Dissolving peptides: reconstitution step by step

In reconstitution you dissolve a freeze-dried powder in a known volume of solvent, so you get a solution of known concentration. A peptide is more stable freeze-dried than in solution, which is why you only dissolve a vial when you need it.

Which solvent suits a material is on the product page, the data sheet or the certificate. If in doubt, dissolve a small part first.

• Bac water: sterile water with 0.9% benzyl alcohol as a preservative. The usual choice when you use a vial over several days.
• Acetic acid water: sterile water with dilute acetic acid. For peptides rich in basic amino acids that dissolve poorly at neutral pH.
• Sterile water: without preservative. Suitable when you use the solution in one go, or when your material does not tolerate benzyl alcohol.

• Work cleanly: gloves, a disinfected work surface and an alcohol wipe over the rubber stopper of both vials.
• Let the powder vial and the solvent reach room temperature. If you open a cold vial, moisture from the air condenses on the powder.
• Add the solvent sterile and slowly along the wall of the vial, not directly onto the powder.
• Gently swirl or roll the vial until everything has dissolved. Do not shake: foam can damage peptides.
• Check the solution: it should be clear, without particles or cloudiness.
• Write the date, the concentration, the solvent and the lot number on the vial.

The concentration is the amount of peptide divided by the volume of solvent. Dissolve 10 mg in 2 ml and the concentration is 5 mg/ml, or 5000 µg/ml. More solvent gives a lower concentration, but not more material.

The peptide calculator works this out quickly, also in µg/ml. Use the net amount in mg as stated on the label and the certificate.

• Put the solution in the fridge (2–8 °C) straight away, on an inner shelf and not in the door, where the temperature changes every time it opens.
• Do not freeze a solution: ice crystals can damage the peptide structure.
• Use a solution in bac water within about 28 days. Use a solution in sterile water without preservative in one go.
• Keep the vial upright and protected from light. Does the solution turn cloudy or yellow, or do you see particles? Then stop using it.

• Shaking instead of swirling, which creates foam.
• Aiming the solvent straight at the powder instead of letting it run down the wall.
• Opening a cold vial, so moisture gets in.
• Freezing a dissolved vial.
• Using a vial of sterile water without preservative over several days.

How long does dissolving take?

Usually the powder has dissolved after a few minutes of gentle swirling. If something remains, let the vial stand for a while and swirl again. If it still does not dissolve, check the data sheet to see whether another solvent fits.

There is foam on the solution. What now?

Let the vial stand upright in the fridge until the foam has gone, and swirl rather than shake from now on.

Can a dissolved vial go in the freezer?

No. Ice crystals can damage the peptide structure. Keep a solution in the fridge (2–8 °C).

Bac water or acetic acid water?

For most peptides, bac water. Acetic acid water is for peptides that dissolve poorly at neutral pH; the data sheet or certificate tells you which solvent fits.

• View Bac water in the shop
• View Acetic acid water in the shop