Editing HEPES

{{chembox
| Verifiedfields = changed
| Watchedfields = changed
| verifiedrevid = 448969371
| Name = HEPES
| ImageFile = HEPES.png
| ImageName = chemical structure of HEPES
| ImageClass   = skin-invert
| PIN = 2-[4-(2-Hydroxyethyl)piperazin-1-yl]ethane-1-sulfonic acid
| OtherNames = HEPES
|Section1={{Chembox Identifiers
| ChemSpiderID_Ref = {{chemspidercite|correct|chemspider}}
| ChemSpiderID = 22278
| UNII_Ref = {{fdacite|correct|FDA}}
| UNII = RWW266YE9I
| InChI = 1/C8H18N2O4S/c11-7-5-9-1-3-10(4-2-9)6-8-15(12,13)14/h11H,1-8H2,(H,12,13,14)
| InChIKey = JKMHFZQWWAIEOD-UHFFFAOYAC
| StdInChI_Ref = {{stdinchicite|correct|chemspider}}
| StdInChI = 1S/C8H18N2O4S/c11-7-5-9-1-3-10(4-2-9)6-8-15(12,13)14/h11H,1-8H2,(H,12,13,14)
| StdInChIKey_Ref = {{stdinchicite|correct|chemspider}}
| StdInChIKey = JKMHFZQWWAIEOD-UHFFFAOYSA-N
| CASNo_Ref = {{cascite|correct|CAS}}
| CASNo = 7365-45-9
| CASNo_Comment = (free acid)
| CASNo2_Ref = {{cascite|unknown|CAS}}
| CASNo2 = 75277-39-3
| CASNo2_Comment = (sodium salt)
| RTECS = TL6809000
| EINECS = 230-907-9
| Beilstein = 883043
| ChEBI_Ref = {{ebicite|correct|EBI}}
| ChEBI = 42334
| SMILES = OCCN1CC[NH+](CCS(=O)([O-])=O)CC1
| PubChem = 23831
}}
|Section2={{Chembox Properties
| C=8 | H=18 | N=2 | O=4 | S=1
| MolarMass = 238.3012 g/mol
| Appearance = white crystalline powder
| Density = Not applicable
| Solubility = 40 g/100 ml (20°C)
| MeltingPt = >234-238°C (453-457K)
| pKa = 3 (p''K''<sub>a1</sub>),<br> 7.5 (p''K''<sub>a2</sub>)<ref>{{cite journal |vauthors = Johnson MA, Seifert S, Petrache HI, Kimble-Hill AC |date= 2014|title= Phase Coexistence in Single-Lipid Membranes Induced by Buffering Agents|journal= Langmuir|volume= 30|issue= 33|pages= 9880-9885|doi= 10.1021/la5018938 |pmc=4148158|access-date=}}</ref>
  }}
|Section7={{Chembox Hazards
| ExternalSDS = [https://www.sigmaaldrich.com/US/en/product/sigma/h3375]
| MainHazards = Eye Irritant
| NFPA-H = 1
| NFPA-F = 0
| NFPA-R = 1
| FlashPt = Non-flammable
| GHSPictograms = {{GHS07}}
| GHSSignalWord = Warning
| HPhrases = {{H-phrases|315|319|335}}
| PPhrases = {{P-phrases|261|264|270|271|280|301+312|302+352|304+312|304+340|305+351+338|312|321|322|330|332+313|337+313|362|363|403+233|405|501}}
  }}
}}

'''HEPES''' ('''4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid''') is a [[zwitterion]]ic [[sulfonic acid]] [[buffering agent]]. It is one of the twenty [[Good's buffers]]. HEPES is widely used in [[cell culture]], largely because it is better at maintaining physiological [[pH]] despite changes in [[carbon dioxide]] concentration (produced by [[aerobic respiration]]) when compared to bicarbonate buffers, which are also commonly used in cell culture. <ref>{{cite journal |vauthors=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}}</ref> Lepe-Zuniga ''et al.'' reported an unwanted [[photochemical]] process wherein HEPES catalyzes a reaction with [[riboflavin]] when exposed to ambient light to produce [[hydrogen peroxide]].<ref name="pmid3655381">{{cite journal |vauthors=Lepe-Zuniga JL, Zigler JS, Gery I |title=Toxicity of light-exposed Hepes media |journal= Journal of Immunological Methods|volume=103 |issue=1 |pages=145 |date=October 1987 |pmid=3655381 |doi=10.1016/0022-1759(87)90253-5     |url=http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+7722-84-1}}</ref><ref name="pmid4019356">{{cite journal |vauthors=Zigler JS, Lepe-Zuniga JL, Vistica B, Gery I |title=Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium|journal= In Vitro Cellular & Developmental Biology|volume=21 |issue=5 |pages=282–7 |date=May 1985 |pmid=4019356 |doi=10.1007/BF02620943 |s2cid=6557697 |url=http://toxnet.nlm.nih.gov/cgi-bin/sis/search/r?dbs+hsdb:@term+@rn+7722-84-1}}</ref> This is not a problem in bicarbonate-based cell culture buffers. It is therefore strongly advised to keep solutions containing both HEPES and riboflavin in darkness as much as possible to prevent [[oxidation]]. 

HEPES has the following characteristics: 
* p''K''<sub>a1</sub> (25&nbsp;°C) = 3
* p''K''<sub>a2</sub> (25&nbsp;°C) = 7.5
* Useful pH range = 2.5 to 3.5 '''or''' 6.8 to 8.2

HEPES has negligible metal ion binding,<ref>{{cite web |url=https://www.hopaxfc.com/en/blog/biological-buffers-and-their-interactions-with-metal-ions|title=Hopax Fine Chemicals - Biological buffers and their interactions with metal ions}}</ref> making it a good choice as a buffer for enzymes which might be inhibited by metal chelation.

==See also==
*[[CAPS (buffer) |CAPS]]
*[[CHES (buffer)|CHES]]
*[[MOPS]]
*[[HEPPS (buffer)|HEPPS]]
*[[MES (buffer)|MES]]
*[[HEPBS]]
*[[PIPES]]
*[[Buffer solution#Common buffer compounds used in biology|Common buffer compounds used in biology]]

==References==
{{reflist}}

{{DEFAULTSORT:Hepes}}
[[Category:Hydroxyethyl compounds]]
[[Category:Piperazines]]
[[Category:Buffer solutions]]
[[Category:Sulfonic acids]]
[[Category:Ethanolamines]]