HEPES
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N-(2-hydroxyethyl)piperazine-N’-(2-ethanesulfonic acid); 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid; CAS NUMBER: 7365-45-9
A Good buffer [1][2][3]. Stable pH vs. temperature, no amine groups, no metal chelation, near physiologic pH range.
- 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
Buffers are typically 1 M, prepared by neutralizing HEPES with sodium hydroxide. HEPES is essentially insoluble until it is neutralized.
- Good NE, Winget GD, Winter W, Connolly TN, Izawa S, and Singh RM. Hydrogen ion buffers for biological research. Biochemistry. 1966 Feb;5(2):467-77. DOI:10.1021/bi00866a011 |
- Good NE and Izawa S. Hydrogen ion buffers. Methods Enzymol. 1972;24:53-68. DOI:10.1016/0076-6879(72)24054-x |
- Blanchard JS. Buffers for enzymes. Methods Enzymol. 1984;104:404-14. DOI:10.1016/s0076-6879(84)04107-0 |
