Glycine

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Glycine [1]
Glycine-2D-skeletal.png
Skeletal formula of neutral glycine
Glycine-zwitterion-2D-skeletal.png
Skeletal formula of zwitterionic glycine
Glycine-neutral-Ipttt-conformer-3D-bs-17.png
Ball-and-stick model of the gas-phase structure
Glycine-zwitterion-from-xtal-3D-bs-17.png
Ball-and-stick model of the zwitterionic solid-state structure
Glycine-neutral-Ipttt-conformer-3D-sf.png
Space-filling model of the gas-phase structure
Glycine-zwitterion-from-xtal-3D-sf.png
Space-filling model of the zwitterionic solid-state structure
Names
IUPAC name
Aminoacetic acid [2]
Systematic IUPAC name
2-Aminoethanoic acid
Other names
Aminoethanoic acid, Glycocol
Identifiers
3D model (JSmol)
AbbreviationsGly, G
ChEBI
ChEMBL
ChemSpider
DrugBank
ECHA InfoCard 100.000.248 OOjs UI icon edit-ltr-progressive.svg
EC Number
  • 200-272-2
  • (HCl):227-841-8
KEGG
PubChem CID
UNII
  • InChI=1S/C2H5NH2/c3-1-2(4)5/h1,3H2,(H,4,5) Yes check.svgY
    Key: DHMQDGOQFOQNFH-UHFFFAOYSA-N Yes check.svgY
  • InChI=1S/C2H5NO2/c3-1-2(4)5/h1,3H2,(H,4,5)
    Key: DHMQDGOQFOQNFH-UHFFFAOYAW
Properties
C2H5NO2
Molar mass 75.067 g·mol−1
AppearanceWhite solid
Density 1.1607 g/cm3 [3]
Melting point 233 °C (451 °F; 506 K) (decomposition)
24.99 g/100 mL (25 °C) [4]
Solubility soluble in pyridine
sparingly soluble in ethanol
insoluble in ether
Acidity (pKa)2.34 (carboxyl), 9.6 (amino) [5]
-40.3·10−6 cm3/mol
Pharmacology
B05CX03 ( WHO )
Hazards
Lethal dose or concentration (LD, LC):
2600 mg/kg (mouse, oral)
Supplementary data page
Glycine (data page)
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Yes check.svgY  verify  (what is  Yes check.svgYX mark.svgN ?)

Glycine (symbol Gly or G; [6] /ˈɡlaɪsiːn/ ( Loudspeaker.svg listen )) [7] is an amino acid that has a single hydrogen atom as its side chain. It is the simplest stable amino acid (carbamic acid is unstable), with the chemical formula NH2‐CH2‐COOH. Glycine is one of the proteinogenic amino acids. It is encoded by all the codons starting with GG (GGU, GGC, GGA, GGG). Glycine is integral to the formation of alpha-helices in secondary protein structure due to its compact form. For the same reason, it is the most abundant amino acid in collagen triple-helices. Glycine is also an inhibitory neurotransmitter – interference with its release within the spinal cord (such as during a Clostridium tetani infection) can cause spastic paralysis due to uninhibited muscle contraction.

It is the only achiral proteinogenic amino acid. It can fit into hydrophilic or hydrophobic environments, due to its minimal side chain of only one hydrogen atom.

History and etymology

Glycine was discovered in 1820 by French chemist Henri Braconnot when he hydrolyzed gelatin by boiling it with sulfuric acid. [8] He originally called it "sugar of gelatin", [9] [10] but French chemist Jean-Baptiste Boussingault showed in 1838 that it contained nitrogen. [11] In 1847 American scientist Eben Norton Horsford, then a student of the German chemist Justus von Liebig, proposed the name "glycocoll"; [12] [13] however, the Swedish chemist Berzelius suggested the simpler current name a year later. [14] [15] The name comes from the Greek word γλυκύς "sweet tasting" [16] (which is also related to the prefixes glyco- and gluco- , as in glycoprotein and glucose ). In 1858, the French chemist Auguste Cahours determined that glycine was an amine of acetic acid. [17]

Production

Although glycine can be isolated from hydrolyzed protein, this route is not used for industrial production, as it can be manufactured more conveniently by chemical synthesis. [18] The two main processes are amination of chloroacetic acid with ammonia, giving glycine and ammonium chloride, [19] and the Strecker amino acid synthesis, [20] which is the main synthetic method in the United States and Japan. [21] About 15 thousand tonnes are produced annually in this way. [22]

Glycine is also cogenerated as an impurity in the synthesis of EDTA, arising from reactions of the ammonia coproduct. [23]

Chemical reactions

Its acid–base properties are most important. In aqueous solution, glycine is amphoteric: below pH = 2.4, it converts to the ammonium cation called glycinium. Above about 9.6, it converts to glycinate.

