2-Mercaptoethanol

From Wikipedia, the free encyclopedia
Jump to: navigation, search
2-Mercaptoethanol
Skeletal formula of 2-mercaptoethanol Spacefill model of 2-mercaptoethanol
Identifiers
CAS number 60-24-2 YesY
PubChem 1567
ChemSpider 1512 YesY
EC number 200-464-6
UN number 2966
DrugBank DB03345
KEGG C00928 N
MeSH Mercaptoethanol
ChEBI CHEBI:41218 YesY
ChEMBL CHEMBL254951 YesY
RTECS number KL5600000
Beilstein Reference 773648
Gmelin Reference 1368
3DMet B00201
Jmol-3D images Image 1
Properties
Molecular formula C
2
H
6
SO
Molar mass 78.133 g mol−1
Density 1.114 g cm−3
Melting point −100 °C (−148 °F; 173 K)
Boiling point 157 °C; 314 °F; 430 K
log P -0.23
Vapor pressure 100 Pa (at 20 °C)
Acidity (pKa) 9.643
Basicity (pKb) 4.354
Refractive index (nD) 1.4996
Hazards
MSDS msds.chem.ox.ac.uk
GHS pictograms The corrosion pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The skull-and-crossbones pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS) The environment pictogram in the Globally Harmonized System of Classification and Labelling of Chemicals (GHS)
GHS signal word DANGER
GHS hazard statements H301, H310, H315, H317, H318, H330, H410
GHS precautionary statements P260, P273, P280, P284, P301+310, P302+350
EU classification Toxic T Dangerous for the Environment (Nature) N
R-phrases R20/22, R24, R34, R51/53
S-phrases S26, S36/37/39, S45, S61
Flash point 68 °C (154 °F; 341 K)
Explosive limits 18%
Related compounds
Related compounds Ethylene glycol

1,2-Ethanedithiol

Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 N (verify) (what is: YesY/N?)
Infobox references

2-Mercaptoethanol (also β-mercaptoethanol, BME, 2BME, 2-ME or β-met) is the chemical compound with the formula HOCH2CH2SH. ME or βME, as it is commonly abbreviated, is used to reduce disulfide bonds and can act as a biological antioxidant by scavenging hydroxyl radicals (amongst others). It is widely used because the hydroxyl group confers solubility in water and lowers the volatility. Due to its diminished vapor pressure, its odour, while unpleasant, is less objectionable than related thiols.

Preparation[edit]

2-Mercaptoethanol may be prepared by the action of hydrogen sulfide on ethylene oxide:[1]

Reaction scheme for the preparation of 2-mercaptoethanol from ethylene oxide and hydrogen sulfide

Reactions[edit]

2-Mercaptoethanol reacts with aldehydes and ketones to give the corresponding oxathiolanes. This makes 2-mercaptoethanol useful as a protecting group.[2]

Reaction scheme for the formation of oxathiolanes by reaction of 2-mercaptoethanol with aldehydes or ketones

Applications[edit]

Reducing proteins[edit]

Some proteins can be denatured by 2-mercaptoethanol via its ability to cleave disulfide bonds:

cysS-Scys + 2 HOCH2CH2SH → 2 cysSH + HOCH2CH2S-SCH2CH2OH
Reaction scheme for the cleavage of disulfide bonds by 2-mercaptoethanol

By breaking the S-S bonds, both the tertiary structure and the quaternary structure of some proteins can be disrupted.[3] 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 more generally 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.[4]

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.[5][6]

Preventing protein oxidation[edit]

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 used in several enzyme assays as a standard buffer.[7]

Denaturing ribonucleases[edit]

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.[8]

Safety[edit]

2-Mercaptoethanol is considered toxic, causing irritation to the nasal passageways and respiratory tract upon inhalation, irritation to the skin, vomiting and stomach pain through ingestion, and potentially death if severe exposure occurs. [9]

References[edit]

  1. ^ Knight, J. J. "2-Mercaptoethanol" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette) 2004, J. Wiley & Sons, New York. doi:10.1002/047084289.
  2. ^ "1,3-Dithiolanes, 1,3-Dithianes". Organic Chemistry Portal. Archived from the original on 17 May 2008. Retrieved 27 May 2008. 
  3. ^ "2-Mercaptoethanol". Chemicalland21.com. Archived from the original on 5 October 2006. Retrieved 8 October 2006. 
  4. ^ Aitken CE, Marshall RA, Puglisi JD (2008). "An oxygen scavenging system for improvement of dye stability in single-molecule fluorescence experiments". Biophys J 94 (5): 1826–35. doi:10.1529/biophysj.107.117689. PMC 2242739. PMID 17921203. 
  5. ^ Yeh, J. I. "Additives and microcalorimetric approaches for optimization of crystallization" in Protein Crystallization, 2nd Edition (Ed: T. Bergfors) 2009, International University Line, La Jolla, CA. ISBN 978-0-9720774-4-6.
  6. ^ Stevens R., Stevens L., Price N.C. (1983). "The Stabilities of Various Thiol Compounds used in Protein Purifications". Biochemical Education 11 (2): 70. doi:10.1016/0307-4412(83)90048-1. 
  7. ^ Verduyn, C., van Kleef, R., Frank, J., Schreuder, H., van Dijken, J.P. and Scheffers, W.A. (1985) Biochem. J. 226, 669-677.
  8. ^ Nelson, David R.; Lehninger, Albert L; Cox, Michael (2005). Lehninger principles of biochemistry. New York: W.H. Freeman. p. 148. ISBN 0-7167-4339-6. 
  9. ^ "Material Safety Data Sheet". JT Baker. Retrieved 31 July 2011.