HEPES

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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.  
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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A ''Good'' buffer [Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292].
 
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Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide.  HEPES is essentially insoluble until it is neutralized.
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 ==
 +
* 700 ml ultrapure water
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* 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 ==
== Links ==
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* original publications: Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292
* [http://en.wikipedia.org/wiki/Buffer_solution Wikipedia: buffer solution]
* [http://en.wikipedia.org/wiki/Buffer_solution Wikipedia: buffer solution]
* [http://www.scribd.com/doc/12568914/Common-Buffers-Media-And-Stock-Solutions CP: common buffers]
* [http://www.scribd.com/doc/12568914/Common-Buffers-Media-And-Stock-Solutions CP: common buffers]
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[[Category:Material]] and [[Category:Buffers]]
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[[Category:Material]]
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[[Category:Buffers]]

Revision as of 10:54, 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

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)
  • 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.
  • Chemical formula: C8H18N2O4S

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

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