Glycine-protonation-states-2D-skeletal.png

Glycine functions as a bidentate ligand for many metal ions, forming amino acid complexes. A typical complex is Cu(glycinate)2, i.e. Cu(H2NCH2CO2)2, which exists both in cis and trans isomers.

With acid chlorides, glycine converts to the amidocarboxylic acid, such as hippuric acid [24] and acetylglycine. [25] With nitrous acid, one obtains glycolic acid (van Slyke determination). With methyl iodide, the amine becomes quaternized to give trimethylglycine, a natural product:

H
3N+
CH
2COO−
 + 3 CH3I → (CH
3)
3N+
CH
2COO−
 + 3 HI

Glycine condenses with itself to give peptides, beginning with the formation of glycylglycine:

2 H
3N+
CH
2COO−
 → H
3N+
CH
2CONHCH
2COO−
 + H2O

Pyrolysis of glycine or glycylglycine gives 2,5-diketopiperazine, the cyclic diamide.

It forms esters with alcohols. They are often isolated as their hydrochloride, e.g., glycine methyl ester hydrochloride. Otherwise the free ester tends to convert to diketopiperazine.

As a bifunctional molecule, glycine reacts with many reagents. These can be classified into N-centered and carboxylate-center reactions.

Metabolism

Biosynthesis

Glycine is not essential to the human diet, as it is biosynthesized in the body from the amino acid serine, which is in turn derived from 3-phosphoglycerate, but the metabolic capacity for glycine biosynthesis does not satisfy the need for collagen synthesis. [26] In most organisms, the enzyme serine hydroxymethyltransferase catalyses this transformation via the cofactor pyridoxal phosphate: [27]

serine + tetrahydrofolate → glycine + N5,N10-methylene tetrahydrofolate + H2O

In the liver of vertebrates, glycine synthesis is catalyzed by glycine synthase (also called glycine cleavage enzyme). This conversion is readily reversible: [27]

CO2 + NH+
4 + N5,N10-methylene tetrahydrofolate + NADH + H+ ⇌ Glycine + tetrahydrofolate + NAD+

In addition to being synthesized from serine, glycine can also be derived from threonine, choline or hydroxyproline via inter-organ metabolism of the liver and kidneys. [28]

Degradation

Glycine is degraded via three pathways. The predominant pathway in animals and plants is the reverse of the glycine synthase pathway mentioned above. In this context, the enzyme system involved is usually called the glycine cleavage system: [27]

Glycine + tetrahydrofolate + NAD+ ⇌ CO2 + NH+
4 + N5,N10-methylene tetrahydrofolate + NADH + H+

In the second pathway, glycine is degraded in two steps. The first step is the reverse of glycine biosynthesis from serine with serine hydroxymethyl transferase. Serine is then converted to pyruvate by serine dehydratase. [27]

In the third pathway of its degradation, glycine is converted to glyoxylate by D-amino acid oxidase. Glyoxylate is then oxidized by hepatic lactate dehydrogenase to oxalate in an NAD+-dependent reaction. [27]

The half-life of glycine and its elimination from the body varies significantly based on dose. [29] In one study, the half-life varied between 0.5 and 4.0 hours. [29]

Glycine is extremely sensitive to antibiotics which target folate, and blood glycine levels drop severely within a minute of antibiotic injections. Some antibiotics can deplete more than 90% of glycine within a few minutes of being administered. [30]

Physiological function

The principal function of glycine is it acts as a precursor to proteins. Most proteins incorporate only small quantities of glycine, a notable exception being collagen, which contains about 35% glycine due to its periodically repeated role in the formation of collagen's helix structure in conjunction with hydroxyproline. [27] [31] In the genetic code, glycine is coded by all codons starting with GG, namely GGU, GGC, GGA and GGG.

