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)]]
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A Good buffer <cite>Good66</cite><cite>Good74</cite><cite>Blanchard84</cite>.  Stable pH vs. temperature, no amine groups, no metal chelation, near physiologic pH range.
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HEPES is a common buffering chemical similar to Tris in Tris-HCl buffers and phosphates in PBS. Buffers are used to keep the pH at a certain value and can "buffer" the addition of small amounts of acids/bases.  
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* pK<sub>a</sub> at 25C of 7.55 (a second one at pH 3 is not of interest)
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== Property of HEPES ==
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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.
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* pK<sub>a</sub> at 25C of 7.55 (7.31 at 37C); (2nd pK<sub>a</sub> at pH 3 is not of interest)
* usable buffering range of 6.8  to 8.2
* usable buffering range of 6.8  to 8.2
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* molecular weight 238.3
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* molecular weight 238.3 g/mol
* &Delta;pK<sub>a</sub>/&Delta;T = -.014
* &Delta;pK<sub>a</sub>/&Delta;T = -.014
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* HEPES contains tertiary amines, which are reactive under certain conditions.
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* Chemical formula: C<sub>8</sub>H<sub>18</sub>N<sub>2</sub>O<sub>4</sub>S;  N-(2-hydroxyethyl)-piperazine-N’-(2-ethanesulfonic acid); aka 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS number: 7365-45-9
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Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide. HEPES is essentially insoluble until it is neutralized.
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== 1M HEPES KOH buffer 7.5 ==
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* 700 ml ultrapure water
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* 238.3 g HEPES
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* KOH (potassium hydroxide) pellets to adjust pH to 7.5
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* to 1L w ultrapure water; sterilise by filtration
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== 1M HEPES-NaOH pH 7.5 ==
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* 700 ml ultrapure water
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* 238.3 g HEPES
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* ~5.5 g NaOH (sodium hydroxide) pellets to adjust pH to 7.5
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* to 1L w ultrapure water; sterilise by filtration
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== Links ==
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* original publications: Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292
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* [http://en.wikipedia.org/wiki/Buffer_solution Wikipedia: buffer solution]
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* [http://www.scribd.com/doc/12568914/Common-Buffers-Media-And-Stock-Solutions CP: common buffers]
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* [http://www.science.smith.edu/departments/Biochem/Biochem_353/Common_Buffers.html List of common buffers from Smith College]
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Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide.  HEPES is essentially insoluble until it is neutralized.
 
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<biblio>
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[[Category:Material]]
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# Good66 pmid=5942950
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[[Category:Buffers]]
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# Good74 pmid=4206745
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# Blanchard84 pmid=6717292
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</biblio>
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Current revision

Chemical structure of HEPES = N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid)
Chemical structure of HEPES = N-(2-hydroxyethyl)
piperazine-N’-
(2-ethanesulfonic acid)

HEPES is a common buffering chemical similar to Tris in Tris-HCl buffers and phosphates in PBS. Buffers are used to keep the pH at a certain value and can "buffer" the addition of small amounts of acids/bases.

Contents

Property of HEPES

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); (2nd pKa at pH 3 is not of interest)
  • usable buffering range of 6.8 to 8.2
  • molecular weight 238.3 g/mol
  • ΔpKa/ΔT = -.014
  • HEPES contains tertiary amines, which are reactive under certain conditions.
  • Chemical formula: C8H18N2O4S; N-(2-hydroxyethyl)-piperazine-N’-(2-ethanesulfonic acid); aka 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS number: 7365-45-9

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

1M HEPES KOH buffer 7.5

  • 700 ml ultrapure water
  • 238.3 g HEPES
  • KOH (potassium hydroxide) pellets to adjust pH to 7.5
  • to 1L w ultrapure water; sterilise by filtration

1M HEPES-NaOH pH 7.5

  • 700 ml ultrapure water
  • 238.3 g HEPES
  • ~5.5 g NaOH (sodium hydroxide) pellets to adjust pH to 7.5
  • to 1L w ultrapure water; sterilise by filtration

Links

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