Reconstitution
Reconstitution turns a freeze-dried peptide into a measurable liquid. There is one idea worth internalising: the peptide mass in the vial is fixed, the volume of water you add is what sets the concentration.
What reconstitution is
A research peptide ships lyophilised, freeze-dried into a small cake or film at the bottom of the vial. In that dry state it is stable and easy to transport, but it cannot be measured by volume. Reconstitution is the step that dissolves that solid back into a liquid of known concentration, so a defined volume corresponds to a defined mass.
You do this by introducing a measured amount of a suitable diluent, usually bacteriostatic or sterile water, into the vial and letting the peptide go fully into solution.
The one idea that matters
The amount of peptide in the vial never changes. A 5 mg vial holds 5 mg of peptide whether you add 1 mL of water or 5 mL. What does change is the concentration, and that is entirely your choice, set by how much water you add.
Mass is fixed, concentration is chosen
Add less water for a more concentrated solution, more water for a more dilute one. The same 5 mg vial becomes 5 mg/mL with 1 mL of water, or 2.5 mg/mL with 2 mL. The full arithmetic lives on the concentration page.
How to add the water
The peptide bond is delicate, so the water goes in gently. Aim the stream down the inside glass wall of the vial rather than blasting it directly onto the peptide cake, add it slowly, and then let the solid dissolve on its own or with a gentle swirl.
Aim down the glass wall
Let the measured water run down the inner side of the vial, not straight onto the peptide. This protects the fragile peptide from the force of the stream.
Add slowly
Introduce the water gradually rather than all at once, so the solid is wetted evenly and dissolves without being agitated.
Swirl, never shake
If anything needs encouraging, swirl the vial gently or let it stand. Shaking foams the solution and stresses the peptide.
Swirl, don't shake
Most peptides go into solution with little or no help. Give one a minute to dissolve on its own before swirling. Never shake a reconstituted vial, agitation and foaming can degrade the peptide.
Next steps
With the idea in hand, the two decisions in front of you are which water to use and how much to add for the concentration you want.