Reconstituting Lyophilised Proteins: A Practical Bench Protocol

Updated 2026-09-28

A short, practical protocol for bringing lyophilised proteins back into solution without losing activity.

Before you open the vial

Spin the vial briefly in a microcentrifuge so that powder adhering to the cap is collected, and let the vial reach room temperature to avoid condensation on the powder.

Choosing the diluent

Use the buffer recommended on the CoA. If none is given, a neutral buffer such as PBS is usually safe; only add carrier protein (for example BSA) if your assay is compatible with it, since carriers can interfere with calibrators.

Adding the liquid and storing

Add the diluent down the wall of the vial, never directly onto the powder, and mix by gentle inversion rather than vortexing. Prepare single-use aliquots before freezing to avoid repeated freeze–thaw cycles, and record the lot number on every aliquot.

Getting the concentration right after reconstitution

The concentration on the label describes the material before lyophilisation. The volume you add is your own decision, which means the concentration in your vial is yours to get right or wrong. Two errors are common. The first is adding a volume that leaves the protein so dilute that each aliquot carries a large relative pipetting error, which propagates silently into every downstream result. The second is forgetting that the powder occupies volume, which matters at high protein loads and pushes the true concentration above the nominal figure. For most laboratory work that second error is small compared with pipetting error, but it is worth knowing that the nominal concentration is a target rather than a measurement. Where the concentration genuinely matters — preparing calibrators, for instance — confirm it in your own system instead of assuming it transferred intact through reconstitution.

When lyophilised is the wrong choice

Lyophilisation is a trade rather than an upgrade. It buys ambient shipping and freezer-free storage at the cost of a reconstitution step that can go wrong, and of a drying process that can perturb a labile conformation. For a calibrator that has to be gravimetrically exact, or for a protein whose activity depends on a delicate fold, a frozen liquid preparation is often the better choice even though it demands dry-ice logistics and a working freezer at the other end. It is also worth asking what the lyophilised cake contains, because the format name says nothing about the formulation. A preparation bulked with a carrier protein is unsuitable as a calibrator antigen while being perfectly fine for immunisation; a carrier-free lyophilised preparation can serve both. Ask for the formulation, not just the format.

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