What the molecule is
Semax is a synthetic heptapeptide with the sequence MEHFPGP and an average mass near 813.9 daltons, supplied as a lyophilised powder, acetate salt.
It is built from a short fragment of adrenocorticotropic hormone, the pituitary peptide usually abbreviated ACTH. The first four residues of Semax correspond to residues four to seven of that hormone, methionine glutamate histidine phenylalanine. Like Selank, it carries a proline glycine proline extension at the carboxyl terminus.
The design follows a line of research opened by David de Wied and colleagues from the 1960s onward, who showed that fragments of adrenocorticotropic hormone too short to carry the hormone's endocrine activity nevertheless remained active in behavioural assays in rodents. That separation, between the endocrine function of the whole hormone and the activity of short fragments, is what made fragment analogues an interesting class to work on. Semax was developed at the Institute of Molecular Genetics of the Russian Academy of Sciences.
Published research context
Published research on Semax largely concerns rodent models and cultured neural cells. Reported research areas include gene expression profiling in brain tissue, studies of neurotrophic factor expression in culture, and work on peptide stability and fragmentation.
As with Selank, a large share of the primary literature is Russian and a meaningful part of it is published in Russian language journals, so the accessible English record understates the total volume of work. Anyone planning experiments in this area should expect to spend time on literature access.
One structural point recurs in the literature and is worth stating. The parent hormone, adrenocorticotropic hormone, is thirty nine residues long and has a well defined endocrine function mediated by the melanocortin receptors. A four residue fragment cannot engage those receptors in the same way, so work on fragment analogues is not work on the parent hormone, and results from one do not carry over to the other. Papers on this class generally make the distinction explicitly.
The published work describes rodent and cell culture systems. This material is supplied for laboratory research only and not for any use involving people.
How each lot is characterised
Purity is measured by reversed phase high performance liquid chromatography with ultraviolet detection at 214 nanometres and reported as main peak area over total integrated area. Identity is confirmed by electrospray ionisation mass spectrometry against the theoretical mass.
Two features of the sequence are analytically relevant. The amino terminal methionine is readily oxidised to the sulfoxide, which adds sixteen daltons and generally produces an earlier eluting peak, so both the chromatogram and the mass spectrum report on the oxidation state of a lot. The two proline residues can produce the conformer related peak broadening described for other proline containing peptides, which is a chromatographic artefact rather than an impurity.
The certificate records appearance, purity, identity, net peptide content, water content and counter ion, published against the lot number on the vial label.
Handling on the bench
Store the unopened vial at minus twenty degrees, dark and desiccated. As with any methionine containing peptide, limiting exposure to light and to air is worth the small amount of extra care, because methionine oxidation is the most likely slow degradation route for this molecule.
Bring the vial to room temperature before opening. Reconstitute with bacteriostatic water added slowly against the vial wall, swirling rather than shaking.
Refrigerate after reconstitution and aliquot for single use. Minimising headspace in storage tubes reduces available oxygen. Avoid repeated freeze and thaw cycles, and where a lot has been held in solution for a period, a quick reanalysis before a critical experiment will show whether an oxidation shoulder has appeared.
Specification
| Form | Lyophilised powder, acetate salt |
|---|---|
| Sequence | MEHFPGP |
| Residues | 7 |
| Average mass | 813.9 Da |
| Fill size | 10 mg |
| Storage | Minus 20 degrees, dark and desiccated |
References
- de Wied D (1997). Neuropeptides in learning and memory processes. Behavioural Brain Research, volume 83.
For research use only
Products are supplied for laboratory research by qualified researchers and institutions. They are not for human or veterinary use, not for diagnostic or therapeutic use, and are not drugs, foods or cosmetics.