sh-Oligopeptide-281 SP is a single chain human peptide produced synthetically and inspired by the protein, Human Pulmonary Surfactant-Associated Protein D, and contains 23 amino acids consisting of alanine, cysteine, glutamic acid, glutamine, glycine, histidine, leucine, lysine, phenylalanine, proline, serine, tyrosine and valine. Human Pulmonary Surfactant-Associated Protein D contains a maximum of 237 amino acids which may contain disulfide bonds and/or glycosylation. It consists of the proper sequence of the 20 standard amino acids.