As a biosynthetic intermediate

In higher eukaryotes, δ-aminolevulinic acid, the key precursor to porphyrins, is biosynthesized from glycine and succinyl-CoA by the enzyme ALA synthase. Glycine provides the central C2N subunit of all purines. [27]

As a neurotransmitter

Glycine is an inhibitory neurotransmitter in the central nervous system, especially in the spinal cord, brainstem, and retina. When glycine receptors are activated, chloride enters the neuron via ionotropic receptors, causing an inhibitory postsynaptic potential (IPSP). Strychnine is a strong antagonist at ionotropic glycine receptors, whereas bicuculline is a weak one. Glycine is a required co-agonist along with glutamate for NMDA receptors. In contrast to the inhibitory role of glycine in the spinal cord, this behaviour is facilitated at the (NMDA) glutamatergic receptors which are excitatory. [32] The LD50 of glycine is 7930 mg/kg in rats (oral), [33] and it usually causes death by hyperexcitability.

Uses

In the US, glycine is typically sold in two grades: United States Pharmacopeia (“USP”), and technical grade. USP grade sales account for approximately 80 to 85 percent of the U.S. market for glycine. If purity greater than the USP standard is needed, for example for intravenous injections, a more expensive pharmaceutical grade glycine can be used. Technical grade glycine, which may or may not meet USP grade standards, is sold at a lower price for use in industrial applications, e.g., as an agent in metal complexing and finishing. [34]

Animal and human foods

Structure of cis-Cu(glycinate)2(H2O) Cu(gly)2(OH2).png
Structure of cis-Cu(glycinate)2(H2O)

Glycine is not widely used in foods for its nutritional value, except in infusions. Instead glycine's role in food chemistry is as a flavorant. It is mildly sweet, and it counters the aftertaste of saccharine. It also has preservative properties, perhaps owing to its complexation to metal ions. Metal glycinate complexes, e.g. copper(II) glycinate are used as supplements for animal feeds. [22]

The U.S. "Food and Drug Administration no longer regards glycine and its salts as generally recognized as safe for use in human food". [36]

Chemical feedstock

Glycine is an intermediate in the synthesis of a variety of chemical products. It is used in the manufacture of the herbicides glyphosate, [37] iprodione, glyphosine, imiprothrin, and eglinazine. [22] It is used as an intermediate of the medicine such as thiamphenicol.[ citation needed ]

Laboratory research

Glycine is a significant component of some solutions used in the SDS-PAGE method of protein analysis. It serves as a buffering agent, maintaining pH and preventing sample damage during electrophoresis. Glycine is also used to remove protein-labeling antibodies from Western blot membranes to enable the probing of numerous proteins of interest from SDS-PAGE gel. This allows more data to be drawn from the same specimen, increasing the reliability of the data, reducing the amount of sample processing, and number of samples required. This process is known as stripping.

Presence in space

The presence of glycine outside the earth was confirmed in 2009, based on the analysis of samples that had been taken in 2004 by the NASA spacecraft Stardust from comet Wild 2 and subsequently returned to earth. Glycine had previously been identified in the Murchison meteorite in 1970. [38] The discovery of glycine in outer space bolstered the hypothesis of so called soft-panspermia, which claims that the "building blocks" of life are widespread throughout the universe. [39] In 2016, detection of glycine within Comet 67P/Churyumov–Gerasimenko by the Rosetta spacecraft was announced. [40]

The detection of glycine outside the Solar System in the interstellar medium has been debated. [41] In 2008, the Max Planck Institute for Radio Astronomy discovered the spectral lines of a glycine precursor (aminoacetonitrile) in the Large Molecule Heimat, a giant gas cloud near the galactic center in the constellation Sagittarius. [42]

Evolution

Glycine is proposed to be defined by early genetic codes. [43] [44] [45] [46] For example, low complexity regions (in proteins), that may resemble the proto-peptides of the early genetic code are highly enriched in glycine. [46]

