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L-プロリン
L-プロリン · プロリン · L(-)-プロリン · L-2-ピロリジンカルボン酸 · L(-)‐プロリン · L‐プロリン · L‐プロリン CRM6016‐A · L-プロリン-D7
識別子と物理属性
| CAS No. | 147-85-3 |
|---|---|
| 分子式 | C5H9NO2 |
| 平均分子量 | 115.13 g/mol |
| 単同位体質量 | 115.06332853 g/mol |
| SMILES | O=C(O)[C@@H]1CCCN1 |
| InChIKey | ONIBWKKTOPOVIA-BYPYZUCNSA-N |
| PubChem CID | 145742 |
| ChEMBL | CHEMBL54922 |
| ChEBI | CHEBI:17203 |
| EC No. | 205-702-2 |
| DTXSID | DTXSID5044021 |
| 現地名 | L-プロリン |
化学・物理的性質
| XLogP | -2.5 |
|---|---|
| 極性表面積 | 49.3 |
| 水素結合供与体数 | 2 |
| 水素結合受容体数 | 3 |
| 回転可能結合数 | 1 |
| 重原子数 | 8 |
| 形式電荷 | 0 |
| 複雑度 | 103 |
| 物質分類 | Biological Agents -> Amino Acids and Derivatives |
| 化粧品 | Cosmetic ingredients (Proline) -> CIR (Cosmetic Ingredient Review)Skin conditioningAntistaticHair conditioning |
| LogP（分配係数） | log Kow = -2.54 |
| 臭い | Odorless100.00%で。無臭 |
| 味 | Sweet |
| 食品添加物 | FLAVOR ENHANCER, FLAVORING AGENT OR ADJUVANT, NUTRIENT SUPPLEMENT -> FDA Substance added to food |
| 密度 | 1.064 at 24 °C1.35 |
| 香味料 | EU Flavoring substances |
| Color/Form | Flat needles from alcohol + etherprisms from waterWhite crystals or crystalline powder |
| 溶解度 | Solubility in 100 mL of water: 127 g at 0 °C162 g at 25 °C206.7 g at 50 °C239 g at 65 °CSolubility in alcohol: 1.55% at 35 °Cinsoluble in ether, butanol, isopropanolVery soluble in water, alcoholinsoluble in etherVery soluble in waterslightly soluble in ethanol, acetone, benzeneinsoluble in ether, propanol162.0 mg/mLH2O: 50 mg/mL溶ける |
| Decomposition | When heated to decomposition it emits toxic vapors of /nitrogen oxides/. |
| 融点 | 220-222 °C, decomposesMP: 215-220 °C with decomposition /D(+)-Proline/MP: 205 °C with decomposition /DL-Proline/221 °C228 °C (dec.) (lit.) |
| 比旋光度 | -85.5 º (c=4, H2O) |
| 沸点 | 215.41°C (rough estimate) |
| 蒸気圧 | 0Pa at 25℃ |
| FEMA | 3319 | L-PROLINE |
| 屈折率 | -85 ° (C=4, H2O) |
| 貯蔵条件 | 2-8°C |
| 外観・状態 | 粉 |
| pKa（酸解離定数） | 1.95, 10.64(at 25℃) |
| 色 | 白い |
| pH | 6.0-7.0 (25℃, 1M in H2O) |
| においのタイプ | 無臭 |
| 由来生物 | synthetic |
| JECFA Number | 1425 |
| Merck | 14,7780 |
| BRN | 80810 |
| 安定性 | 安定。強力な酸化剤とは相容れない。 |
| 化粧品成分の機能 | スキンコンディショニングヘアコンディショニング |
| InChI | 1S/C5H9NO2/c7-5(8)4-2-1-3-6-4/h4,6H,1-3H2,(H,7,8)/t4-/m0/s1 |
| InChIKey | ONIBWKKTOPOVIA-UHFFFAOYSA-N |
| SMILES | OC(=O)[C@@H]1CCCN1 |
| LogP（分配係数） | -2.54 at 20℃ |
| CAS データベース | 147-85-3(CAS DataBase Reference) |
| NISTの化学物質情報 | Proline(147-85-3) |
| EPAの化学物質情報 | L-Proline (147-85-3) |
化学的特性
L-Proline, an amino acid, is colorless to white crystal or crystalline powder that has a slight, characteristic odor with a slightly sweet taste. It is soluble in water, insoluble in ethanol, diethyl ether and n-butanol, yellow in case of hydrated ninhydrin test solution, glacial acetic acid Red after acidification; pH=6.3, decomposition point is 220-222°C; specific optical rotation [α]20D-85° (0.5-2.0mg/ml, H2O), [α]20D-60.4° (0.5-2.0mg /ml, 5mol/LHCl). It is synthesized from L-glutamine and L-glutamate via L-ornithine in intestine, and from L-ornithine in liver. It is widely used as an ingredient in infusion and infant formula.
