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| Targets |
L-Cysteine-3-13C targets the same molecular pathways as unlabeled L-Cysteine, including glutathione synthesis (as a substrate for glutamate-cysteine ligase and glutathione synthetase), hydrogen sulfide production (via cystathionine gamma-lyase and cystathionine beta-synthase), and protein biosynthesis. It also serves as a substrate for the transsulfuration pathway. Additionally, L-cysteine suppresses ghrelin and reduces appetite. As a tracer, the carbon-13 label at the alpha-carbon allows researchers to track the fate of cysteine-derived carbons in various metabolic pathways, including gluconeogenesis (via conversion to pyruvate) and the TCA cycle.
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| ln Vitro |
Drug compounds have included stable heavy isotopes of carbon, hydrogen, and other elements, mostly as quantitative tracers while the drugs were being developed. Because deuteration may have an effect on a drug's pharmacokinetics and metabolic properties, it is a cause for concern [1].
As a stable isotope tracer, L-Cysteine-3-13C is not used to measure biological activity in the traditional sense. Instead, it is added to cell culture media or administered to animals to incorporate 13C into downstream metabolites, including glutathione, H2S, taurine, pyruvate, and proteins. This allows for quantification of metabolic flux through the transsulfuration pathway, the cysteine catabolism pathway (cysteine dioxygenase pathway), and the oxidative stress response. L-Cysteine (unlabeled) has been shown to inhibit ghrelin secretion and reduce food intake in rodents and humans when administered exogenously. |
| ln Vivo |
In vivo, L-Cysteine-3-13C is administered to animals or humans to trace cysteine metabolism in real-time. It is used to assess the conversion of cysteine to glutathione (a major antioxidant), cysteine to pyruvate (via cysteine dioxygenase and cysteine sulfinate decarboxylase pathways), and cysteine to taurine and H2S. The 13C-labeled cysteine can be detected in blood, urine, and tissues after oral or intravenous administration, allowing for kinetic analysis of sulfur amino acid metabolism. Unlabeled L-Cysteine has been reported to suppress ghrelin and reduce appetite in humans. The labeled version is used to study the metabolic fate of cysteine in health and disease (e.g., in oxidative stress, inflammation, and metabolic disorders).
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| Enzyme Assay |
For non-cellular assays (analytical quantification), L-Cysteine-3-13C is prepared as a stock solution in 0.1 M HCl or water (1 mg/mL). For LC-MS/MS analysis, a calibration curve for L-Cysteine is prepared in human plasma or cell lysates (0.1-100 ug/mL) with a fixed concentration of L-Cysteine-3-13C (e.g., 10 ug/mL). Sample preparation: 50 uL plasma + 10 uL internal standard + 150 uL acetonitrile for protein precipitation. After centrifugation, the supernatant is diluted with water (1:1) and injected onto a C18 column with a mobile phase of 0.1% formic acid in water and acetonitrile (gradient elution). MRM transitions: L-Cysteine 122→76, L-Cysteine-3-13C 123→77. For enzyme activity assays (e.g., cystathionine gamma-lyase), the enzyme is incubated with L-Cysteine-3-13C (1-10 mM) in assay buffer, and 13C-labeled products (e.g., pyruvate-13C) are quantified by LC-MS.
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| Cell Assay |
For cell-based assays, hepatocytes (e.g., HepG2 cells), neuronal cells (e.g., SH-SY5Y), or cancer cells are seeded in 6-well plates (1×10⁶ cells/well) in DMEM with 10% FBS. For metabolic labeling, cells are cultured in medium lacking unlabeled cysteine and supplemented with L-Cysteine-3-13C (10-100 uM) for 6-48 hours. Cell lysates are prepared in 80% methanol containing internal standards. Protein pellets are hydrolyzed with 6 M HCl at 110degC for 24 hours for amino acid analysis. 13C enrichment in cysteine, glutathione, methionine, pyruvate, and TCA cycle intermediates is analyzed by LC-MS/MS or GC-MS. For protein synthesis studies (SILAC), cells are cultured in media containing L-Cysteine-3-13C for 5-7 population doublings, and proteins are analyzed by MS. For oxidative stress studies, cells are treated with H2O2 (100-500 uM) and glutathione levels are measured.
