sh-Pentapeptide-13 SP is a single chain human peptide produced synthetically to be identical to a portion of the protein, Histone H4, and contains 5 amino acids consisting of glycine, phenylalanine and tyrosine. The parent protein contains a maximum of 103 amino acids which may contain disulfide bonds and/or glycosylation, and consists of the proper sequence of the 20 standard amino acids.