DSIP: Research Reference

DSIP, delta sleep-inducing peptide, is a nine-amino-acid peptide, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, first isolated from rabbit blood in 1977 and named for the slow-wave EEG activity it produced in rabbits. It is a small, strongly acidic and very water-soluble peptide, and it is studied in animal and small human sleep-laboratory research, though its gene and receptor have never been identified.

This reference collects what a laboratory needs to know about DSIP as a material: how its nine residues behave in the vial, what it dissolves in, how it is handled at the bench and what to do when an order arrives. Each section below has its own page.

Molecular reference

Name	DSIP (delta sleep-inducing peptide)
Also known as	Emideltide, delta-sleep peptide, DSIP nonapeptide
Sequence	H-Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu-OH (WAGGDASGE; free N-terminal amine and C-terminal acid)
Residues	9
Molecular formula	C35H48N10O15
Molecular weight	848.8 g/mol
CAS number	62568-57-4

Formula, molecular weight, CAS number and synonyms are from PubChem (CID 68816). The same formula and weight appear on the Cayman Chemical product information sheet for emideltide acetate (item 34426), and the sequence on the InvivoChem data sheet (V64516).

Three features of that sequence explain most of its behaviour. Its only oxidation-prone residue is a tryptophan, and it sits at the very front of the chain, which is why light and dissolved oxygen are the main things to keep away from it (Li et al., Biotechnology and Bioengineering, 1995). It has one aspartic acid, at position 5, sitting between a glycine and an alanine: the Asp-Ala bond after it isomerises slowly, and the Gly-Asp bond before it is the kind that acid cleaves more readily (Oliyai and Borchardt, Pharmaceutical Research, 1994). And with an aspartate, a glutamate and the C-terminal acid against a single amine, it is strongly negatively charged and very hydrophilic, with no methionine, cysteine, histidine, tyrosine, asparagine or glutamine at all.

What it is studied for

DSIP was isolated from the cerebral venous blood of rabbits by the Schoenenberger and Monnier group in Basel. Infused into the brain ventricles of rabbits under double-blind conditions, it enhanced slow-wave (delta) and spindle EEG patterns, while its possible fragments and two rearranged analogues did not (Schoenenberger and Monnier, Proceedings of the National Academy of Sciences, 1977).

Its biology has remained hard to pin down. A 2006 review notes that no DSIP gene, precursor protein or receptor has been isolated, that the case for DSIP as a natural sleep factor is weak, and that DSIP-like immunoreactivity is concentrated in neurosecretory nuclei of the hypothalamus; the authors propose a related, still unidentified DSIP-like peptide (Kovalzon and Strekalova, Journal of Neurochemistry, 2006).

Human work is limited to small sleep-laboratory studies from the 1980s. In the first, six healthy volunteers in a double-blind crossover design showed a 59% rise in median total sleep time within a 130-minute window compared with placebo, without classic sedation (Schneider-Helmert et al., 1981). In a placebo-controlled, double-blind study of 14 middle-aged people with chronic insomnia, night-sleep efficiency reached the level of normal controls and daytime alertness rose (Schneider-Helmert, European Neurology, 1987). Our summary is in DSIP research: what the human studies show.

In blood, DSIP is broken down quickly: incubation in human or rat blood released products matching free tryptophan, at a rate that depended on temperature, time and species (Graf et al., Peptides, 1987).

Stability

With one tryptophan and one aspartate as its only sensitive points, DSIP is chemically simple. Its slow routes in solution are oxidation of the N-terminal tryptophan, driven by light and oxygen, and slow change at the aspartate. The DSIP stability page covers those routes, freeze-thaw, light and what visible changes mean.

Solubility

DSIP carries three acidic groups against one basic group, and one supplier rates its water solubility at about 100 mg/mL, so it dissolves in bacteriostatic water at once and needs no acid. The DSIP solubility guide explains why, which concentrations dissolve cleanly and what causes haze.

Handling

Bench practice for DSIP is mostly about keeping the solution cold, dark, clean and labelled. The DSIP handling page lists the steps and the common mistakes.

On arrival

What a sealed vial should look like, why it travels without an ice pack and where it and the ready-mixed spray go first are on the DSIP on-arrival page.

Storage and reconstitution

Fridge and freezer windows, before and after mixing, are on how long DSIP lasts. Water volumes and the concentration table for a 5 mg vial are on how much bacteriostatic water for a DSIP 5 mg vial.

FAQ

Short answers to the questions researchers ask most about storing, mixing and handling DSIP are on the DSIP FAQ.

Where to get it

Vistara Labs supplies DSIP 5 mg as a lyophilised vial for laboratory research, shipped within Canada by Canada Post Xpresspost. A ready-mixed DSIP Nasal Spray is also available. Certificates are on our lab reports page. For another short acidic peptide studied in circadian research, see the Epitalon research reference.