Peptide reconstitution calculator

How the peptide calculator works

When you add a diluent such as bacteriostatic water to a vial of lyophilised peptide, the peptide dissolves evenly into that volume. The calculator uses three numbers:

• Peptide in the vial – the labelled mass, e.g. 10 mg.
• Diluent added – the volume of liquid you add, e.g. 2 mL.
• Target mass per aliquot – the amount of peptide you want in each portion for your experiment, in micrograms.

The formulas

Concentration (mg/mL) = peptide mass (mg) ÷ diluent volume (mL). Because 1 mg/mL equals 1 µg/µL, the volume that holds your target mass is simply target mass (µg) ÷ concentration (mg/mL), giving the answer in microlitres.

Worked example

A 10 mg vial reconstituted with 2 mL gives 5 mg/mL (5 µg/µL). A 250 µg aliquot therefore needs 50 µL, and the vial holds 40 such aliquots.

Choosing the volume of diluent

More diluent gives a lower concentration and larger volumes per aliquot, which can make small amounts easier to measure accurately with a micropipette. Less diluent gives a more concentrated solution. Most 3 ml vials hold up to about 3 mL comfortably.

For a step-by-step method, read our guide to reconstituting peptides with bacteriostatic water, and see the peptide stability and pH guide for compounds that need an acidic diluent.