sulfate) is introduced into cysteine. In plants and bacteria, H2S generated from the reduction of sulfuric acid through 3 '- adenosine phosphate 5' - phosphate sulfuric acid and sulfite is generated by reacting with O-acetylserine or serine.
Cysteine is decomposed into pyruvate, hydrogen sulfide and ammonia under anaerobic conditions through the action of hydrogen desulfurizing enzyme, or through transamination, via intermediate productsβ-Mercaptopyruvic acid is decomposed into pyruvic acid and sulfur. Under oxidation conditions, it is oxidized into cysteine sulfurous acid, which can be decomposed into pyruvic acid and sulfurous acid by transamination, and into taurine and taurine by decarboxylation.In addition, cysteine is an unstable compound, which is easy to redox and convert with cystine.It can also be condensed with toxic aromatic compounds to form mercapturic acid for detoxification.[4]
Cysteine is a naturally produced amino acid, which has many uses in food processing. It is mainly used in baking products as an essential component of dough improver
Cysteine is a reducing agent, which can promote the formation of gluten, reduce the time required for mixing and the energy required for medicine. Cysteine weakens the structure of protein by changing the disulfide bond between and within protein molecules, so that the protein will expand.
Antidote
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L-cysteine is an amino acid antidote. It participates in the reduction process of cells and the metabolism of phospholipids in the liver. It has the pharmacological effect of protecting liver cells from damage and promoting the recovery of liver function.It is mainly used for radioactive drug poisoning, heavy metal poisoning, antimony poisoning, hepatitis, toxic hepatitis, serum diseases, etc., and can prevent liver necrosis.If this product is used for the rescue of antimony poisoning, it should be given in time and in sufficient quantity to maximize the formation of non-toxic soluble complexes with antimony ions and expel them from the body.[5]
Cysteine derivatives
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Cysteine derivatives include a variety of cysteine drugs.Cysteine hydrochloride is clinically used for hepatitis and heavy metal poisoning.Cysteine is one of the natural ingredients of glutathione. Its molecule contains active sulfhydryl group (- SH), which has a protective effect on sulfhydryl protease and poisoned liver parenchyma cells, and can stimulate hematopoietic function, increase white blood cells and promote the repair of skin damage.The derivatives of cysteine, acetylcysteine, cysteine methyl ester, cysteine acetic acid and carboxymethyl cysteine, are respiratory mucus dissolvers and can promote the repair of damaged bronchial mucosa.[5]
instructions
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Usage and dosage
① Spray inhalation: only used in non emergency situations, spray inhalation with 10% solution, 1~3ml/time, 2~3 times/day.
② Tracheal instillation: during emergency treatment, 5% solution is intubated or directly instilled into the trachea, 1~2ml/time, 2~6 times/day.
③ Tracheal injection: 5% solution is injected into the trachea cavity with a syringe from the periosteum of thyroid cartilage ring of the trachea in emergency, 0.5~2ml each time (0.5ml for infants, 1ml for children, 2ml for adults).
Adverse reactions
① If the product is directly dropped into the respiratory tract, a large amount of sputum can be produced. Sputum aspirator is needed to attract and discharge sputum.
② It can cause cough, bronchospasm, nausea, vomiting, bad breath and other adverse reactions, which can be alleviated by reducing the dosage. In case of nausea and vomiting, drug administration can be suspended.Bronchospasm availableIsoproterenolMitigation.
③ The combination or alternate use of isoproterenol can improve the efficacy and reduce adverse reactions.
taboo
It is forbidden for patients with bronchial asthma.
matters needing attention
① It is not suitable to contact with metal, rubber, oxidant and oxygen, so the sprayer must be made of glass or plastic.This product should be prepared before use, and the remaining solution should be tightly sealed and stored in the refrigerator, and used up within 48 hours.
② This product can increase the excretion of gold preparation;It weakens the antibacterial activity of penicillin, tetracycline and cephalosporins, so it is not suitable to use them together.If necessary, it can be used alternately every 4 hours.
In animalsmethionineandserineafterCystathioneSynthesis.Inorganic sulfur (from sulfate) is introduced into cysteine. In plants and bacteria, it is reduced from sulfuric acid by 3 '- adenosine phosphate 5' - phosphoric acid sulfuric acid and sulfitehydrogen sulfideIt is formed by reacting with O-acetylserine or serine.