安全性と法規制
| GHS 分類 | This chemical does not meet GHS hazard criteria for 99.1% (419 of 423) of all reports.Not ClassifiedAggregated GHS information provided per 423 reports by companies from 6 notifications to the ECHA C&L Inventory. |
|---|---|
| 規制情報 | Chemical: L-ProlineRegulation (EC) No 1831/2003 (amended)L-Proline is listed on the EPA's Chemical Data Reporting (CDR) system. Manufacturers and importers of L-Proline are required to report information about their production and use of this chemical to the EPA under the Toxic Substances Control Act (TSCA). (40 eCFR Part 711)Status: Active Update: 28-03-2023 https://echa.europa.eu/registration-dossier/-/registered-dossier/13104L-Proline: Does not have an individual approval but may be used under an appropriate group standard |
| その他の安全情報 | IMAP assessments - L-Proline: Environment tier I assessment |
| 有害性の概要 | Small increase in resorptions observed in intraperitoneal study of rats[REPROTOX] Safe when used as a flavoring agent in food[JECFA] May cause irritation[Sigma-Aldrich MSDS] |
| FDA 要件 | The food additive amino acids may be safely used as nutrients added to foods in accordance with the following conditions: (a) The food additive consists of one or more of the following individual amino acids in the free, hydrated, or anhydrous form, or as the hydrochloride, sodium, or potassium salts. L-Proline is included on this list. |
| Toxic Combustion Products | Special hazards arising from the substance or mixture: Carbon oxides, Nitrogen oxides |
| Hazard Classes and Categories | Not Classified |
| Hazardous Reactivities and Incompatibilities | Incompatible materials: Strong oxidizing agents |
| 消火手順 | Suitable extinguishing media: Use water spray, alcohol-resistant foam, dry chemical or carbon dioxide.Advice for firefighters: Wear self-contained breathing apparatus for firefighting if necessary. |
| 保管条件 | Keep container tightly closed in a dry and well-ventilated place. Storage class (TRGS 510): Non Combustible Solids. |
| 清掃方法 | ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Avoid dust formation. Avoid breathing vapors, mist or gas. Methods and materials for containment and cleaning up: Sweep up and shovel. Keep in suitable, closed containers for disposal. |
| 処分方法 | SRP: Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air qualitypotential migration in air, soil or watereffects on animal, aquatic and plant lifeand conformance with environmental and public health regulations. If it is possible or reasonable use an alternative chemical product with less inherent propensity for occupational harm/injury/toxicity or environmental contamination.Product: Offer surplus and non-recyclable solutions to a licensed disposal companyContaminated packaging: Dispose of as unused product. |
| Preventive Measures | ACCIDENTAL RELEASE MEASURES: Personal precautions, protective equipment and emergency procedures: Avoid dust formation. Avoid breathing vapors, mist or gas.Precautions for safe handling: Further processing of solid materials may result in the formation of combustible dusts. The potential for combustible dust formation should be taken into consideration before additional processing occurs. Provide appropriate exhaust ventilation at places where dust is formed.Appropriate engineering controls: General industrial hygiene practice.Gloves must be inspected prior to use. Use proper glove removal technique (without touching glove's outer surface) to avoid skin contact with this product. Dispose of contaminated gloves after use in accordance with applicable laws and good laboratory practices. Wash and dry hands.SRP: Local exhaust ventilation should be applied wherever there is an incidence of point source emissions or dispersion of regulated contaminants in the work area. Ventilation control of the contaminant as close to its point of generation is both the most economical and safest method to minimize personnel exposure to airborne contaminants. Ensure that the local ventilation moves the contaminant away from the worker. |