Presence in foods

Food sources of glycine [47]
Foodg/100g
Snacks, pork skins 11.04
Sesame seeds flour (low fat)3.43
Beverages, protein powder (soy-based)2.37
Seeds, safflower seed meal, partially defatted2.22
Meat, bison, beef and others (various parts)1.5-2.0
Gelatin desserts1.96
Seeds, pumpkin and squash seed kernels1.82
Turkey, all classes, back, meat and skin1.79
Chicken, broilers or fryers, meat and skin1.74
Pork, ground, 96% lean / 4% fat, cooked, crumbles1.71
Bacon and beef sticks1.64
Peanuts 1.63
Crustaceans, spiny lobster1.59
Spices, mustard seed, ground1.59
Salami 1.55
Nuts, butternuts, dried1.51
Fish, salmon, pink, canned, drained solids1.42
Almonds 1.42
Fish, mackerel 0.93
Cereals ready-to-eat, granola, homemade0.81
Leeks, (bulb and lower-leaf portion), freeze-dried0.7
Cheese, parmesan (and others), grated0.56
Soybeans, green, cooked, boiled, drained, without salt0.51
Bread, protein (includes gluten)0.47
Egg, whole, cooked, fried0.47
Beans, white, mature seeds, cooked, boiled, with salt0.38
Lentils, mature seeds, cooked, boiled, with salt0.37

GlyNAC

In 2022, researchers report that the widely used supplements glycine and N-Acetylcysteine (NAC) when combined as "GlyNAC", which previously showed various beneficial effects in humans in a small trial by the authors, [48] can extend lifespan by 24% in mice when taken at old age. [49] [50]

See also

Related Research Articles

<span class="mw-page-title-main">Amino acid</span> Organic compounds containing amine and carboxylic groups

Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha amino acids appear in the genetic code.

<span class="mw-page-title-main">Phenylalanine</span> Type of α-amino acid

Phenylalanine is an essential α-amino acid with the formula C
9H
11NO
2. It can be viewed as a benzyl group substituted for the methyl group of alanine, or a phenyl group in place of a terminal hydrogen of alanine. This essential amino acid is classified as neutral, and nonpolar because of the inert and hydrophobic nature of the benzyl side chain. The L-isomer is used to biochemically form proteins coded for by DNA. Phenylalanine is a precursor for tyrosine, the monoamine neurotransmitters dopamine, norepinephrine (noradrenaline), and epinephrine (adrenaline), and the skin pigment melanin. It is encoded by the codons UUU and UUC.

Proline (symbol Pro or P) is an organic acid classed as a proteinogenic amino acid (used in the biosynthesis of proteins), although it does not contain the amino group -NH
2 but is rather a secondary amine. The secondary amine nitrogen is in the protonated form (NH2+) under biological conditions, while the carboxyl group is in the deprotonated −COO− form. The "side chain" from the α carbon connects to the nitrogen forming a pyrrolidine loop, classifying it as a aliphatic amino acid. It is non-essential in humans, meaning the body can synthesize it from the non-essential amino acid L-glutamate. It is encoded by all the codons starting with CC (CCU, CCC, CCA, and CCG).

<span class="mw-page-title-main">Glutamic acid</span> Amino acid and neurotransmitter

Glutamic acid is an α-amino acid that is used by almost all living beings in the biosynthesis of proteins. It is a non-essential nutrient for humans, meaning that the human body can synthesize enough for its use. It is also the most abundant excitatory neurotransmitter in the vertebrate nervous system. It serves as the precursor for the synthesis of the inhibitory gamma-aminobutyric acid (GABA) in GABA-ergic neurons.

Serine is an α-amino acid that is used in the biosynthesis of proteins. It contains an α-amino group, a carboxyl group, and a side chain consisting of a hydroxymethyl group, classifying it as a polar amino acid. It can be synthesized in the human body under normal physiological circumstances, making it a nonessential amino acid. It is encoded by the codons UCU, UCC, UCA, UCG, AGU and AGC.

<span class="mw-page-title-main">Cystine</span> Chemical compound

Cystine is the oxidized derivative of the amino acid cysteine and has the formula (SCH2CH(NH2)CO2H)2. It is a white solid that is poorly soluble in water. As a residue in proteins, cystine serves two functions: a site of redox reactions and a mechanical linkage that allows proteins to retain their three-dimensional structure.

