Peptide Solution Reference
Peptide Solution Reference
A laboratory reference for preparing research peptide solutions: how concentration follows from mass and volume, how to move between units, and the molar mass of each catalogued compound so that a mass concentration can be read as a molarity. It replaces the interactive calculator that used to sit on this page.
Mass, volume and concentration
Concentration is the mass of material divided by the volume of solvent it is dissolved in. Ten milligrams dissolved in two millilitres gives 5 mg/mL; the same ten milligrams in five millilitres gives 2 mg/mL. The figure describes the solution as a whole and says nothing about how it is used afterwards.
| This | is the same as |
|---|---|
| 1 mg/mL | 1 µg/µL, 1,000 µg/mL, 1 g/L |
| 1 µg/mL | 1 ng/µL, 0.001 mg/mL |
| 1 mL | 1,000 µL, 1 cm³ |
| 1 mg | 1,000 µg, 0.001 g |
From mass concentration to molarity
Molarity depends on the molecular weight of the compound. A 1 mg/mL solution of a compound of molecular weight 1,000 Da is 1 mM; a compound twice as heavy gives half the molarity at the same mass concentration.
- millimolar (mM) = (mg/mL ÷ molecular weight in Da) × 1,000
- mg/mL needed for a target molarity = target mM × molecular weight ÷ 1,000
- micromolar (µM) = mM × 1,000
Molar masses of catalogued compounds
Molecular weights are those stated on each compound’s own product page, with the basis the page gives. Where a peptide is supplied as an acetate salt the free-base figure overstates the molarity of a weighed sample slightly, because part of the weighed mass is counter-ion; the certificate of analysis for the lot supplied records peptide content and water content, which are the figures to use for exact work. Blends, small-molecule compounds and solvents are not listed.
| Compound | Molecular weight (Da) | Basis as stated | 1 mg/mL is | 1 mM needs |
|---|---|---|---|---|
| BPC-157 | 1,419.55 | free base, monoisotopic | 0.704 mM | 1.42 mg/mL |
| CJC-1295 without DAC (Modified GRF 1-29) | 3,367.97 | free base, monoisotopic | 0.297 mM | 3.37 mg/mL |
| DSIP | 848.8 | free acid, average | 1.18 mM | 0.849 mg/mL |
| GHK-Cu | 403.9 | copper-peptide complex | 2.48 mM | 0.404 mg/mL |
| Glutathione (GSH) | 307.32 | reduced form | 3.25 mM | 0.307 mg/mL |
| Ipamorelin | 711.87 | free base, monoisotopic | 1.4 mM | 0.712 mg/mL |
| Kisspeptin-10 | 1,302.5 | free base, average | 0.768 mM | 1.3 mg/mL |
| KPV | 342.44 | free base | 2.92 mM | 0.342 mg/mL |
| MOTS-c | 2,174.6 | free base | 0.46 mM | 2.17 mg/mL |
| Melanotan I (MT-1) | 1,646.8 | free base, average | 0.607 mM | 1.65 mg/mL |
| Melanotan II (MT-2) | 1,024.2 | free base, average | 0.976 mM | 1.02 mg/mL |
| NAD+ | 663.4 | free acid | 1.51 mM | 0.663 mg/mL |
| PT-141 (bremelanotide) | 1,025.2 | free acid, average | 0.975 mM | 1.03 mg/mL |
| Selank | 751.9 | free base, average | 1.33 mM | 0.752 mg/mL |
| Semax | 813.9 | free base | 1.23 mM | 0.814 mg/mL |
| SNAP-8 (acetyl octapeptide-3) | 1,075.15 | free base, monoisotopic | 0.93 mM | 1.08 mg/mL |
| SS-31 (elamipretide) | 639.8 | free base | 1.56 mM | 0.64 mg/mL |
| Tesamorelin | 5,135.8 | free base | 0.195 mM | 5.14 mg/mL |
| Thymosin alpha-1 | 3,108.28 | free base, monoisotopic | 0.322 mM | 3.11 mg/mL |
What the arithmetic does not know
Solubility. A concentration that is arithmetically valid may not be achievable. Some peptides will not go into solution at neutral pH at higher concentrations, which is why two reconstitution solvents are stocked rather than one; see the format guide and the reconstitution and handling hub.
Stated mass versus peptide content. A vial labelled at a given mass contains that mass of supplied material. Residual moisture and counter-ions mean peptide content can be lower, which is why water content appears on the certificate.
Laboratory reference only. This page relates mass, volume and concentration for in-vitro laboratory work. It gives no withdrawal, dose or administration figures, and nothing on it should be read as guidance for preparing material for use in humans or animals.