This peptide is histone H4 amino acid residues 1 to 21. It is phosphorylated at Ser-1 with an acetylated N-terminus and C-terminal GG linker, followed by a biotinylated Lys. Phosphorylation of histone 4 at Ser-1 is involved in the regulation of cell-cycle responses to DNA damage. Provided at >95% peptide purity, this peptide was dissolved in distilled water at 1 mg/ml and re-lyophilized to powder form.