<span class="mw-page-title-main">NMDA receptor</span> Glutamate receptor and ion channel protein found in nerve cells

The N-methyl-D-aspartatereceptor (also known as the NMDA receptor or NMDAR), is a glutamate receptor and ion channel found in neurons. The NMDA receptor is one of three types of ionotropic glutamate receptors, the other two being AMPA and kainate receptors. Depending on its subunit composition, its ligands are glutamate and glycine (or D-serine). However, the binding of the ligands is typically not sufficient to open the channel as it may be blocked by Mg2+ ions which are only removed when the neuron is sufficiently depolarized. Thus, the channel acts as a “coincidence detector” and only once both of these conditions are met, the channel opens and it allows positively charged ions (cations) to flow through the cell membrane. The NMDA receptor is thought to be very important for controlling synaptic plasticity and mediating learning and memory functions.

<span class="mw-page-title-main">Sarcosine</span> Chemical compound

Sarcosine, also known as N-methylglycine, or monomethylglycine, is a monopeptide with the formula CH3N(H)CH2CO2H. It exists at neutral pH as the zwitterion CH3N+(H)2CH2CO2−, which can be obtained as a white, water-soluble powder. Like some amino acids, sarcosine converts to a cation at low pH and an anion at high pH, with the respective formulas CH3N+(H)2CH2CO2H and CH3N(H)CH2CO2−. Sarcosine is a close relative of glycine, with a secondary amine in place of the primary amine.

Biosynthesis is a multi-step, enzyme-catalyzed process where substrates are converted into more complex products in living organisms. In biosynthesis, simple compounds are modified, converted into other compounds, or joined to form macromolecules. This process often consists of metabolic pathways. Some of these biosynthetic pathways are located within a single cellular organelle, while others involve enzymes that are located within multiple cellular organelles. Examples of these biosynthetic pathways include the production of lipid membrane components and nucleotides. Biosynthesis is usually synonymous with anabolism.

<span class="mw-page-title-main">Ligand-gated ion channel</span> Type of ion channel transmembrane protein

Ligand-gated ion channels (LICs, LGIC), also commonly referred to as ionotropic receptors, are a group of transmembrane ion-channel proteins which open to allow ions such as Na+, K+, Ca2+, and/or Cl− to pass through the membrane in response to the binding of a chemical messenger (i.e. a ligand), such as a neurotransmitter.

<span class="mw-page-title-main">Hippuric acid</span> Chemical compound

Hippuric acid is a carboxylic acid and organic compound. It is found in urine and is formed from the combination of benzoic acid and glycine. Levels of hippuric acid rise with the consumption of phenolic compounds. The phenols are first converted to benzoic acid, and then to hippuric acid and excreted in urine.

Glycolic acid (or hydroxyacetic acid; chemical formula HOCH2CO2H) is a colorless, odorless and hygroscopic crystalline solid, highly soluble in water. It is used in various skin-care products. Glycolic acid is widespread in nature. A glycolate (sometimes spelled "glycollate") is a salt or ester of glycolic acid.

<span class="mw-page-title-main">D-amino acid oxidase</span> Enzyme

D-amino acid oxidase is an enzyme with the function on a molecular level to oxidize D-amino acids to the corresponding α-keto acids, producing ammonia and hydrogen peroxide. This results in a number of physiological effects in various systems, most notably the brain. The enzyme is most active toward neutral D-amino acids, and not active toward acidic D-amino acids. One of its most important targets in mammals is D-Serine in the central nervous system. By targeting this and other D-amino acids in vertebrates, DAAO is important in detoxification. The role in microorganisms is slightly different, breaking down D-amino acids to generate energy.

<span class="mw-page-title-main">Collagen, type III, alpha 1</span>

Type III Collagen is a homotrimer, or a protein composed of three identical peptide chains (monomers), each called an alpha 1 chain of type III collagen. Formally, the monomers are called collagen type III, alpha-1 chain and in humans are encoded by the COL3A1 gene. Type III collagen is one of the fibrillar collagens whose proteins have a long, inflexible, triple-helical domain.

<span class="mw-page-title-main">NMDA receptor antagonist</span> Class of anesthetics

NMDA receptor antagonists are a class of drugs that work to antagonize, or inhibit the action of, the N-Methyl-D-aspartate receptor (NMDAR). They are commonly used as anesthetics for animals and humans; the state of anesthesia they induce is referred to as dissociative anesthesia.

