HEPES

Chembox new
Name = HEPES
ImageFile = HEPES.png ImageSize = 200px
ImageName = chemical structure of HEPES
IUPACName = 4-(2-hydroxyethyl)-1-
piperazineethanesulfonic acid
OtherNames = HEPES
Section1 = Chembox Identifiers
CASNo = 7365-45-9
RTECS = TY2900000
Section2 = Chembox Properties
Formula = C₈H₁₈N₂O₄S
MolarMass = 238.3012 g/mol
Appearance = white crystalline powder
Density = ? g/l, solid (25°C)
Solubility = 40 g/100 ml (20°C)
MeltingPt = >234-238°C (453-457K)
pKa = 3 and 7.55
Section7 = Chembox Hazards
ExternalMSDS = [http://www.sigmaaldrich.com/cgi-bin/hsrun/Suite7/Suite/HAHTpage/Suite.HsSigmaAdvancedSearch.formAction External MSDS]
MainHazards = Irritant.
NFPA-H = 2
NFPA-F =
NFPA-R =
FlashPt = Non-flammable.
RPhrases = R36, R37, R38.
SPhrases = S26, S36.

HEPES ("4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid") is a zwitterionic organic chemical buffering agent. HEPES is widely used in cell culture, largely because tests indicate it is better at maintaining physiological pH despite changes in carbon dioxide when compared to bicarbonate buffers.

The dissociation of water decreases with falling temperature, but the dissociation constants (pK) of phosphate and bicarbonate buffers do not change much with temperature. HEPES is like water in that dissociation decreases as the temperature decreases. This makes HEPES a preferred buffering agent for maintaining enzyme structure and function at low temperatures. [cite journal | author=Baicu SC, Taylor MJ. | title=Acid-base buffering in organ preservation solutions as a function of temperature: new parameters for comparing buffer capacity and efficiency | journal=Cryobiology | volume=45 | issue=1 | year=2002 | pages=33–48 | pmid=12445548 | doi=10.1016/S0011-2240(02)00104-9]

Lepe-Zuniga et al. reported a phototoxicity of HEPES when exposed to ambient light by the production of hydrogen peroxide. For best repeatability of results it is then strongly advised to keep any HEPES containing solution in darkness as much as possible.

Fears that HEPES may serve as a nutrient source for aerobic bacteria have been shown to be unfounded.Fact|date=August 2008

ee also

*CAPSO
*CHES
*MOPS
*HEPPS
*MES

References

* [http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2Y-476KX5C-27S&_coverDate=10%2F23%2F1987&_alid=325848278&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=4931&_sort=d&view=c&_acct=C000051263&_version=1&_urlVersion=0&_userid=3914355&md5=8ab3d9cb862ddc4ba9385e48d1e644ef Toxicity of light-exposed Hepes media.] Lepe-Zuniga JL, Zigler JS Jr, Gery I. Journal of Immunological Methods. 1987 Oct 23;103(1):145.
* [http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cmd=Retrieve&db=PubMed&list_uids=4019356&dopt=Abstract Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium.]
*Zigler JS Jr, Lepe-Zuniga JL, Vistica B, Gery I., In Vitro Cell Dev Biol. 1985 May;21(5):282-7.

External links