How the material
is made and measured.
A working reference for the people actually running the bench: how these compounds are synthesised, what each release assay does and does not tell you, and how to store and reconstitute material without quietly degrading it.
What a peptide
actually is.
A peptide is a short chain of amino acids joined by amide (peptide) bonds. The only formal difference between a peptide and a protein is length: chains up to roughly fifty residues are conventionally called peptides, longer ones proteins. Everything in this catalogue sits between three and forty-three residues, which is why it can be built synthetically rather than expressed in cells.
Sequence is identity. Reorder two residues and you have a different molecule with a different shape, a different receptor fit, and different stability — even though the mass on the spectrometer is unchanged. That is why identity testing and purity testing are separate questions, and why a certificate that reports only purity is incomplete.
Biologically, peptides act as signalling molecules: they bind receptors, act as fragments of larger regulatory proteins, or mimic endogenous hormones. Because they are chains of natural building blocks, they are also degraded quickly by peptidases, which is a large part of why so much research work goes into analogues, substitutions and blocking groups.
Everything below is a description of the published research literature. Nothing here is medical advice, a dosing recommendation, or a claim of safety or efficacy in humans. All material is sold for laboratory research use only.
Residues
Each amino acid in the chain is one residue. Residue count is the plainest proxy for how hard a compound is to synthesise cleanly.
Sequence
The order of residues, written N-terminus to C-terminus. It determines fold, receptor binding and degradation route.
Modifications
Acetylation, amidation, cyclisation, D-amino acids or a fatty-acid chain, added to slow enzymatic breakdown.
Salt form
Peptides are isolated as a salt — usually acetate or trifluoroacetate — which is part of the vial mass but not the peptide.
What each compound is,
and what the literature studies.
Structural and pharmacological description of each compound we carry, with a published reference for each. Descriptions summarise what a molecule is and what it has been investigated for in preclinical or clinical literature — they are not directions for use.
No compound matches that search.
Regulatory peptides
BPC-157
A synthetic pentadecapeptide derived from a sequence found in human gastric juice. Preclinical literature examines it in models of tendon, muscle, gut and nerve repair, with proposed mechanisms centring on angiogenesis and growth-factor signalling.
View sourceTB-500 / Thymosin β4
The synthetic form of thymosin beta-4, an actin-sequestering peptide. Studied in cell migration, angiogenesis and cardiac and corneal repair models.
View sourceThymosin alpha-1
A thymus-derived immunomodulatory peptide, investigated in the literature for effects on T-cell maturation and innate immune signalling.
View sourceKPV
The C-terminal tripeptide of alpha-MSH. Studied for anti-inflammatory signalling in intestinal epithelium and NF-κB pathway models.
View sourceLL-37
The only human cathelicidin-derived antimicrobial peptide. Extensively studied for membrane-disrupting antimicrobial activity and immunomodulation.
View sourceARA-290 (cibinetide)
A non-erythropoietic peptide derived from the tissue-protective face of erythropoietin. Investigated in ischemia/reperfusion and small-fibre neuropathy research.
View sourceAOD-9604
A modified fragment of the C-terminus of human growth hormone, studied in lipolysis and adipose metabolism models without the growth-promoting activity of full-length hGH.
View sourceVIP
An endogenous neuropeptide acting at VPAC1/VPAC2 receptors, studied for vasodilatory, secretory and immunoregulatory signalling.
View sourceIncretin analogs
Semaglutide
A fatty-acid-acylated GLP-1 analogue with substitutions that resist DPP-4 cleavage, giving a long half-life. Studied extensively for glycaemic and body-weight endpoints.
View sourceTirzepatide
A single peptide acting at both the GIP and GLP-1 receptors, studied in metabolic and weight-regulation trials.
View sourceRetatrutide
A triple-receptor agonist adding glucagon-receptor activity to the incretin pair, reported in phase-2 obesity literature.
View sourceLiraglutide
An acylated GLP-1 analogue with a shorter duration than semaglutide; one of the most characterised molecules in the incretin class.
View sourceCagrilintide
A long-acting amylin receptor agonist, studied alone and in combination with GLP-1 agonists for satiety signalling.
View sourceSurvodutide
A dual glucagon and GLP-1 receptor agonist investigated in obesity and metabolic-liver-disease research.
View sourceGHRH-class analogs and secretagogues
CJC-1295 (with and without DAC)
A modified GHRH fragment; the DAC version carries a drug-affinity complex that binds albumin and extends circulating half-life. Studied for pulsatile GH release.
