2-Thiouracil (2TU): Properties, Uses & Lab Handling Guide

2-Thiouracil(2TU) is a sulfur-substituted pyrimidine nucleobase analog in which the carbonyl oxygen at the 2-position of uracil is replaced by a sulfur atom, conferring unique solubility characteristics and broad utility in RNA metabolism research, transcription studies, and thyroid-related biochemical investigations.

Chemical Name

2-Thiouracil (2-sulfanylidene-1H-pyrimidin-4(3H)-one)

Abbreviation

2TU

Water Solubility

0.5 g/L; soluble in alkaline solution

Molecular Formula

C₄H₄N₂OS

Molecular Weight

128.15 g/mol

Primary Application

RNA metabolic labeling, transcription research, thyroid biochemistry

Storage Recommendation

Store in a cool, dry, well-ventilated area away from light

Chemical Identity and Physical Properties

2-Thiouracil (2TU) is a naturally occurring and synthetically accessible pyrimidine analog with the molecular formula C₄H₄N₂OS and a molecular weight of approximately 128.15 g/mol. Structurally, it differs from uracil solely by the replacement of the C2 carbonyl oxygen with a sulfur atom, producing a thioamide moiety that significantly alters its hydrogen-bonding capacity and electronic properties.

In terms of solubility, 2TU has a water solubility of 0.5 g/L at ambient temperature. Its solubility increases markedly in alkaline aqueous solutions, where deprotonation of the thiol tautomer promotes ionization and dissolution. This pH-dependent solubility is an important practical consideration when preparing stock solutions for cell culture or biochemical assays. Researchers are advised to prepare alkaline stock solutions (e.g., in dilute NaOH or phosphate-buffered saline adjusted to pH 8–9) and then dilute into the working medium to achieve the desired final concentration.

2TU exhibits characteristic UV absorption due to the extended conjugation introduced by the thio substitution, which can be exploited for concentration determination by spectrophotometry. Solid 2TU is typically a white to pale-yellow crystalline powder.

Biological Roles and Research Applications

2-Thiouracil occupies an important niche in several areas of modern biochemical and molecular biology research. Its applications span RNA metabolic labeling, thyroid biology, and the study of pyrimidine biosynthesis pathways.

RNA Metabolic Labeling: Because 2TU can be incorporated into newly synthesized RNA in place of uracil by cellular RNA polymerases, it is widely used as a metabolic label to track de novo RNA synthesis. Once incorporated, thio-modified RNA can be selectively isolated using thiol-reactive chemistry (e.g., biotinylation followed by streptavidin pulldown), enabling researchers to separate newly transcribed RNA from the pre-existing RNA pool. This approach is foundational to techniques such as SLAM-seq (thiol-linked alkylation for the metabolic sequencing of RNA), which maps transcriptome-wide RNA dynamics at single-nucleotide resolution.

Thyroid Research: 2TU and related thiouracil compounds have a well-established history as antithyroid agents. They inhibit thyroid peroxidase, thereby blocking the iodination of tyrosine residues in thyroglobulin and reducing thyroid hormone synthesis. Experimental models employing 2TU to induce hypothyroidism in rodents have been used extensively to study thyroid physiology and to evaluate novel therapeutics.

Biochemical Tool: As a pyrimidine analog, 2TU is also employed as a research tool to dissect nucleotide biosynthesis, to study nucleobase transport mechanisms, and as a reference standard in analytical chemistry workflows.

Preparation of Working Solutions

Given the limited aqueous solubility of 2TU (0.5 g/L in water), careful preparation of stock and working solutions is essential to ensure experimental reproducibility.

Alkaline Stock Solution: Dissolve 2TU in a minimum volume of dilute NaOH (0.1 M) or in phosphate-buffered saline (PBS) adjusted to pH 8.5–9.0. This exploits the enhanced solubility of the ionized thiolate form. Typical stock concentrations range from 10 mM to 100 mM depending on experimental requirements. Filter-sterilize the stock solution through a 0.22 µm membrane if use in cell culture is intended.

Dilution into Working Medium: Add the alkaline stock dropwise to the culture medium or reaction buffer with gentle mixing, verifying that the final pH remains within the physiological or assay-compatible range. Avoid prolonged exposure to strongly oxidizing conditions, as the thio group is susceptible to oxidation.

DMSO Solutions: For applications where aqueous solubility is insufficient, 2TU may also be dissolved in DMSO to prepare concentrated stocks. Ensure that the final DMSO concentration in working solutions does not exceed levels tolerated by the biological system under study (typically ≤0.1% v/v for cell-based assays).

Storage of Solutions: Prepared stock solutions should be aliquoted, protected from light, and stored at −20 °C to minimize oxidative degradation. Avoid repeated freeze-thaw cycles.