| Personal Protective Equipment (PPE) | Eye/face protection: Use equipment for eye protection tested and approved under appropriate government standards such as NIOSH (US) or EN 166(EU).Skin protection: Handle with gloves.Body Protection: Choose body protection in relation to its type, to the concentration and amount of dangerous substances, and to the specific work-place. The type of protective equipment must be selected according to the concentration and amount of the dangerous substance at the specific workplace.Respiratory protection: Respiratory protection is not required. Where protection from nuisance levels of dusts are desired, use type N95 (US) or type P1 (EN 143) dust masks. Use respirators and components tested and approved under appropriate government standards such as NIOSH (US) or CEN (EU). |
| 相互作用 | Proline plays an important role in plant response to various environmental stresses. However, its involvement in mitigation of heavy metal stress in plants remains elusive. In this study, we examined the effectiveness of exogenous proline (10 and 20 mM) in alleviating cadmium induced inhibitory effects in young olive plants (Olea europaea L. cv. Chemlali) exposed to two Cd levels (10 and 30 mg CdCl2/kg soil). The Cd treatment induced substantial accumulation of Cd in both root and leaf tissues and a decrease in gas exchange, photosynthetic pigments contents, uptake of essential elements (Ca, Mg and K) and plant biomass. Furthermore, an elevation of antioxidant enzymes activities (superoxide dismutase, catalase, glutathione peroxydase) and proline content in association with relatively high amounts of hydrogen peroxide, thiobarbituric acid reactive substances and electrolyte leakage were observed. Interestingly, the application of exogenous proline alleviated the oxidative damage induced by Cd accumulation. In fact, Cd-stressed olive plants treated with proline showed an increase of antioxidant enzymes activities, photosynthetic activity, nutritional status, plant growth and oil content of olive fruit. Generally, it seems that proline supplementation alleviated the deleterious effects of young olive plants exposed to Cd stress.The ability of exogenous compatible solutes, such as proline, to counteract cadmium (Cd) inhibitory effects in young date palm plants (Phoenix dactylifera L. cv Deglet Nour) was investigated. Two-year-old date palm plants were subjected for five months at different Cd stress levels (0, 10 and 30 mg CdCl2/kg soil) whether supplied or not with exogenous proline (20 mM) added through the irrigation water. Different levels of Cd stress altered plant growth, gas exchanges and chlorophyll content as well as water status, but at different extent among them. In contrast, an increase of antioxidant enzymes activities of Cd-treated plants in association with high amounts of proline content, hydrogen peroxide (H2O2), thiobarbituric acid reactive substances (TBARS) and electrolyte leakage (EL) were observed. Interestingly, exogenous proline mitigated the adverse effects of Cd on young date palm. Indeed, it alleviated the oxidative damage induced by Cd accumulation and established better levels of plant growth, water status and photosynthetic activity. Moreover, proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants.Hydroponic experiments were conducted to investigate an effect of exogenous application of proline (Pro25 uM) in alleviating arsenate (As(V)5 and 25 uM) toxicity in Solanum melongena L. (eggplant) seedlings. Exposure of As(V) declined growth of eggplant, which was coincided with an enhanced accumulation of As. However, exogenous Pro application alleviated As(V) toxicity in eggplant seedlings by reducing the accumulation of As. The fluorescence characteristics (JIP-test): phiP0, psi0, phiE0, PIABS, ABS/RC, TR0/RC, ET0/RC, DI0/RC, NPQ and qP were also affected by As(V). However, the effects of As(V) were more prominent on PIABS DI0/RC and NPQ. In Pro treated seedlings, following parameters viz. phiP0, psi0, phiE0 and PIABS were stimulated, while, energy flux parameters (ABS/RC, TR0/RC, ET0/RC and DI0/RC) were inhibited. Toxic effects of As(V) on photochemistry of photosystem II (PS II) were ameliorated by an exogenous application of Pro. Oxidative stress markers: superoxide radical, hydrogen peroxide and malondialdehyde (lipid peroxidation) were enhanced by As(V) exposure, however, their levels were significantly