HEPES

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N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid); 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS NUMBER: 7365-45-9
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[[Image:HEPES structure.png|right|thumb|Chemical structure of HEPES = N-(2-'''h'''ydroxy'''e'''thyl)<br>'''p'''iperazine-N’-<br>(2-'''e'''thane'''s'''ulfonic acid);<br>aka 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS number: 7365-45-9]]
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A ''Good'' buffer [Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292]. Stable pH vs. temperature, no primary amine groups, no metal chelation, near physiologic pH range. HEPES is often used to maintain protein solubility in biochemical experiments.
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A ''Good'' buffer [Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292].
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Stable pH vs. temperature, no primary amine groups, no metal chelation, near physiologic pH range. HEPES is often used to maintain protein solubility in biochemical experiments.
* pK<sub>a</sub> at 25C of 7.55 (7.31 at 37C)
* pK<sub>a</sub> at 25C of 7.55 (7.31 at 37C)

Revision as of 10:36, 2 November 2011

Chemical structure of HEPES = N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid);aka 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS number: 7365-45-9
Chemical structure of HEPES = N-(2-hydroxyethyl)
piperazine-N’-
(2-ethanesulfonic acid);
aka 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS number: 7365-45-9

A Good buffer [Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292].

Stable pH vs. temperature, no primary amine groups, no metal chelation, near physiologic pH range. HEPES is often used to maintain protein solubility in biochemical experiments.

  • pKa at 25C of 7.55 (7.31 at 37C)
  • a second pKa at pH 3 is not of interest
  • usable buffering range of 6.8 to 8.2
  • molecular weight 238.3
  • ΔpKa/ΔT = -.014
  • HEPES contains tertiary amines, which are reactive under certain conditions.
  • See the structure of HEPES.
  • Chemical formula: C8H18N2O4S

Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide. HEPES is essentially insoluble until it is neutralized. and

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