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| Animal Protocol |
For in vivo animal experiments, rats or mice are fasted overnight and then administered L-Cysteine-3-13C orally (gavage) at a dose of 10-100 mg/kg or intravenously at 5-50 mg/kg. Blood samples are collected at multiple time points (0, 15, 30, 60, 90, 120 minutes) from the tail vein. Plasma is separated, and proteins are precipitated with methanol. At the end of the experiment, tissues (liver, kidney, brain, skeletal muscle) are harvested and homogenized. L-Cysteine-3-13C and its metabolites (e.g., glutathione, taurine, pyruvate) are analyzed by LC-MS/MS. For protein turnover studies, animals receive repeated doses of labeled cysteine for 7-14 days, and tissue proteins are isolated, hydrolyzed, and analyzed by MS to determine the rate of protein synthesis. For ghrelin studies, plasma ghrelin levels are measured by ELISA after cysteine administration.
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| ADME/Pharmacokinetics |
L-Cysteine-3-13C has a molecular weight of 122.15, with a carbon-13 label at the alpha-carbon (C-3) providing a mass shift of +1 Da relative to unlabeled L-Cysteine (MW 121.16). The compound is a white crystalline powder with a melting point of approximately 240degC (dec.). It is soluble in water, dilute acids, and bases. The 13C label is stable and non-radioactive. It should be stored as a powder at -20degC, protected from light, to prevent oxidation of the thiol group. The compound is metabolically identical to unlabeled L-Cysteine, so its pharmacokinetics follow that of L-Cysteine: absorbed via amino acid transporters (e.g., ASCT2, EAAC1) and distributed to all tissues, with the liver being the primary site of metabolism.
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| Toxicity/Toxicokinetics |
L-Cysteine-3-13C is a stable isotope-labeled compound with the same low toxicity profile as natural L-Cysteine, an endogenous amino acid. At typical tracer doses (mg per sample or mg per kg body weight in animals), it poses no toxicity risk. L-Cysteine is generally recognized as safe (GRAS) as a dietary supplement and food additive. High doses may cause gastrointestinal discomfort (nausea, vomiting, diarrhea) and, in rare cases, neurotoxicity (due to excitotoxicity from cysteine-derived glutamate). However, at tracer doses, these effects are not observed. The compound is non-radioactive and considered safe for research use with standard handling precautions for amino acids.
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| References | |
| Additional Infomation |
L-Cysteine-3-13C is a research compound used as a stable isotope tracer, not an approved drug. It is not intended for therapeutic use and has not undergone clinical trials as a drug. Its primary applications are in metabolic research, including studying cysteine and glutathione metabolism, the transsulfuration pathway, H2S production, protein synthesis rates (SILAC), and the cysteine catabolism pathway. The compound is used to investigate disorders of sulfur amino acid metabolism (e.g., cystinuria, homocystinuria), oxidative stress, and redox biology. L-Cysteine-3-13C is also used as an internal standard for quantitative LC-MS analysis of L-Cysteine in biological and clinical samples. Available for research use only.
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| Molecular Formula |
C213CH7NO2S
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|---|---|
| Molecular Weight |
122.15
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| Exact Mass |
122.023
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| CAS # |
201612-57-9
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| Related CAS # |
L-Cysteine;52-90-4
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| PubChem CID |
101680328
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| Appearance |
White to off-white solid powder
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| LogP |
0.028
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| Hydrogen Bond Donor Count |
3
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| Hydrogen Bond Acceptor Count |
4
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| Rotatable Bond Count |
2
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| Heavy Atom Count |
7
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| Complexity |
75.3
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| Defined Atom Stereocenter Count |
1
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| SMILES |
[13CH2]([C@@H](C(=O)O)N)S
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| InChi Key |
XUJNEKJLAYXESH-IJGDANSWSA-N
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| InChi Code |
InChI=1S/C3H7NO2S/c4-2(1-7)3(5)6/h2,7H,1,4H2,(H,5,6)/t2-/m0/s1/i1+1
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| Chemical Name |
(2R)-2-amino-3-sulfanyl(313C)propanoic acid
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| HS Tariff Code |
2934.99.9001
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| Storage |
Powder -20°C 3 years 4°C 2 years In solvent -80°C 6 months -20°C 1 month |
| Shipping Condition |
Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)
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| Solubility (In Vitro) |
May dissolve in DMSO (in most cases), if not, try other solvents such as H2O, Ethanol, or DMF with a minute amount of products to avoid loss of samples
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| Solubility (In Vivo) |
Note: Listed below are some common formulations that may be used to formulate products with low water solubility (e.g. < 1 mg/mL), you may test these formulations using a minute amount of products to avoid loss of samples.
