Modification of free-thiol group(s) in a protein is one of the typical posttranslational modifications and such modification is controlled by in vivo redox responses. In recent studies, it has been investigated that the modified free-thiol group controls many of cellular responses, e.g. cell death, protein expression, transcription.This kit is designed to monitor the number of thiol group in protein with very simple procedure, and the number of thiol group can be monitored by electrophoresis (Code#: SB11) and western blotting (Code#: SB12).