What is DSIP?
The molecular reference for this catalog records the sequence H-Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu-OH across nine residues. The chain is small, unusually flexible because of its three glycines, and distinctly acidic, with an aspartate and a glutamate and no basic residue at all. The single tryptophan at the amino terminus is the only aromatic group and is the feature that dominates both its ultraviolet absorbance and its sensitivity to light and oxidation.
DSIP was described after perfusate from rabbits in a particular sleep state was transferred to recipient animals, and the peptide was named for the delta wave activity observed in those experiments. Subsequent rodent and cell model work has examined it in relation to sleep architecture measures, corticotropin release, and stress response markers in the animals studied (Graf and Kastin, 1984).
The unsettled part is large. No specific receptor has been identified, the original transfer experiments have not been cleanly replicated, and the peptide is detected in tissues where a sleep related role is hard to rationalise. Reported effects vary with species and assay, so the published record reads as descriptive rather than mechanistic.
Reconstitution & handling
Sterile or bacteriostatic water is added slowly down the vial wall with gentle swirling, and the small acidic sequence dissolves quickly at neutral pH. Vigorous agitation is avoided because it introduces air and accelerates oxidation of the tryptophan. Concentration is plain arithmetic, so 2 mL added to a 5 mg vial yields 2.5 mg per millilitre. A yellow tint suggests tryptophan degradation.
Storage & stability
Sealed lyophilized vials are stored at -20 °C, protected from light and moisture, and brought to room temperature before the stopper is pierced. Light protection matters more than usual here because tryptophan is photolabile and its oxidation products are the first new peaks to appear on chromatography. Reconstituted solution is refrigerated at 2 to 8 °C in amber or foil wrapped vials, aliquoted for single use, and protected from repeated freezing and thawing.
How it's tested
Lots are analysed by reversed phase HPLC at 214 and 220 nm and reported at 99 percent or greater main peak area, with the tryptophan giving a confirmatory signal at 280 nm. Mass spectrometry confirms identity against the theoretical average mass of 848.81 derived from C35H48N10O15, and also reveals the characteristic mass shifts of oxidised tryptophan when present. A lot-matched certificate is available on request.