Injection Formulations
Injection Formulation 1: DMSO : Tween 80： Saline = 10 : 5 : 85 (i.e. 100 μL DMSO stock solution → 50 μL Tween 80 → 850 μL Saline)(e.g. IP/IV/IM/SC) *Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH ₂ O to obtain a clear solution. Injection Formulation 2: DMSO : PEG300 ：Tween 80 : Saline = 10 : 40 : 5 : 45 (i.e. 100 μL DMSO → 400 μLPEG300 → 50 μL Tween 80 → 450 μL Saline) Injection Formulation 3: DMSO : Corn oil = 10 : 90 (i.e. 100 μL DMSO → 900 μL Corn oil) Example: Take the Injection Formulation 3 (DMSO : Corn oil = 10 : 90) as an example, if 1 mL of 2.5 mg/mL working solution is to be prepared, you can take 100 μL 25 mg/mL DMSO stock solution and add to 900 μL corn oil, mix well to obtain a clear or suspension solution (2.5 mg/mL, ready for use in animals). View More
Injection Formulation 4: DMSO : 20% SBE-β-CD in saline = 10 : 90 [i.e. 100 μL DMSO → 900 μL (20% SBE-β-CD in saline)] Oral Formulations
Oral Formulation 1: Suspend in 0.5% CMC Na (carboxymethylcellulose sodium) Oral Formulation 2: Suspend in 0.5% Carboxymethyl cellulose Example: Take the Oral Formulation 1 (Suspend in 0.5% CMC Na) as an example, if 100 mL of 2.5 mg/mL working solution is to be prepared, you can first prepare 0.5% CMC Na solution by measuring 0.5 g CMC Na and dissolve it in 100 mL ddH2O to obtain a clear solution; then add 250 mg of the product to 100 mL 0.5% CMC Na solution, to make the suspension solution (2.5 mg/mL, ready for use in animals). View More
Oral Formulation 3: Dissolved in PEG400 (Please use freshly prepared in vivo formulations for optimal results.) |
| Preparing Stock Solutions | 1 mg | 5 mg | 10 mg | |
| 1 mM | 8.1867 mL | 40.9333 mL | 81.8666 mL | |
| 5 mM | 1.6373 mL | 8.1867 mL | 16.3733 mL | |
| 10 mM | 0.8187 mL | 4.0933 mL | 8.1867 mL |
*Note: Please select an appropriate solvent for the preparation of stock solution based on your experiment needs. For most products, DMSO can be used for preparing stock solutions (e.g. 5 mM, 10 mM, or 20 mM concentration); some products with high aqueous solubility may be dissolved in water directly. Solubility information is available at the above Solubility Data section. Once the stock solution is prepared, aliquot it to routine usage volumes and store at -20°C or -80°C. Avoid repeated freeze and thaw cycles.
Calculation results
Working concentration： mg/mL；
Method for preparing DMSO stock solution： mg drug pre-dissolved in μL DMSO (stock solution concentration mg/mL). Please contact us first if the concentration exceeds the DMSO solubility of the batch of drug.
Method for preparing in vivo formulation:：Take μL DMSO stock solution, next add μL PEG300, mix and clarify, next addμL Tween 80, mix and clarify, next add μL ddH2O，mix and clarify.
(1) Please be sure that the solution is clear before the addition of next solvent. Dissolution methods like vortex, ultrasound or warming and heat may be used to aid dissolving.
(2) Be sure to add the solvent(s) in order.
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