Citrulline-specific probe-biotin is a biotinylated probe designed for detecting citrulline, the hydrolysis product of the amino acid arginine catalyzed by protein arginine deiminase (PAD). This probe is useful in identifying diseases with abnormally increased PAD activity, as elevated levels of citrulline are indicative of such conditions. Citrulline-specific probe-biotin has proven effective in applications within animal models of ulcerative colitis, demonstrating its utility in biomedical research and diagnostics.