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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 odor, while unpleasant, is less objectionable than related thiols.

Preparation

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

Reactions

2-Mercaptoethanol reacts with aldehydes and ketones to give the corresponding oxathiolanes. This makes 2-mercaptoethanol useful as a protecting group.^[3]

Applications

Reducing proteins

Some proteins can be denatured by 2-mercaptoethanol, which cleaves the disulfide bonds that may form between thiol groups of cysteine residues. In the case of excess 2-mercaptoethanol, the following equilibrium is shifted to the right:

RS–SR + 2 HOCH₂CH₂SH ⇌ HOCH₂CH₂S–SCH₂CH₂OH + 2 RSH

By breaking the S-S bonds, both the tertiary structure and the quaternary structure of some proteins can be disrupted.^[4] 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.^[5]

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.^[6]^[7]

Preventing protein oxidation

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.^[8]

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.^[9]

Safety

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.^[10]

References

^ ^a ^b 2-Mercaptoethanol
^ Knight, J. J. (2004) "2-Mercaptoethanol" in Encyclopedia of Reagents for Organic Synthesis (Ed: L. Paquette), J. Wiley & Sons, New York. doi:10.1002/047084289.
^ "1,3-Dithiolanes, 1,3-Dithianes". Organic Chemistry Portal. Archived from the original on 17 May 2008. Retrieved 27 May 2008.
^ "2-Mercaptoethanol". Chemicalland21.com. Archived from the original on 5 October 2006. Retrieved 8 October 2006.
^ 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.
^ Yeh, J. I. (2009) "Additives and microcalorimetric approaches for optimization of crystallization" in Protein Crystallization, 2nd Edition (Ed: T. Bergfors), International University Line, La Jolla, CA. ISBN 978-0-9720774-4-6.
^ 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.
^ Verduyn, C; Van Kleef, R; Frank, J; Schreuder, H; Van Dijken, J. P.; Scheffers, W. A. (1985). "Properties of the NAD(P)H-dependent xylose reductase from the xylose-fermenting yeast Pichia stipitis". The Biochemical Journal 226 (3): 669–77. doi:10.1042/bj2260669. PMC 1144764. PMID 3921014.
^ 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.
^ "Material Safety Data Sheet". JT Baker. Retrieved 31 July 2011.

English Journal

Water-soluble diiron hexacarbonyl complex as a CO-RM: controllable CO-releasing, releasing mechanism and biocompatibility.

Long L1, Jiang X, Wang X, Xiao Z, Liu X.
Dalton transactions (Cambridge, England : 2003).Dalton Trans.2013 Nov 28;42(44):15663-9. doi: 10.1039/c3dt51281a.
A water soluble diiron hexacarbonyl complex, [Fe2{μ-SCH2CH(OH)CH2(OH)}2(CO)6] (1), was synthesised by reacting thioglycol with Fe3(CO)12 in THF. This diiron complex was employed as carbon monoxide releasing molecule (CO-RM). The CO-releasing was initiated via substitution of the bound CO by cysteam
PMID 24045860

Charge transfer and blue shifting of vibrational frequencies in a hydrogen bond acceptor.

Wright AM1, Howard AA, Howard JC, Tschumper GS, Hammer NI.
The journal of physical chemistry. A.J Phys Chem A.2013 Jul 3;117(26):5435-46. doi: 10.1021/jp401642b. Epub 2013 May 24.
A comprehensive Raman spectroscopic/electronic structure study of hydrogen bonding by pyrimidine with eight different polar solvents is presented. Raman spectra of binary mixtures of pyrimidine with methanol and ethylene glycol are reported, and shifts in ν1, ν3, ν6a, ν6b, ν8a, ν8b, ν9a, ν15
PMID 23679020

Trace element determination by combining solid-phase microextraction hyphenated to elemental and molecular detection techniques.

Díez S1, Bayona JM.
Journal of chromatographic science.J Chromatogr Sci.2006 Aug;44(7):458-71.
The state of the art of analytical procedures based on solid-phase microextraction (SPME) and its applications to tin, mercury, arsenic, antimony, chromium, selenium, and lead determination in abiotic and biotic matrixes are critically reviewed from 1994 to present. First, sample pretreatment prior
PMID 16925944

Japanese Journal

Spreadability of Ovalbumin Monolayers at Air-water Interface. Effects of Additives to Spreading Solutions

Ishii Toshio,Muramatsu Mitsuo
Bulletin of the Chemical Society of Japan 44(3), 679-681, 1971
… The effect of additives (urea, potassium chloride, butanol, and thioglycol) to spreading solutions upon spread-ability of ovalbumin monolayers has been studied in terms of the rate constants and the limiting areas for intermediate (fast) and final (slow) processes of uncoiling of the protein molecule. …
NAID 130001976189

Studies on Metabolic Pathway of NAD in Yeast:Part III. Purification of Yeast 5'-Nucleotidase

TAKEI Shuzo
Agricultural and Biological Chemistry 31(8), 917-923, 1967
… Throughout purification steps, the ratio of the two activities were kept constant and they could not be separated even by treatments with EDTA, urea, thioglycol and alkaline buffer. …
NAID 130003522800

Studies on Tyrosinase in the Housefly:Part III. Activation of Protyrosinase by Natural Activator

INABA Takashi,FUNATSU Masaru
Agricultural and Biological Chemistry 28(4), 206-215, 1964
… Inhibition of the activation by various chemical reagents were studies and it was found that sodium picryl sulfate, N-bromosuccinimide or iodine inactivated natural activator irreversibly, and thioglycol or monoiodoacetate inhibited considerably. …
NAID 130003522200

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リンク元	「2-メルカプトエタノール」
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「2-メルカプトエタノール」

2-Mercaptoethanol
Names
	IUPAC name 2-Sulfanylethan-1-ol
	Other names 2-Hydroxy-1-ethanethiol; β-Mercaptoethanol; Thioglycol
Identifiers
CAS Number	60-24-2
3DMet	B00201
Beilstein Reference	773648
ChEBI	CHEBI:41218
ChEMBL	ChEMBL254951
ChemSpider	1512
DrugBank	DB03345
EC Number	200-464-6
Gmelin Reference	1368
Jmol 3D model	Interactive image
KEGG	C00928
MeSH	Mercaptoethanol
PubChem	1567
RTECS number	KL5600000
UN number	2966
	InChI InChI=1S/C2H6OS/c3-1-2-4/h3-4H,1-2H2 Key: DGVVWUTYPXICAM-UHFFFAOYSA-N ;
	SMILES OCCS ;
Properties
Chemical formula	C2H6OS
Molar mass	78.13 g·mol−1
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	100 Pa (at 20 °C)
Acidity (pKa)	9.643
Basicity (pKb)	4.354
Refractive index (nD)	1.4996
Hazards
Safety data sheet	msds.chem.ox.ac.uk
GHS pictograms
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 (DSD)	T 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%
	Lethal dose or concentration (LD, LC):
LD50 (Median dose)	244 mg/Kg (oral, rat); 150 mg/kg (skin, rabbit)
Related compounds
Related compounds	Ethylene glycol; 1,2-Ethanedithiol
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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	Infobox references