This kit provides the reagents required for the detection of citrulline-containing proteins by Western blot analysis with the anti-Citrulline antibody. Detection is a two-step process in which citrulline-containing proteins immobilized on nitrocellulose or PVDF are formaldehyde-cross linked to the membrane to improve protein retention, followed by modification of citrulline residues with 2,3-butanedione monoxime and antipyrine in a strong acid solution to form a ureido group adduct. This ensures detection of citrulline-containing proteins regardless of neighboring amino acid sequences. Detection of the modified citrulline proteins is subsequently performed using a standard immunoblot protocol with the anti-Citrulline and goat anti-rabbit IgG-HRP.