HEPES
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| Names | |
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IUPAC name
2-[4-(2-hydroxyethyl)piperazin-1-yl]ethanesulfonic acid
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| Other names
HEPES
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| Identifiers | |
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3D model (Jmol)
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| ChEBI | |
| ChemSpider | |
| ECHA InfoCard | 100.028.098 |
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PubChem CID
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| RTECS number | TY2900000 |
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| Properties | |
| C8H18N2O4S | |
| Molar mass | 238.3012 g/mol |
| Appearance | white crystalline powder |
| Density | Not applicable |
| Melting point | >234-238°C (453-457K) |
| 40 g/100 ml (20°C) | |
| Acidity (pKa) | 3 (pKa1), 7.5 (pKa2) |
| Hazards | |
| Main hazards | Irritant. |
| Safety data sheet | External MSDS |
| R-phrases | R36, R37, R38. |
| S-phrases | S26, S36. |
| NFPA 704 | |
| Flash point | Non-flammable |
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Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
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 (what is   ?) |
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| Infobox references | |
HEPES (4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid ) is a zwitterionic organic chemical buffering agent; 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 cellular respiration) when compared to bicarbonate buffers, which are also commonly used in cell culture. The dissociation of water decreases with falling temperature, but the dissociation constants (pK) of many other buffers do not change much with temperature. HEPES is like water in that its dissociation decreases as the temperature decreases. This makes HEPES a more effective buffering agent for maintaining enzyme structure and function at low temperatures. Lepe-Zuniga et al. reported a phototoxicity of HEPES when exposed to ambient light by the production of hydrogen peroxide, which is not a problem in bicarbonate-based cell culture buffers. It is therefore strongly advised to keep HEPES-containing solutions in darkness as much as possible.
HEPES has the following characteristics:
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