DSIP peptide: sequence, molecular data, certificate of analysis, sizes

DSIP is an acronym coined in 1977 for a nine-residue peptide isolated from rabbit cerebral venous blood by Schoenenberger and Monnier.

Everything sold under that name today is made by solid-phase synthesis, not extracted from anything: the sequence is short, it contains no cysteine and therefore no disulfide bridge, and it assembles without difficulty.

Nine residues is small. For comparison, KPV is three, Selank is seven, Semax is seven, and BPC-157 is fifteen.

A nonapeptide sits at the size where a single chromatographic run resolves the target from its truncated by-products cleanly, which is why purity figures on this compound are usually high and why a low one is a red flag rather than a limitation of the chemistry.

Research use only. Not for human or veterinary use.

Two residues in the sequence carry the mass.

Tryptophan at position one is the bulkiest of the twenty proteinogenic amino acids and the only one in the chain that shows strongly in the UV at 280 nm, which gives a laboratory a second handle on the compound alongside the 214 nm peptide-bond signal.

Glutamic acid at position nine and aspartic acid at position five make the chain acidic, which is why it dissolves in plain water rather than needing a solvent trick.

The three glycines (positions three, four and eight) are the reason the chain is flexible and the reason a synthesis run produces so few deletion by-products: glycine couples fast.

A synthetic peptide that carries basic residues is purified by preparative HPLC in a mobile phase containing trifluoroacetic acid, then exchanged onto acetate before freeze-drying.

The vial therefore holds three things: the peptide, its acetate counter-ions, and residual water that the lyophilizer could not pull out.

The practical consequence is one line on the certificate: the net peptide content, the share of the labelled powder that is the peptide chain itself, as opposed to counter-ion and water.

A full certificate states it. It is not a defect, it is what a lyophilized salt is; a laboratory computing a concentration divides by the net figure rather than by the label.

A supplier who states the filled mass and never the net content is not lying. The buyer is simply paying for a number nobody has measured.

Further reading: epithalon (AEDG) data sheet, TB-500 data sheet, glutathione (GSH) data sheet and Sermorelin peptide.

A batch certificate for a nonapeptide is short, and four lines carry the whole document.

• Purity by reverse-phase HPLC. One main peak, its area against total peak area, detected at 214 nm. On a nine-residue chain a figure above 98 % is ordinary and a figure below 95 % points at a synthesis that went wrong rather than at a hard sequence.
• Identity and quantity. The compound found, named by the laboratory, and the mg measured. If a lab adds mass spectrometry as an option, the mass lands near 848.8: 57 lower means a missing glycine, 87 lower a missing serine, 42 higher an acetylated by-product.
• Net peptide content, by amino-acid analysis or nitrogen determination. The field discussed above.
• Lot number, date, laboratory name, and a photograph of the labeled vial. The four fields that tie the document to the object in hand rather than to a production run somewhere.

How to read each field, and how to check a report number against the laboratory itself, is in how to read a Janoshik test report and in how to read a peptide COA.

The published Janoshik reports (Retatrutide 10, 20 and 30 mg, GHK-Cu 100 mg) are in the COA library.

DSIP is supplied in one size, a 10 mg vial.

There is no 5 mg or 20 mg format: at this molecular mass and this price per milligram, a smaller vial would cost almost as much to fill, label and certify as the 10 mg one, and a larger one would sit open longer than a laboratory wants.

The catalog card at the top of this page reads the live price and the live stock from the catalog, so it never contradicts the product page.

DSIP is a lower-volume reference: when the card shows it as unavailable, the supply is between lots rather than discontinued, and the notification field on the DSIP product page is the way to hear when a lot lands.

Other short regulatory peptides in the same family are Selank, Semax and Epithalon.

What the price includes at OXpeptides: a sealed, labeled vial and the lyophilized compound inside, named with its net quantity in mg on the label. Ships from the EU · tracked: €9.90, free from €120.

