Semax (Met-Glu-His-Phe-Pro-Gly-Pro): preparation and storage

What the research context means

After permanent middle cerebral artery occlusion in rats, Semax and PGP alone altered transcription of neurotrophins and their receptors with partly different profiles [1]. For laboratory work, a degradation mixture therefore cannot be assumed equivalent to intact Semax. A biological signal need not disappear at the same point as partial loss of the parent peptide.

For gene-expression experiments, record the interval from addition to RNA collection. Avoid comparing fresh and long-held stock without checking chromatographic composition. Results following animal exposure do not establish chemical stability of an aqueous stock or prepared cell mixture.

Solvent and final matrix

Choose the solvent for the actual Semax form and final system. Do not copy a finished nasal product into cell culture: excipients, pH and microbiological requirements differ. Water is a possible starting matrix only where batch solubility supports it; saline and culture medium need separate checks.

The sequence contains methionine. Its oxidation is a relevant analytical risk to investigate, rather than evidence that every Semax stock oxidises rapidly. In LC-MS, a peak with a mass increase near +16 Da can be consistent with addition of one oxygen atom; the modification site needs confirmation. Avoid adding an antioxidant to all samples without controlling for its effect on the experiment.

Laboratory calculation example

Bringing 0.81392 mg of pure unmodified Semax to a final 1.000 mL gives a calculated 1.000 mmol/L. Diluting 10.0 µL of that stock to a final 1.000 mL gives 10.0 µmol/L. This illustrates the calculation rather than selecting an experimental concentration. Such precision is unjustified for a nominal 5 mg vial with unknown peptide content.

Across a concentration series, match the final solvent amount rather than only the volume of peptide added. Acid or DMSO in a stock is diluted too and may change the final matrix. The peptide-free control receives the same matrix.

Quality checks during handling

If a new peak appears with increased mass, investigate oxidative modification rather than treating it as an ordinary concentration change. Quantitation requires separation of parent Semax from the modified form. If only the main peak intensity changes without new components, check quantitative transfer and sample volume. These are different questions that one visual inspection cannot resolve.

For a transcription experiment, prepare a separate cell-free analytical sample with matching matrix, temperature and duration. It shows reagent behaviour in medium, although it does not reproduce cellular uptake or enzymatic processes. If the cell response persists while intact Semax declines, examine mixture composition; the PGP results in the cited paper explain why a functional test alone is insufficient.

In result tables, identify “Semax, unmodified form” and the LOT. Use a separate series for an acetylated analogue. Matching nominal mass may still mean different molecule counts and chemical properties. Combining those series hides a reagent difference before statistical analysis begins.

Dry material and solution need separate conditions

For long-term storage of a dry synthetic peptide, use a freezer, commonly −20 °C or below, where the specification supports it. Allow the sealed vial to reach room temperature before opening so moisture does not condense on cold powder. A refrigerator at +2–8 °C can be a working option for dry material needed within a week or a month only when the supplier supports that interval. Planning to use a vial soon does not establish its shelf life.

A solution needs its own record: solvent, concentration, pH, preparation date, temperature and permitted holding time. Do not transfer the dry-material expiry to the solution. Where freezing is supported, prepare aliquots for individual experiments; thawing the remainder again needs separate validation. Bacteriostatic water contains a preservative that can change a cell-assay result and is not a default solvent for every peptide.

Practical questions

Can Semax be checked through biological activity alone? No. Related PGP also showed activity in the cited work, so analytical measurement of the parent peptide is needed. Can heating dissolve a residue? Only under a procedure that checks chemical integrity; clarity after heating does not establish it.

Does this page cover acetylated or amidated analogues? Only its general recording and validation principles apply. Molecular weight, solubility and storage life are determined separately for each form.

Monograph · Product page · Certificates of analysis

General reagent preparation · Bacteriostatic water compatibility · Storage and expiry

Sources

1. Dmitrieva Veronika G., Povarova Oksana V., Skvortsova Veronika I., Limborska Svetlana A.. Semax and Pro-Gly-Pro Activate the Transcription of Neurotrophins and Their Receptor Genes after Cerebral Ischemia. 2009.

MedChemExpress: semax. Reference characteristics of that catalogue material; not a specification for a Longeva batch.

Bachem: General peptide handling principles