Delta sleep-inducing peptide (DSIP) is a naturally occurring nonapeptide — a chain of nine amino acids — with the sequence Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu. Its molecular formula is C₃₅H₄₈N₁₀O₁₅, with a molecular weight of 848.81 g/mol (CAS 62568-57-4). DSIP was first isolated in 1977 from the cerebral venous blood of rabbits during induced sleep by a Swiss research group.

The peptide is classified as amphiphilic, meaning it has both water-attracting and water-repelling regions, a property related to its mixed hydrophilic and hydrophobic amino acid residues. The tryptophan residue at the N-terminus gives it a characteristic UV absorbance profile used for laboratory identification. DSIP is notable for its low molecular weight and amphiphilic structure — the selective membrane separating circulating blood from brain tissue. In its research-grade form, it appears as a white lyophilized powder that dissolves in water.

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PubChem Reference: View compound profile on NIH PubChem