4654. HEPES

Nomenclature

CAS number: 7365-45-9
4-(2-Hydroxyethyl)-1-piperazineethanesulfonic acid; N-(2-hydroxyethyl)piperazine-N′-2-ethanesulfonic acid.
C8H18N2O4S; mol wt 238.30.
C 40.32%, H 7.61%, N 11.76%, O 26.86%, S 13.46%.

Description and references

One of several zwitterionic N-substituted aminosulfonic acids known as Good Buffers, active in the pH range of 6-8.5. Prepn: N. E. Good et al., Biochemistry 5, 467 (1966). Buffering characteristics: W. J. Ferguson et al., Anal. Biochem. 104, 300 (1980). Temperature effects on pKa and pH: R. N. Roy et al., Cryo Letters 6, 285 (1985). Interaction with hydroxyl radicals: M. Hicks, J. M. Gebicki, FEBS Lett. 199, 92 (1986). Interference with Lowry protein determination: H. M. Himmel, W. Heller, J. Clin. Chem. Clin. Biochem. 25, 909 (1987). Use as biological buffer: H. Eagle, Science 174, 500 (1971); K. V. Rao, Indian J. Exp. Biol. 15, 552 (1977); E. D. Lalague et al., J. Microsc. 127, 307 (1982); G. I. McFadden, M. Melkonian, Phycologia 25, 551 (1986).

Chemical structure

Properties

Crystals from alcohol + water, mp 234°. pKa1 3, pKa2 (20°) 7.55. ΔpKa/°C 0.014. Saturated aqueous soln is 2.25M at 0°.

Use

Biological buffer.