diminished by an exogenous application of Pro. Treatment of As(V) stimulated the activities of superoxide dismutase, peroxidase and catalase except that of glutathione-S-transferase. Exogenous Pro application improved the activities of enzymatic antioxidants. The level of endogenous Pro was higher in As(V) treated as well as in Pro fed seedlings. The activity of a key enzyme of Pro biosynthesis: delta(1)-pyrroline-5-carboxylate synthetase was higher in Pro fed seedlings. The activity of Pro dehydrogenase was inhibited under As(V) stress, and its activity was minimum in case of Pro+As(V) combination. These results indicate that Pro metabolism could play a key role in regulating the accumulation of As and levels of antioxidants, which concomitantly result into a better growth of eggplant seedlings when compared to the As(V) treatments alone.This study was aimed to evaluate protective and therapeutic effects of a specific mixture, containing vitamin C, lysine, proline, epigallocatechin gallate and zinc, as well as alpha-1-antitrypsin protein on lung tumorigenesis induced by benzo(a) pyrene [B(a)P] in mice. Swiss albino mice were divided into two main experiments, experiment (1) the mice were injected with 100 mg/kg B(a)P and lasted for 28 weeks, while experiment (2) the mice were injected with 8 doses each of 50 mg/kg B(a)P and lasted for 16 weeks. Each experiment (1 and 2) divided into five groups, group (I) received vehicle, group (II) received the protector mixture, group (III) received the carcinogen B(a)P, group (IV) received the protector together with the carcinogen (simultaneously) and group (V) received the carcinogen then the protector (consecutively). Total sialic acid, thiobarbituric acid reactive substances, vascular epithelial growth factor, hydroxyproline levels, as well as elastase and gelatinase activities showed significant elevation in group (III) in the two experiments comparing to control group (P < 0.001). These biochemical alterations were associated with histopathological changes. Administration of the protector in group IV and group V causes significant decrease in such parameters with improvement in histopathological alterations with improvement in histopathological alterations when compared with group III in the two experiments (P < 0.001). The present protector mixture has the ability to suppress neoplastic alteration and restore the biochemical and histopathological parameters towards normal on lung carcinogenesis induced by benzo(a) pyrene in mice. Furthermore, the present mixture have more protective rather than therapeutic action.For more Interactions (Complete) data for (L)-PROLINE (8 total), please visit the HSDB record page. |
| 健康影響 | Chronically high levels of proline are associated with at least 5 inborn errors of metabolism including: Hyperprolinemia Type I, Hyperprolinemia Type II, Iminoglycinuria, Prolinemia Type II and Pyruvate carboxylase deficiency. |
| 環境中動態 | TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 3.4(SRC), determined from a structure estimation method(2), indicates that (L)-proline is expected to have very high mobility in soil(SRC). The pKa values of (L)-proline are 1.99 and 10.60(3), indicating that this compound will exist as a zwitterion in the environment and zwitterions generally adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). Volatilization from moist soil is not expected because the compound exists as an ion and ions do not volatilize. (L)-Proline is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 3.0X10-8 mm Hg at 25 °C(SRC), determined from a fragment constant method(2). Using aquatic screening tests, 100% biodegradation of (L)-proline was reported(5), suggesting that biodegradation is an important environmental fate process in soil(SRC).AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 3.4(SRC), determined from a structure estimation method(2), indicates that (L)-proline is not expected to adsorb to suspended solids and sediment(SRC). The pKa values of (L)-proline are 1.99 and 10.60(3), indicating that this compound will exist as a zwitterion at pH values of 5 to 9therefore, volatilization from water surfaces is not expected to be an important fate process. According to a classification scheme(4), an estimated BCF of 3(SRC), from its log Kow of -2.54(5) and a regression-derived equation(2), suggests the potential for bioconcentration in aquatic organisms is low(SRC). Using aquatic screening tests, 100% biodegradation of (L)-proline was reported(6), suggesting that biodegradation is an important environmental fate process in water(SRC).ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), (L)-proline, which has an estimated vapor pressure of 3.02X10-8 mm Hg at 25 °C(SRC), determined from a fragment constant method(2), is expected to exist solely in the particulate phase in the ambient atmosphere. Particulate-phase (L)-proline may be removed from the air by wet and dry deposition(SRC).(L)-Proline does not contain chromophores that absorb at wavelengths >290 nm(4) and, therefore, is not expected to be susceptible to direct photolysis by sunlight(SRC). |
| 毒性の概要 | Safe in the present practices of use and concentration. Ingredient, concentration, and use information are available in documents discoverable at https://cir-reports.cir-safety.orgIDENTIFICATION AND USE: L-Proline is a solid. It is used in biochemical and nutritional research, microbiological tests, culture media, as a laboratory reagent, and dietary supplement. It is also used in pharmaceutical preparations for injection or infusion. HUMAN EXPOSURE AND TOXICITY: There are no data available. ANIMAL STUDIES: In a 30-day study, a group of seven female rats were given L-proline at a dose of 50 mg/kg bw per day in water. A group of 10 rats served as the control group. After 30 days, all animals were weighed, necropsied, and subjected to a complete gross examination. Histopathology and microscopic examinations of the liver and kidneys were conducted. Samples of serum were obtained for determination of enzyme activities, and concentrations of creatinine and total protein. There were no treatment-related effects in rats given L-proline at 50 mg/ kg bw per day compared with the controls. Of 20 common amino acids only proline enhanced formation of mutagenic activity measured in S typhimurium TA98 with rat liver microsomes. In the assay for reverse mutation in Salmonella typhimurium, negative results were reported for L-proline at concentrations of up to 1000 mg/mL, with and without metabolic activation, in several strains of S. typhimurium (TA92, TA97, TA98, TA100, TA102, TA1530, TA1531, TA1532, TA1535, TA1537, TA1538, and TA1964). ECOTOXICITY STUDIES: Proline-treated plants showed high antioxidant enzymes activities (superoxide dismutase, catalase and glutathione peroxydase) in roots and leaves as compared to Cd-treated plants. Proline plays an important role in plant response to various environmental stresses. For example, proline supplementation alleviated the deleterious effects of young olive plants exposed to Cd stress.Glycogenic, by L-Proline oxidase in the kidney, it is ring-opened and is oxidized to form L-Glutamic acid. L-Ornithine and L-Glutamic acid are converted to L-Proline via L-Glutamic acid-gamma-semialdehyde. It is contained abundantly in collagen, and is intimately involved in the function of arthrosis and chordae. |
| Plant Concentrations | Proline has been identified in over 200 plants(1). /Proline/[Table#2998] |
| Soil Adsorption/Mobility | Using a structure estimation method based on molecular connectivity indices(1), the Koc of (L)-proline can be estimated to be 3.41(SRC). According to a classification scheme(2), this estimated Koc value suggests that (L)-proline is expected to have very high mobility in soil. The pKa values of (L)-proline are 1.99 and 10.60(3), indicating that this compound will exist as a zwitterion in the environment and zwitterions generally adsorb more strongly to soils containing organic carbon and clay than their neutral counterparts(4). |
| Natural Pollution Sources | (L)-Proline is a non-essential amino acid for human development. It is the only imino acid of the 20 amino acids commonly found in proteins(1). (L)-Proline occurs in over 200 plants(2). |
| Artificial Pollution Sources | (L)-Proline's production and use in parenteral nutrition(1), as a dietary supplement(1), food additive(2) and as a starting material for pharmaceutical manufacture(1) may result in its release to the environment through various waste streams(SRC). |
