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Why GHK-Cu is blue: copper peptide chemistry
What GHK-Cu is, how the GHK tripeptide binds copper, why the complex is blue, and how it was first identified.
A tripeptide and a copper ion
GHK is a tripeptide: glycine, histidine and lysine. GHK-Cu is the complex it forms with a copper(II) ion. GHK binds copper very tightly, mainly through nitrogen atoms from the glycine and the histidine and from the peptide backbone between them.
Why it's blue
Copper(II) complexes are often blue because of how the copper ion's electrons absorb light. In GHK-Cu, the arrangement of the binding atoms around the copper means the complex absorbs light at the orange-red end of the spectrum, so what we see is the blue that's left. Plain GHK, without copper, is a white powder.
How it was found
GHK was identified in 1973 by Loren Pickart, who isolated it from the albumin fraction of human plasma while studying why plasma from younger people made liver tissue from older people behave more like younger tissue. Its strong affinity for copper was reported in later work, in the late 1970s and 1980.
In the lab
GHK-Cu has since been studied in cell culture and animal models of skin and connective-tissue biology, and is widely used in cosmetic ingredient research. Lyophilised GHK-Cu is usually stored sealed at −20 °C for the long term, away from light; some suppliers give 2–8 °C for short-term storage.
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