Safety, Handling and Storage

2-Thiouracil should be handled with standard laboratory precautions appropriate for a potentially hazardous organic compound. Researchers should consult the current Safety Data Sheet (SDS) supplied by Aladdin Scientific before use.

Personal Protective Equipment (PPE): Wear appropriate laboratory gloves (nitrile recommended), safety glasses or goggles, and a laboratory coat when handling solid or dissolved 2TU. If dust generation is anticipated during weighing, use a certified fume hood and consider respiratory protection.

Hazard Considerations: 2TU has antithyroid activity and may pose an endocrine-disruption risk upon repeated or significant exposure. Minimize inhalation and skin contact. Avoid ingestion. Pregnant or breastfeeding individuals should take particular care and consult institutional safety officers before handling.

Solid Storage: Store the bulk solid in a tightly sealed container in a cool (15–25 °C), dry, well-ventilated location, protected from light and moisture. Keep away from strong oxidizing agents and strong bases in concentrated form.

Disposal: Dispose of 2TU and solutions containing 2TU in accordance with local, institutional and national regulations governing organic chemical waste. Do not pour down the drain without verifying local permissibility.

Quality, Specifications and Ordering

Aladdin Scientific's 2-Thiouracil (SKU: T106704) is supplied as a high-purity research-grade reagent suitable for use in molecular biology, biochemistry and cell biology applications. Researchers should verify the current certificate of analysis (CoA) for lot-specific purity data prior to experimental use.

Specification Highlights:

• Water solubility: 0.5 g/L; soluble in alkaline solution
• Molecular formula: C₄H₄N₂OS
• Molecular weight: ~128.15 g/mol
• Appearance: White to pale-yellow crystalline powder (typical; verify CoA)

Ordering: T106704 is available through Aladdin Scientific's online platform or via your institutional procurement team. For bulk quantities, custom pack sizes, or institutional pricing, contact Aladdin Scientific's sales team directly. Ensure that your institution's import and regulatory requirements for thiouracil-class compounds are satisfied prior to ordering.

Returns and Quality Issues: If a product does not meet the stated specifications, contact Aladdin Scientific customer service with the lot number and CoA for resolution in accordance with the company's returns and refund policy.

Frequently asked questions

What is the best solvent to dissolve 2-Thiouracil for cell culture experiments?

2-Thiouracil has limited water solubility (0.5 g/L), so it is best dissolved in a dilute alkaline solution such as 0.1 M NaOH or PBS adjusted to pH 8.5–9.0 to prepare a concentrated stock. This stock is then diluted into cell culture medium to achieve the desired working concentration while maintaining physiological pH. DMSO can also be used for initial dissolution if aqueous alkaline conditions are not compatible with the downstream application.

How does 2-Thiouracil enable RNA metabolic labeling?

When supplied to cells, 2TU is incorporated into newly transcribed RNA in place of uracil by cellular RNA polymerases. The resulting thio-modified RNA can then be selectively captured using thiol-reactive chemistry, such as biotinylation with iodoacetamide-biotin followed by streptavidin-based purification. This allows researchers to isolate and analyze only newly synthesized RNA, providing a snapshot of active transcription under specific experimental conditions.

What safety precautions should be taken when handling 2-Thiouracil?

Researchers should wear nitrile gloves, safety glasses and a laboratory coat when handling 2TU in solid or solution form. Because 2TU possesses antithyroid activity, repeated or significant dermal or inhalation exposure should be avoided. Solid 2TU should be weighed in a fume hood to prevent dust inhalation. Always consult the current SDS from Aladdin Scientific before use, and follow your institution's chemical waste disposal regulations when discarding 2TU or solutions containing it.

Can 2-Thiouracil solutions be stored long-term, and how should they be stored?

Prepared 2TU solutions should be aliquoted into single-use volumes, protected from light and stored at −20 °C to minimize oxidative degradation of the thio group. Avoid repeated freeze-thaw cycles, which can accelerate decomposition. Solid bulk material should be stored in a sealed container at 15–25 °C in a cool, dry, well-ventilated area away from light and strong oxidizing agents.

References

1. Schwalb B, et al. TT-seq maps the human transient transcriptome. Science. 2016;352(6290):1225-1228. doi:10.1126/science.aad9841
2. Muhar M, et al. SLAM-seq defines direct gene-regulatory functions of the BRD4-MYC axis. Science. 2018;360(6390):800-805. doi:10.1126/science.aao2793
3. Astwood EB. The chemical nature of compounds which inhibit the function of the thyroid gland. J Pharmacol Exp Ther. 1943;78(1):79-89.
4. Aladdin Scientific. 2-Thiouracil (2TU), SKU T106704 — Product Information and Safety Data Sheet. Aladdin Scientific; accessed 2024.

Products are supplied for research and development use only. Not for use in humans, animals, diagnosis, or therapy.