2-Mercaptoethanol
Chemical compound
From Wikipedia, the free encyclopedia
2-Mercaptoethanol is the organosulfur compound with the formula HOCH2CH2SH. It is a colorless liquid. ME or βME, as it is commonly abbreviated, is used to reduce disulfide bonds. It is widely used because the hydroxyl group confers solubility in water and lowers the volatility. Due to its diminished vapor pressure its rotten egg odor is less objectionable than related thiols.[3]
| |
 | |
| Names | |
|---|---|
| Preferred IUPAC name
2-Sulfanylethan-1-ol[1] | |
| Other names
2-Mercaptoethan-1-ol 2-Hydroxy-1-ethanethiol β-Mercaptoethanol Thioglycol Beta-merc, BME, 2BME, 2-ME, β-met | |
| Identifiers | |
3D model (JSmol) |
|
| 773648 | |
| ChEBI | |
| ChEMBL | |
| ChemSpider | |
| DrugBank | |
| ECHA InfoCard | 100.000.422 |
| EC Number |
|
| 1368 | |
| KEGG | |
| MeSH | Mercaptoethanol |
PubChem CID |
|
| RTECS number |
|
| UNII | |
| UN number | 2966 |
CompTox Dashboard (EPA) |
|
| |
| |
| Properties | |
| C2H6OS | |
| Molar mass | 78.13 g·mol−1 |
| Appearance | Colorless liquid[2] |
| Odor | Disagreeable, distinctive |
| Density | 1.114 g/cm3 |
| Melting point | −100 °C (−148 °F; 173 K) |
| Boiling point | 157 °C; 314 °F; 430 K |
| log P | −0.23 |
| Vapor pressure | 0.76 hPa (at 20 °C); 4.67 hPa (at 40 °C) |
| Acidity (pKa) | 9.643 |
| Basicity (pKb) | 4.354 |
Refractive index (nD) |
1.4996 |
| Hazards | |
| GHS labelling: | |
   | |
| Danger | |
| H301, H310, H315, H317, H318, H330, H410 | |
| P260, P273, P280, P284, P301+P310, P302+P350 | |
| Flash point | 68 °C (154 °F; 341 K) |
| Explosive limits | 18% |
| Lethal dose or concentration (LD, LC): | |
LD50 (median dose) |
244 mg/kg (oral, rat) |
| Related compounds | |
Related compounds |
|
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
| |
Production
2-Mercaptoethanol is manufactured industrially by the reaction of ethylene oxide with hydrogen sulfide. Thiodiglycol and various zeolites catalyze the reaction.[4]
Reactions
2-Mercaptoethanol cleaves disulfide bonds.
2-Mercaptoethanol reacts with aldehydes and ketones to give the corresponding oxathiolanes.[5] This makes 2-mercaptoethanol useful as a protecting group, giving a derivative whose stability is between that of a dioxolane and a dithiolane.[6]
Like most alkylthiols, it adds to Michael acceptors such as acrylonitrile.[7]
Applications
Reducing proteins
Some proteins are denatured by 2-mercaptoethanol. In the case of excess 2-mercaptoethanol, the following equilibrium is shifted to the right:
- RS–SR + 2 HOCH2CH2SH ⇌ 2 RSH + HOCH2CH2S–SCH2CH2OH
By breaking the S-S bonds, both the tertiary structure and the quaternary structure of some proteins can be disrupted.[8] Because of its ability to disrupt the structure of proteins, it was used in the analysis of proteins, for instance, to ensure that a protein solution contains monomeric protein molecules, instead of disulfide linked dimers or higher order oligomers. However, since 2-mercaptoethanol forms adducts with free cysteines and is somewhat more toxic, dithiothreitol (DTT) is generally more used especially in SDS-PAGE. DTT is also a more powerful reducing agent with a redox potential (at pH 7) of −0.33 V, compared to −0.26 V for 2-mercaptoethanol.[9]
2-Mercaptoethanol is often used interchangeably with dithiothreitol (DTT) or the odorless tris(2-carboxyethyl)phosphine (TCEP) in biological applications.
Although 2-mercaptoethanol has a higher volatility than DTT, it is more stable: 2-mercaptoethanol's half-life is more than 100 hours at pH 6.5 and 4 hours at pH 8.5; DTT's half-life is 40 hours at pH 6.5 and 1.5 hours at pH 8.5.[10][11]
2-Mercaptoethanol and related reducing agents (e.g., DTT) are often included in enzymatic reactions to inhibit the oxidation of free sulfhydryl residues, and hence maintain protein activity. It is often used in enzyme assays as a standard buffer component.[12]
Denaturing ribonucleases
2-Mercaptoethanol is used in some RNA isolation procedures to eliminate ribonuclease released during cell lysis. Numerous disulfide bonds make ribonucleases very stable enzymes, so 2-mercaptoethanol is used to reduce these disulfide bonds and irreversibly denature the proteins. This prevents them from digesting the RNA during its extraction procedure.[13]
Deprotecting carbamates
Some carbamate protecting groups such as carboxybenzyl (Cbz) or allyloxycarbonyl (alloc) can be deprotected using 2-mercaptoethanol in the presence of potassium phosphate in dimethylacetamide.[14]
Genetic transformation
DNA uptake in Escherichia coli can be facilitated by the addition of 2-mercaptoethanol in genetic transformation.[15]
Safety
See also
- Dithiothreitol (DTT)
- Dithiobutylamine (DTBA)
- TCEP