A nucleosome is the basic repeating unit of chromatin in which 146 base pairs of DNA wrap twice around a histone octamer consisting of two copies of each of the core histones, H2A, H2B, H3, and H4. The combination of two H2A/H2B dimers and one H3/H4 tetramer create the nucleosome core. Histone H3 undergoes many modifications which include acetylation, methylation, and phosphorylation that are important for regulation of gene transcription. Citrullination is another important post-translational modification that this catalyzed the by enzymes peptidylarginine deiminases (PAD4 and PAD2). Hypercitrullination of histones leads to the development of neutrophil extracellular traps (NETs), which are a part of the inflammatory response. Neutrophils release these NETs to trap and eradicate bacteria and fungi. Failure to clear citrullinated proteins and NET components following inflammation can result in the production of autoantibodies and anti-citrullinated protein antibodies. The persistence of these antibodies and citrullinated proteins is associated with a number of human diseases including rheumatoid arthritis, systemic lupus erythematosus, Alzheimer"s disease, and multiple sclerosis. This product contains purified Histone H3 (human recombinant) (Cay-10263) that has been modified with PAD4 enzyme, which is removed by affinity chromatography after the reaction.