| Environmental Biodegradation | AEROBIC: (L)-Proline was determined to be readily biodegradable in water based on 100% biodegradation using screening tests(1).PURE CULTURE: Pseudomonas, Dithiobacter, Enterobacter and some species of Bacillus, which are able to use methylamine as a sole nitrogen source but not as a sole carbon source, were able to use (L)-proline as both a carbon and energy source(1). |
| Carcinogen Classification | No indication of carcinogenicity to humans (not listed by IARC). |
| Environmental Bioconcentration | An estimated BCF of 3 was calculated in fish for (L)-proline(SRC), using a log Kow of -2.54(1) and a regression-derived equation(1). According to a classification scheme(2), this BCF suggests the potential for bioconcentration in aquatic organisms is low(SRC). |
| Volatilization from Water/Soil | The pKa values of (L)-proline are 1.99 and 10.60(1), indicating that this compound will exist as a zwitterion at pH values of 5 to 9therefore, volatilization from water surfaces is not expected to be an important fate process. (L)-Proline is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 3.0X10-8 mm Hg(SRC), determined from a fragment constant method(2). |
| F | 3-10 |
| 水環境危害等級（WGK） | 3 |
| TSCA 収載状態 | TSCA listed |
| RTECS 番号 | TW3584000 |
| 毒性 | LD50 orally in Rabbit: > 5110 mg/kg |
| 税関コード | 29339990 |
| 危険文句（R） | 36/37/38-22 |
| 化審法 | (9)-1626 届出不要化学物質 |
| 危険表示 | Xi,Xn |
| 安全措置（S） | 24/25-36/37/39-26 |
| 貯蔵分類 | 13 - Non Combustible Solids |
| 有害物質データ | 147-85-3(Hazardous Substances Data) |
用途
解説
L-プロリン，プロリン，(S)-pyrrolidine-2-carboxylic acid．C5H9NO2(115.13)．略号ProまたはP．非必須アミノ酸．タンパク質構成アミノ酸として，また遊離の状態で広く分布している．タンパク質中では，ペプチド鎖の折れ曲がる位置に存在し，特殊な立体構造の保持に役立っている．ゼラチン，ツェイン，グリアジンなどの加水分解物からロダニル酸塩，ライネッケ塩を用いる沈殿法や，亜硝酸を作用させ，α-アミノ酸を分解する方法，あるいは発酵法で製造する．生体内ではグルタミン酸から合成される．L-プロリンは針状晶．分解点220～222 ℃．[α]20D－52.6°(0.5 mol L－1 塩酸)．pK1 1.99，pK2 10.60，pI6.30．水，エタノールに易溶，エーテル，クロロホルムに不溶．γ-ヒドロキシ-，γ-メチル-，γ-メチル-γ-ヒドロキシプロリン類やプロリンベタインもコラーゲンや植物中に見いだされている．弱い甘味がある．
天然物の起源
Reported found as a component in many proteins; also widely occurring as the free acid in natural products. A major constituent of collagen, the main fibrous protein found in bone, cartilage and other connective tissue.
使用
L-Proline is an amino acid and precursor (with vitamin C) for collagen, the building block of the structure of tendons, ligaments, arteries, veins and muscles. It is important in wound healing.
一般的な説明
L-Proline is a non-essential amino acid, which is a building block of proteins. Peptides bond to proline, making it a useful building block for proteins. It can be used as a cell culture media component for the commercial biomanufacturing of therapeutic recombinant proteins and monoclonal antibodies. L-Proline plays important roles in various biological processes. It is involved in the synthesis of collagen, which is one of the most abundant proteins in the human body and provides structural support to tissues such as skin, bone, cartilage, and tendons.
製法・合成法
製造方法
Synthesis of L-proline: Using glutamic acid as a raw material, it is esterified with absolute ethanol under the catalysis of sulfuric acid, and triethanolamine is added to free the aminosulfate to obtain glutamic acid-δ-ethyl ester. The glutamic acid-δ-ethyl ester is then reduced with a metal reducing agent potassium borohydride to obtain crude proline, which is finally separated and purified to obtain crude L-proline.
純化方法
A likely impurity is hydroxyproline. Purify L-proline via its picrate which is crystallised twice from water, then decomposed with 40% H2SO4. The picric acid is extracted with diethyl ether, the H2SO4 in solution is precipitated with Ba(OH)2, and the filtrate is evaporated. The residue is crystallised from hot absolute EtOH [Mellan & Hoover J Am Chem Soc 73 3879 1951] or EtOH/Et2O. Its solubility in H2O is >100%. It sublimes at 182-187o/0.3mm with 99.4% recovery and unracemised [Gross & Gradsky J Am Chem Soc 77 1678 1955]. It is hygroscopic and is stored in a desiccator. [Greenstein & Winitz The Chemistry of the Amino Acids J. Wiley, Vol 3 pp 2178-2199 1961, Beilstein 22 III/IV 8, 22/1 V 31.]