See DSIP in the catalog →

• Temperature: −20 °C for long-term storage, in the sealed vial.
• Light and moisture: keep the vial sealed and in its box. Let a cold vial reach room temperature before it leaves its bag, so no condensation forms on the glass and none of it reaches the powder.
• Shelf life: 24 months for a sealed lyophilized vial stored as above; the date printed on the label governs.
• In solution: far less stable than the dry cake. Freeze-thaw is what destroys a short peptide in solution, not time on the shelf.

Ambient shipping over a few days does not degrade a sealed lyophilized powder, which is why research peptides travel without cold packs. Compound by compound, the rules are in lyophilized peptides: storage and shelf life.

Further reading: CJC-1295 / Ipamorelin blend.

A search for this compound returns pharmacies, encyclopaedia entries, journal abstracts and a handful of research suppliers. The listing worth reading answers five questions on the page itself.

1. Is the sequence printed? Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, nine residues. A page that names the compound and never writes the sequence has nothing to check.
2. Is the mass stated, and is it 848.8? A page giving a different figure is describing a different molecule or copying a different data sheet.
3. Is there a batch certificate from a named independent laboratory, with a task number and verification key the laboratory confirms, a date, and a photograph of the labeled vial?
4. Is the vial sealed, labeled and lyophilized, with a stated size? A listing that sells a solution has made a choice about storage on your behalf.
5. Does the page describe the reagent only (sequence, mass, purity documentation, storage), with research use only stated plainly? A supplier who publishes usage content is a supplier easy to shut down, and the parcel in transit belongs to the buyer.

The seven-point method, including what a re-used or edited certificate looks like, is in how to check a peptide supplier. The Europe-wide checklist is in where to buy research peptides in Europe.

DSIP is a nonapeptide, Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu, formula C₃₅H₄₈N₁₀O₁₅.

Its average mass, 848.8 g/mol, is the figure used to weigh the powder. The mass spectrum on a certificate shows different numbers, and it helps to know which ones to expect:

• Monoisotopic mass: about 848.3 Da.
• [M+H]⁺: about 849.3, the singly charged ion, usually the main signal for a peptide this size.
• [M+2H]²⁺: about 425.2, often weak, since DSIP carries no lysine or arginine to hold a second proton.
• [M+Na]⁺: about 871.3, a sodium adduct some spectra show next to the main ion.

A certificate that prints the observed mass lets anyone compare it with these values. One that writes "conforms" with no number asks the reader to trust it.

DSIP is short, rich in glycine (three of nine residues) and acidic: one aspartic acid, one glutamic acid, no basic residue.

On a reversed-phase column it is not strongly retained, and the method has to be adapted so that the peak does not come out too close to the solvent front.

Its first residue is a tryptophan.

Tryptophan absorbs ultraviolet light at 280 nm, where most other residues do not, so a laboratory can read DSIP at 280 nm as well as at the usual 214-220 nm of the peptide bond.

Two wavelengths that agree on the purity make a stronger reading than one.

The weak points of the sequence are known: the Asp-Ala bond and the Asp side chain can rearrange slowly in solution, and tryptophan can oxidise if the powder is exposed to light and air.

Both show up as small extra peaks or a +16 Da mass. That is the practical reason behind the storage rules of the sealed vial: cold, dark, dry, opened as late as possible.

A 10 mg DSIP vial should hold 10 mg of peptide.

The lyophilized powder also contains the acetate counter-ion and a few percent of residual water, so the powder weighs more than the peptide it carries.

A supplier that states the net peptide content, or a quantity measured on the lot, shows the figure that matters; a supplier that only states "10 mg" leaves the question open.

Compare suppliers on three lines: the mass confirmed on the certificate, the purity, and the quantity in the vial.

Only then does the price per mg mean something. A general method for this is set out in how to check a peptide supplier. Research use only. Not for human or veterinary use.

All four are short, all four are sold as lyophilized acetate salts, and all four are identified the same way: a main HPLC peak and a mass that matches the sequence.

DSIP is the only one of the four with a tryptophan, which gives it a second reading wavelength at 280 nm.