Peptide Complexes

A coordination complex is formed when donor atoms on a molecule bind a metal ion. In a peptide complex the donors are typically backbone nitrogens and side-chain groups — imidazole nitrogen on histidine, for instance — and the resulting species has a defined stoichiometry, a defined formula and a molecular weight that includes the metal.

This is why a complex is listed separately from its parent sequence rather than as a variant of it. The two have different formulae, different masses, different solubility behaviour and, frequently, different colour. Ordering one where the other is required is a substitution, not a preference.

Metal complexes are often coloured, and the colour is intrinsic to the compound rather than an impurity or a defect. A copper(II) tripeptide complex, for example, is characteristically blue — a vial of blue solid is the expected observation and a colourless one would be the anomaly.

Because appearance carries real information for this class, it is recorded as a specification field on every listing here rather than being left for the researcher to infer from a photograph.

Complexes are supplied lyophilized and stored at freezer temperature, protected from light and moisture, with the vial allowed to equilibrate to ambient temperature before opening.

Coordination equilibria are sensitive to pH and to competing ligands, and buffer components can compete for the metal. Where the identity of the complex matters to the work, buffer composition is a variable to control rather than a detail to inherit from an existing protocol.

Materials in this category are supplied for laboratory research applications only. They are not intended for human or veterinary use, consumption, diagnosis, treatment, cure or prevention of disease. No listing on this site describes a use, a dose, a route of administration or an outcome, and support answers questions on identity, specification and analytical documentation only.

Ordering requires a verified research account and acceptance of the research use agreement. Specifications and prices are readable without one.