What is Testagen?
The sequence recorded in our molecular dataset is H-Lys-Glu-Asp-Gly-OH, four residues. No CAS registry number, formula or molecular weight is assigned there, so none is quoted. Structurally the peptide is the KED tripeptide of Vesugen with a glycine appended, which places the two in the same design lineage. The lysine and two acidic residues make the molecule zwitterionic and very water soluble.
The family originates with Vladimir Khavinson and colleagues at the St Petersburg Institute of Bioregulation and Gerontology, whose programme moved from cytomedines, peptide fractions of animal organs, to cytogens, the shortest synthetic sequences that reproduced activity in their assays. The proposed mechanism is that di-, tri- and tetrapeptides enter cell nuclei and bind promoter-region DNA or histone proteins, altering transcription of genes tied to the source tissue.
That mechanism is a hypothesis rather than a settled finding. Supporting data come mainly from docking simulations and spectroscopic binding studies published by the originating group, no structural biology has confirmed a sequence-specific complex, and independent replication of tissue-specific transcriptional effects is limited. What is established is the chemical identity of the tetrapeptide and its behaviour as a stable, highly soluble small peptide.
Reconstitution & handling
The powder dissolves rapidly in bacteriostatic or sterile water added slowly down the vial wall, since a charged four-residue peptide is freely water soluble. Concentration is the labeled milligram content divided by the diluent volume added, reported as mass per millilitre rather than molarity because no molecular weight is assigned in our dataset. Gentle swirling is sufficient, and the solution should be clear and colorless.
Storage & stability
Sealed vials are held at -20 degrees Celsius, protected from light and atmospheric moisture, since the cake is hygroscopic. Reconstituted material is refrigerated at 2 to 8 degrees Celsius, divided into single-use aliquots, and kept away from repeated freeze-thaw cycles. The sequence has no cysteine, methionine or tryptophan, so oxidation is not a significant liability, and slow backbone hydrolysis sets the limit on solution shelf life.
How it's tested
Purity is determined by reverse-phase HPLC at 214 and 220 nanometres, since no aromatic residue is present to absorb at 280 nanometres, and short polar peptides of this kind usually need an ion-pairing agent for adequate retention. Identity is confirmed by mass spectrometry against the theoretical mass calculated from the sequence. Net peptide content is measured so the labeled figure reflects peptide rather than counter-ion and water.