HEPES and PIPES are two types of sulfonic acid group containing biological buffer. They belong to Good’s buffer family and are especially dedicated to life science research that does not participate in and does not interfere with biochemical processes.

PIPES has a pH buffer range from 6.1 to 7.5, is insoluble in water, but soluble in aqueous NaOH. PIPES differs from buffers containing bis(2-hydroxyethyl)amino groups (such as Bis-tris, Bicine) which does not form stable complexes with most metal ions. It is suitable for buffers in solution systems containing metal ions. According to the existing research results, PIPES can be applied to purify microtubule proteins using phosphocellulose chromatography, to purify recombinant GTP-binding proteins ARF1 and ARF2 by gel filtration, and as a buffer solution to crystallize a transketolase enzyme from E. coli. In addition, PIPES can form radicals and therefore not suitable for redox reactions. In cation exchange chromatography, low concentrations of PIPES buffer should be used because PIPES has a relatively large ionic strength and its pKa value depends on concentration.

The pH buffer range of HEPES is from 6.8 to 8.2. It is soluble in water and does not form stable complexes with metal ions. In most cases, it will not interfere with biochemical processes. HEPES is commonly used in cell culture media for various types of organisms; PIPES is commonly used as a binding buffer and an eluent during cation exchange chromatography for protein studies; in DNA studies, PIPES is used as a buffer to form precipitates of calcium phosphate and DNA, and as a buffer in AFM and electroporation experiments. In addition, HEPES interferes with the reaction between DNA and restriction enzymes, and is not suitable for use with the Lowry method of protein content.

In summary, PIPES and HEPS are Good's buffers, which do not form stable complexes with metal ions and are suitable for solution systems containing metal ions. However, there is also a certain difference between them. In terms of solubility, PIPES is insoluble in water, while HEPES has good water solubility; in terms of buffer range, PIPES is acidic to neutral, and HEPES is neutral to alkaline, which is mainly due to the structural differences between them, PIPES has two sulfonic acid groups, and HEPES contains a sulfonic acid group and a hydroxyl group. In addition, PIPES and HEPES have certain limitations in concrete applications. Therefore, when choosing the above buffer, we need to consider the suitability of the experimental system and the different nature of them.

Edited by Suzhou Yacoo Science Co., Ltd.