<span class="mw-page-title-main">Serine hydroxymethyltransferase</span>

Serine hydroxymethyltransferase (SHMT) is a pyridoxal phosphate (PLP) (Vitamin B6) dependent enzyme (EC 2.1.2.1) which plays an important role in cellular one-carbon pathways by catalyzing the reversible, simultaneous conversions of L-serine to glycine and tetrahydrofolate (THF) to 5,10-Methylenetetrahydrofolate (5,10-CH2-THF). This reaction provides the largest part of the one-carbon units available to the cell.

<span class="mw-page-title-main">Erlenmeyer–Plöchl azlactone and amino-acid synthesis</span>

The Erlenmeyer–Plöchl azlactone and amino acid synthesis, named after Friedrich Gustav Carl Emil Erlenmeyer who partly discovered the reaction, is a series of chemical reactions which transform an N-acyl glycine to various other amino acids via an oxazolone.

<span class="mw-page-title-main">Glycine cleavage system</span>

The glycine cleavage system (GCS) is also known as the glycine decarboxylase complex or GDC. The system is a series of enzymes that are triggered in response to high concentrations of the amino acid glycine. The same set of enzymes is sometimes referred to as glycine synthase when it runs in the reverse direction to form glycine. The glycine cleavage system is composed of four proteins: the T-protein, P-protein, L-protein, and H-protein. They do not form a stable complex, so it is more appropriate to call it a "system" instead of a "complex". The H-protein is responsible for interacting with the three other proteins and acts as a shuttle for some of the intermediate products in glycine decarboxylation. In both animals and plants the glycine cleavage system is loosely attached to the inner membrane of the mitochondria. Mutations in this enzymatic system are linked with glycine encephalopathy.

Glycopeptides are peptides that contain carbohydrate moieties (glycans) covalently attached to the side chains of the amino acid residues that constitute the peptide.

O-linked glycosylation is the attachment of a sugar molecule to the oxygen atom of serine (Ser) or threonine (Thr) residues in a protein. O-glycosylation is a post-translational modification that occurs after the protein has been synthesised. In eukaryotes, it occurs in the endoplasmic reticulum, Golgi apparatus and occasionally in the cytoplasm; in prokaryotes, it occurs in the cytoplasm. Several different sugars can be added to the serine or threonine, and they affect the protein in different ways by changing protein stability and regulating protein activity. O-glycans, which are the sugars added to the serine or threonine, have numerous functions throughout the body, including trafficking of cells in the immune system, allowing recognition of foreign material, controlling cell metabolism and providing cartilage and tendon flexibility. Because of the many functions they have, changes in O-glycosylation are important in many diseases including cancer, diabetes and Alzheimer's. O-glycosylation occurs in all domains of life, including eukaryotes, archaea and a number of pathogenic bacteria including Burkholderia cenocepacia, Neisseria gonorrhoeae and Acinetobacter baumannii.

