DSIP Peptide Dosage Units: Why a Unit Is Not a Mass

By What Peptides Editorial Team · Updated 2026-09-14 · Part of Peptide Handling Guides: Reconstitution Arithmetic, Storage and Testing

Delta sleep-inducing peptide, abbreviated DSIP, is a nine-residue peptide with the sequence Trp-Ala-Gly-Gly-Asp-Ala-Ser-Gly-Glu and a molecular mass of roughly 850 daltons. It was first isolated from rabbit brain tissue in the 1970s and has been studied since in sleep and stress physiology research. It is not an approved medicine in the United States, the European Union or the United Kingdom, and material carrying the name is typically sold as a research material rather than as a pharmaceutical. DSIP documentation is unusual among research peptides because figures for it circulate in both mass units and activity units, sometimes on the same listing, and that is where most reader confusion begins.

This page is about what a unit actually is. A unit is not a mass and cannot be turned into one by arithmetic alone. Converting units to milligrams requires a product-specific statement defining how many units correspond to how much material, and that statement is part of a product definition rather than a universal constant. Everything below is educational content about reading laboratory and research documentation. It is not medical advice, and it contains no dose, no schedule, and no suggestion that anyone should prepare or administer DSIP in any form.

What a Unit Measures

The word unit in pharmacology and biochemistry normally means an amount of biological activity, not an amount of substance. The classic version is the International Unit, or IU, which is defined against a physical reference standard: a committee assigns a potency to a preparation, and one IU is the activity contained in a stated amount of that preparation. Because the reference is a specific material measured in a specific assay, the IU is defined per substance. There is no general conversion from IU to grams, and asking for one is like asking how many kilograms there are in a litre. Any document that gives a unit figure should also say which reference standard and which assay define it.

Insulin is the case most readers have met. U-100 insulin is a product definition: 100 IU per mL. That ratio is not a law of nature that lets you convert insulin units to milligrams; it is a manufacturing standard that happens to be fixed, and it only lets you convert between units and volume for that product. Other concentrations, U-40 and U-500, use the same unit with a different volume relationship. Peptide research material sold without such a definition has no defensible units at all, and a listing that quotes units without stating what they refer to is incomplete documentation rather than a convertible number.

Enzyme units are a third case and make the point sharply. One enzyme unit is the amount of catalyst that converts a stated amount of substrate per minute under stated conditions, so the value depends on temperature, pH, substrate identity and the age of the preparation. It is a rate, not a quantity of material, and no conversion to mass exists even in principle. When a peptide document uses the word unit, the first question is always which of these three meanings applies, and the second is whether the document actually says.

Units, Mass and Volume Side by Side

DSIP documentation mostly uses micrograms, because the masses involved in research work are small and because the quantities that get written down in assay papers are in that range. A specification sheet typically gives a mass in mcg or mg, a purity percentage, and a molecular mass so that the reader can convert to moles. When a unit figure appears on the same page as a microgram figure, the two are describing different things: the microgram figure is how much material is present, and the unit figure, if it means anything at all, is how much activity a defined assay measured. They are not two ways of writing the same number, and treating them as such is the single most common error in this corner of documentation.

Molecular-mass arithmetic is the one conversion that is always available. Dividing a mass by the molecular mass gives an amount of substance in moles: 850 mcg of a peptide with a mass of 850 g per mol is 1 micromole. That conversion is exact and does not depend on the product at all. It is also the conversion people usually need when comparing two documents, because it normalises away both the arbitrary choice of mg versus mcg and the length of the peptide. For DSIP the figure sits near 850 g per mol; for larger therapeutic peptides it runs to several thousand, which is why a milligram of a large peptide is a much smaller number of moles than a milligram of a short one.

The Record-Keeping Fix: Log Four Fields Together

Unit and mass conversion errors are almost never arithmetic mistakes. They are context mistakes: a figure is copied out of one document into another, the definition travels with it incompletely or not at all, and months later nobody can tell whether the number meant mass or activity. The fix is procedural rather than mathematical. Every entry in a laboratory record for a peptide should carry four fields together on the same line, so that the number can never be separated from its meaning: the mass, the volume, the derived concentration, and the definition of any unit used. If a unit cannot be defined in writing, it should not be recorded at all.

The same discipline applies when material changes hands. A certificate of analysis should be filed with the lot number it describes, and that lot number should match the lot number on the vial, because a purity or peptide-content figure is only meaningful for a specific batch. Where a report gives peptide content as well as purity, record both, since they are different numbers; the distinction is set out in how purity and peptide content differ. This page is educational documentation practice for research material and is not medical advice. For the underlying chemistry, see the boundary between a peptide and a protein, and for the wider set, the peptide guides collection.

• Mass: in mg or mcg, with the unit written out in full
• Volume: in mL, including the identity of the diluent
• Concentration: derived mg/mL, calculated rather than assumed
• Unit definition: the exact wording from the specification sheet
• Lot number: matching the certificate of analysis on file
• Date: date of preparation and date the container was first opened

This page is part of the Peptide Handling Guides: Reconstitution Arithmetic, Storage and Testing guide.