GHK-Cu is unusual among research peptides because you can see something about it before any instrument is involved: it is blue. That colour, and the copper behind it, shapes how the compound is documented, dissolved and stored. This is a laboratory handling guide for material supplied for in vitro research use.
What GHK-Cu is
GHK is a tripeptide: glycine, histidine and lysine, in that order. On its own it is a small, colourless molecule of about 340 Da. GHK-Cu is the same tripeptide bound to a copper(II) ion, which brings the mass to roughly 402 Da for the one-to-one complex. The histidine side chain and the peptide backbone hold the copper, and that coordination is what gives the complex its blue colour.
Reading the certificate
A few points are specific to a metal complex:
- Check which form the certificate describes. GHK and GHK-Cu are different materials with different masses, and the name on the certificate should match the name on the label.
- Purity by HPLC describes the peptide. Some certificates also report copper content separately, which tells you how much of the peptide is actually in complexed form.
- The appearance line should say blue or blue-violet powder. A white powder labelled GHK-Cu deserves a question.
- As with any peptide, the batch number on the vial should match the batch number on the certificate.
Dissolving it
GHK-Cu dissolves readily in water and aqueous buffers, giving a clear blue solution whose depth of colour follows the concentration. Because the copper is held by coordination rather than a covalent bond, strongly acidic conditions and strong chelators such as EDTA can pull it away from the peptide. If your buffer contains a chelator, expect the complex to be affected and plan the experiment around that.
Storage and what colour tells you
Store according to the batch label. In general the dry powder is kept cold, sealed and protected from light, and solutions are kept refrigerated and used within a short, documented window. A solution that changes from clear blue to cloudy, or loses its colour, has changed chemically and should not be relied on. Note the colour and clarity in your records when you prepare a solution: for this compound it is a quick, free observation.