Difference between revisions of "HEPES"

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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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[[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)]]
  
A ''Good'' buffer [Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292].
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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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== 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.
 
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)
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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)
* a second 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
* 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
 
* HEPES contains tertiary amines, which are reactive under certain conditions.  
 
* HEPES contains tertiary amines, which are reactive under certain conditions.  
* See the structure of [http://store.p212121.com/products/HEPES-500-g.html HEPES].
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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
* Chemical formula: C<sub>8</sub>H<sub>18</sub>N<sub>2</sub>O<sub>4</sub>S
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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
  
Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide.   HEPES is essentially insoluble until it is neutralized.
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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]
  
  
[[Category:Material]] and [[Category:Buffers]]
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[[Category:Material]]
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[[Category:Buffers]]

Latest revision as of 07:57, 2 November 2011

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.

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