The CAPS buffer, or 3-(cyclohexylamino)-1-propanesulfonic acid buffer, is a zwitterionic Good's buffer commonly used to maintain pH levels within the range of 9.7 to 11.1. This buffers support several applications including protein crystallization, enzymatic reactions, and western and immunoblotting experiments. It is an excellent buffer for the transfer of proteins with high molecular weights to nitrocellulose membranes after SDS-PAGE. CAPS buffer can also be used in protein sequencing.