HEPES
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| - | N-(2- | + | [[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)]] |
| - | + | 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. | |
| - | * pK<sub>a</sub> at 25C of 7.55 (7.31 at 37C) | + | == 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. | ||
| + | |||
| + | * 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 | ||
| - | * molecular weight 238.3 | + | * molecular weight 238.3 g/mol |
* ΔpK<sub>a</sub>/ΔT = -.014 | * ΔpK<sub>a</sub>/ΔT = -.014 | ||
| - | *HEPES contains tertiary amines, which are reactive under certain conditions | + | * HEPES contains tertiary amines, which are reactive under certain conditions. |
| - | *Chemical formula: C<sub>8</sub>H<sub>18</sub>N<sub>2</sub>O<sub>4</sub>S | + | * 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 |
| + | |||
| + | 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 == | |
| - | + | * 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://www.scribd.com/doc/12568914/Common-Buffers-Media-And-Stock-Solutions CP: common buffers] | |
| - | + | * [http://www.science.smith.edu/departments/Biochem/Biochem_353/Common_Buffers.html List of common buffers from Smith College] | |
| - | [[Category:Material]] | + | [[Category:Material]] |
| + | [[Category:Buffers]] | ||
Current revision
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
- original publications: Good'66 PMID 5942950, Good'74 PMID 4206745, Blanchard'84 PMID 6717292
- Wikipedia: buffer solution
- CP: common buffers
- List of common buffers from Smith College
