HEPES, tissue culture grade

Hepes (N-2-hydroxyethyl) piperazine-N'-2-ethanesulfonic acid) is used in biochemistry, molecular biology, microbiology and cell culture as buffer substance with optimal buffer range at pH6.8-8.2 (pKa = 7.55 (20°C). Hepes is one of the "goods buffers." Dr. Norman Good et al. descriped in his work in 1966 a selection of "biological buffers" that display similar characteristics. These characteristics include: pKa value between 6.0 and 8.0, high solubility, non toxic, limited effect on biochemical reactions, very low absorbence between 240 nm and 700 nm, enzymatic and hydrolytic stability, minimal changes due to temperature and concentration, limited effects due to ionic or salt composition of the solution, limited interaction with mineral cations, and limited permeability of biological membranes.

Goods buffers are: BES, BICINE, CAPS, EPPS, HEPES, MES, MOPS, PIPES, TAPS, TES, TRICINE.

Reference:
Good N.E. et al. (1966) Hydrogen Ion Buffers for Biological Research, Biochemistry 5, 467-77.
Shipman jr. Ch. (1969) Proc. Soc. Exp. Biol. Med. 130, 305-10.