Metabolic process
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Cysteine in the body contains sulfhydryl group (- SH), whileCystinecontainDisulfide bond(- S-S -), which can be transformed into each other.When cysteine is decomposed in vivo, there are several ways:
② Thiol oxidationSulphinyl groupAnd then remove the amino group and sulfinyl group, and finally generate pyruvic acid andSulfiteThe latter can be changed into sulfuric acid after oxidation.
③ Another metabolite of cysteine is taurine, which isbile acidBile acid salt, a component of, helps to promote the digestion and absorption of lipids.
④ Cysteine is also syntheticglutamineRaw materials.glutathione(glutathion) is created byglutamate, cysteine andglycineThe tripeptidebiosynthesisNo encoded RNA is required.It is associated with an amino acid transport system called "g-glutamyl cycle".
Related products
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L-cysteineIt is a kind ofamino acidIt is the only one of more than 20 amino acids that make up proteinReducibilityThe amino acid with thiol group (- SH) has been widely used in medicine, food additives and cosmetics.In 2002, the world's demand for cysteine reached 4400-4600 tons, increasing at an annual rate of 2-3%.The growth rate of demand in Western Europe reached 3-4%, while that in Japan was 2%.At present, the production of L-cysteine mainly depends on the acid hydrolysis or alkali hydrolysis of human or animal hairL-CystineAfter, afterelectrolysisL-cysteine was prepared by reduction.This method has the advantages of low yield, high energy consumption, large amount of irritating gas generated during hydrolysis, difficult treatment of waste acid, and serious environmental pollution.With the development of L-cysteine production technology, it is produced by microbial transformationL-cysteineIt gradually replaced the hydrolysis of hair to prepare L-cysteine.Microbial transformation methodThe preparation process has attracted more and more attention due to its mild reaction conditions, strong specificity and environmental friendliness.WACKER, a German company, has successfully commercialized the production of L-cysteine by fermentation, and its annual output has reached 30% of the world's total output. It is believed that in the near future, the production of L-cysteine by hydrolysis of L-cysteine, which is the leading method in China, will become history
In addition, halfCystineIt is a naturally produced amino acid and has many uses in food processing. It is mainly used in baking products as an essential ingredient of dough improver.Cysteine is a reducing agent, which can promote the formation of gluten, reduce the time required for mixing and the energy required for medicine. Cysteine weakens the structure of protein by changing the disulfide bond between and within protein molecules, so that the protein will expand.L-CystineIt is also a necessary raw material for the production of meat flavor, and its reaction wasMaillard reaction Meat flavor is widely used in potato chips, medicine, ham sausage and other fields
Physiological function:
1. It has the conglomeration effect in the organism, so it can treat a wide range of poisons, such as formaldehydeacetaldehyde, chloroformcarbon tetrachlorideLead, cadmium, mercuric chloride, lipid peroxide, PCB, fugu poison, alcohol, etc. have effective detoxification effects, which have been proved by experiments.
2. Effectively prevent and treat radiation injury.
3. In skin proteinKeratinMaintain the activity of important sulfhydryl enzymes during production, and supplement sulfur groups to maintain the normal metabolism of skin, and regulate the bottom layer of pigment cells at the lowest layer of epidermismelaninIt is a very ideal natural whitening cosmetics.It can remove melanin from the skin itself, change the nature of the skin itself, and make the skin become naturally white.
4. Whenever inflammation and allergy reduce sulfhydryl enzymes such as cholinesterase, L-cysteine supplementation can maintain the activity of sulfhydryl enzymes and improve the skin symptoms of inflammation and allergy.
5. With dissolutionCutinTherefore, it is also effective for keratosis.
6. It has the function of preventing organism from aging.
7. It is mainly distributed in the liver, spleen and kidney, and also accumulates on the surface of the human body, including the skin, mucous membrane, and digestive organ. When foreign bodies, including those ingested through the mouth, inhaled from the atmosphere, and intruded in contact with the skin, invade, it can strengthen the defense ability of the organism itself and adjust the defense mechanism of the organism.
