N-Cyclohexyl-3-aminopropanesulfonic, abbreviated as CAPS, 2-(Cyclohexylamino)ethanesulfonic acid, abbreviated as CHES, both of them are commonly used buffering reagents in biochemical and molecular experiments. You may find it strange to compare them? Let's take a look at the following contents.

Similarity of CAPS and CHES

Both CAPS (CAS 1135-40-6) and CHES are zwitterionic buffers, their buffering range are in alkaline range and higher than the commonly used physiological range. Although they are not introduced by Good et al., they are also called as Good’s Buffers sometime. They are both not complexed with metal ions.

Differences in Structures and Property

The molecular formulas of CAPS and CHES are C9H19NO3S and C8H17NO3S, respectively. They have the same structure of cyclohexylamino, but different carbon chain lengths, as shown below:

The pKa value of CHES is 9.5 at 25°C and pH buffer range of 8.6~10.0; The pKa value of CAPS is 10.4 at 25°C, and buffer range is 9.7~11.1. The longer sulfonic acid carbon chains make it more alkaline than CHES.

Differences in Applications

The applicationS of CAPS:

(1) Transfer buffer for diffusion blotting and electroblotting; Binding buffer and eluent in cation exchange chromatography; Running buffer in capillary electrophoresis; Enzyme assay buffer

(4) Suitable for use with the Bicinchoninic Acid (BCA) Assay.

(5) Inhibiting the viability of Micrococcus luteus at pH 9.5.

In summary, CAPS and CHES have some similarity in structure and property, but there are also many differences in application, so careful analysis is needed before use to select the most appropriate buffer.