References

  1. ↑ The Merck Index: An Encyclopedia of Chemicals, Drugs, and Biologicals (11th ed.), Merck, 1989, ISBN   091191028X ,4386
  2. ↑ pubchem.ncbi.nlm.nih.gov/compound/750#section=IUPAC-Name&fullscreen=true
  3. ↑ Handbook of Chemistry and Physics, CRC Press, 59th edition, 1978
  4. ↑ "Solubilities and densities". Prowl.rockefeller.edu. Archived from the original on September 12, 2017. Retrieved November 13, 2013.
  5. ↑ Dawson, R.M.C., et al., Data for Biochemical Research, Oxford, Clarendon Press, 1959.
  6. ↑ "Nomenclature and Symbolism for Amino Acids and Peptides". IUPAC-IUB Joint Commission on Biochemical Nomenclature. 1983. Archived from the original on October 9, 2008. Retrieved March 5, 2018.
  7. ↑ "Glycine | Definition of glycine in English by Oxford Dictionaries". Archived from the original on January 29, 2018.
  8. ↑ Plimmer, R.H.A. (1912) [1908]. Plimmer, R.H.A.; Hopkins, F.G. (eds.). The chemical composition of the proteins. Monographs on biochemistry. Vol. Part I. Analysis (2nd ed.). London: Longmans, Green and Co. p. 82. Retrieved January 18, 2010.
  9. ↑ Braconnot, Henri (1820). "Sur la conversion des matières animales en nouvelles substances par le moyen de l'acide sulfurique" [On the conversion of animal materials into new substances by means of sulfuric acid]. Annales de Chimie et de Physique. 2nd series (in French). 13: 113–125. ; see p. 114.
  10. ↑ MacKenzie, Colin (1822). One Thousand Experiments in Chemistry: With Illustrations of Natural Phenomena; and Practical Observations on the Manufacturing and Chemical Processes at Present Pursued in the Successful Cultivation of the Useful Arts …. Sir R. Phillips and Company. p.  557.
  11. ↑ Boussingault (1838). "Sur la composition du sucre de gélatine et de l'acide nitro-saccharique de Braconnot" [On the composition of sugar of gelatine and of nitro-glucaric acid of Braconnot]. Comptes Rendus (in French). 7: 493–495.
  12. ↑ Horsford, E.N. (1847). "Glycocoll (gelatine sugar) and some of its products of decomposition". The American Journal of Science and Arts. 2nd series. 3: 369–381.
  13. ↑ Ihde, Aaron J. (1970). The Development of Modern Chemistry. Courier Corporation. ISBN   9780486642352.
  14. ↑ Berzelius, Jacob (1848). Jahres-Bericht über die Fortschritte der Chemie und Mineralogie (Annual Report on the Progress of Chemistry and Mineralogy). Vol. 47. Tübigen, (Germany): Laupp. p. 654. From p. 654: "Er hat dem Leimzucker als Basis den Namen Glycocoll gegeben. … Glycin genannt werden, und diesen Namen werde ich anwenden." (He [i.e., the American scientist Eben Norton Horsford, then a student of the German chemist Justus von Liebig] gave the name "glycocoll" to Leimzucker [sugar of gelatine], a base. This name is not euphonious and has besides the flaw that it clashes with the names of the rest of the bases. It is compounded from γλυχυς (sweet) and χολλα (animal glue). Since this organic base is the only [one] which tastes sweet, then it can much more briefly be named "glycine", and I will use this name.)
  15. ↑ Nye, Mary Jo (1999). Before Big Science: The Pursuit of Modern Chemistry and Physics, 1800-1940. Harvard University Press. ISBN   9780674063822.
  16. ↑ "glycine". Oxford Dictionaries. Archived from the original on November 13, 2014. Retrieved December 6, 2015.
  17. ↑ Cahours, A. (1858). "Recherches sur les acides amidés" [Investigations into aminated acids]. Comptes Rendus (in French). 46: 1044–1047.
  18. ↑ Okafor, Nduka (March 9, 2016). Modern Industrial Microbiology and Biotechnology. CRC Press. ISBN   9781439843239.
  19. ↑ Ingersoll, A. W.; Babcock, S. H. (1932). "Hippuric acid". Organic Syntheses . 12: 40.; Collective Volume, vol. 2, p. 328
  20. ↑ Wiley (December 14, 2007). Kirk-Othmer Food and Feed Technology, 2 Volume Set. John Wiley & Sons. ISBN   9780470174487.
  21. ↑ "Glycine Conference (prelim)". USITC. Archived from the original on February 22, 2012. Retrieved June 13, 2014.{{cite web}}: CS1 maint: bot: original URL status unknown (link)
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  23. ↑ Hart, J. Roger (2005). "Ethylenediaminetetraacetic Acid and Related Chelating Agents". Ullmann's Encyclopedia of Industrial Chemistry . Weinheim: Wiley-VCH. doi:10.1002/14356007.a10_095.
  24. ↑ Ingersoll, A. W.; Babcock, S. H. (1932). "Hippuric Acid". Org. Synth. 12: 40. doi:10.15227/orgsyn.012.0040.
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  48. ↑ Kumar, Premranjan; Liu, Chun; Hsu, Jean W.; Chacko, Shaji; Minard, Charles; Jahoor, Farook; Sekhar, Rajagopal V. (March 2021). "Glycine and N‐acetylcysteine (GlyNAC) supplementation in older adults improves glutathione deficiency, oxidative stress, mitochondrial dysfunction, inflammation, insulin resistance, endothelial dysfunction, genotoxicity, muscle strength, and cognition: Results of a pilot clinical trial". Clinical and Translational Medicine. 11 (3): e372. doi:10.1002/ctm2.372. ISSN   2001-1326. PMC   8002905 . PMID   33783984.
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