CAPS (3-cyclohexylamino-1-propanesulfonic acid) is a zwitterionic buffer used in biological and biochemical research to maintain stable pH in strongly alkaline systems. It is especially useful for high-pH applications where standard near-neutral buffers are not effective.

• pKa (25 °C): ~10.4
• Effective buffering range: pH 9.7–11.1
• Highly soluble in water
• Low UV absorbance
• Minimal interaction with proteins and enzymes

CAPS is commonly used in protein research, high-pH enzyme assays, Western blot transfer buffers, and other applications requiring reliable buffering at alkaline pH.