View sourceSermorelin
The shortest fully active fragment of growth-hormone-releasing hormone, long used as a research probe of pituitary GH responsiveness.
View sourceTesamorelin
A trans-3-hexenoyl-modified GHRH analogue with improved stability; studied for effects on visceral adipose tissue and the GH/IGF-1 axis.
View sourceIpamorelin
A selective GHS-R1a agonist noted in the literature for releasing GH with little effect on cortisol or prolactin, unlike earlier GHRPs.
View sourceGHRP-2 and GHRP-6
Synthetic hexapeptide secretagogues acting at the ghrelin receptor. GHRP-6 is the more strongly appetite-stimulating of the pair in animal models.
View sourceHexarelin
A potent hexapeptide secretagogue also studied for cardiac effects mediated through CD36 independently of GH release.
View sourceNeuropeptides
Semax
A heptapeptide analogue of ACTH(4-10) without corticotropic activity. Russian and international literature examines BDNF/TrkB expression and neuroprotection models.
View sourceSelank
A synthetic analogue of the immunomodulatory peptide tuftsin, studied for anxiolytic-like activity in animal models.
View sourceDihexa
An oligopeptide-derived HGF/c-Met potentiator studied for synaptogenesis in cognition models.
View sourceCerebrolysin
A porcine-brain-derived mixture of low-molecular-weight peptides and amino acids studied in stroke and neurodegeneration literature.
View sourceP21
A small peptidomimetic derived from ciliary neurotrophic factor, studied for neurogenesis and tau-related endpoints in rodent models.
View sourcePE-22-28
A truncated spadin analogue acting as a TREK-1 channel blocker, examined in antidepressant-like behavioural research.
View sourceCopper complexes
GHK-Cu
Glycyl-L-histidyl-L-lysine complexed with copper(II). Literature covers wound-repair signalling, collagen and gene-expression modulation in fibroblast models.
View sourceAHK-Cu
Alanyl-histidyl-lysine copper complex, studied alongside GHK-Cu for angiogenic and dermal-papilla effects in vitro.
View sourceMitochondrial compounds
MOTS-c
Encoded in mitochondrial DNA rather than the nuclear genome. Studied for AMPK signalling, metabolic homeostasis and longevity association.
View sourceHumanin
The first identified mitochondrial-derived peptide, studied for cytoprotective signalling in neuronal and metabolic models.
View sourceSS-31 (elamipretide)
A mitochondria-targeting tetrapeptide that binds cardiolipin in the inner membrane; studied for effects on electron-transport efficiency and ROS.
View sourceNAD+
Nicotinamide adenine dinucleotide, the redox coenzyme central to metabolism and to sirtuin and PARP activity. Included as a research reagent, not a peptide.
View sourceNeuroendocrine peptides
Kisspeptin-10
The active decapeptide fragment of kisspeptin, an upstream regulator of GnRH release and a central tool in reproductive-axis research.
View sourceGonadorelin (GnRH)
Synthetic gonadotropin-releasing hormone, used in research to probe pituitary LH and FSH responsiveness.
View sourceMelanotan II
A cyclic non-selective melanocortin receptor agonist, studied for melanogenesis and MC4R-mediated behaviour in animal models.
View sourcePT-141 (bremelanotide)
A metabolite of melanotan II with greater melanocortin-4 selectivity; studied for central effects on sexual-behaviour pathways.
View sourceOxytocin
An endogenous hypothalamic nonapeptide with a disulfide bridge, studied for uterine and social-behaviour signalling through OXTR.
View sourceBlends
KLOW Blend
A combined preparation of GHK-Cu, KPV, BPC-157 and TB-500. Each component has its own literature; the blend itself has none, and is released on identity and purity of the mixture.
View sourcesReferences are provided for research and educational purposes. Valence Bios makes no representation regarding safety or efficacy in humans. All products are sold for laboratory research use only.
Solid-phase, one block at a time.
Peptides are assembled by solid-phase peptide synthesis (SPPS). The C-terminal residue is anchored to a resin bead, then each subsequent amino acid is coupled on in turn: deprotect the growing chain, couple the next Fmoc-protected residue, wash, repeat. A forty-residue chain is roughly forty of those cycles.
Every cycle is imperfect. A coupling that runs at 99.5% efficiency still leaves a fraction of chains one residue short, and those deletion sequences accumulate multiplicatively with length. That is precisely why chain length correlates with how hard a compound is to make cleanly, and why purity claims on long chains deserve more scepticism than purity claims on a tripeptide.
After the final cycle the chain is cleaved from the resin, the side-chain protecting groups are removed, and the crude material is purified by preparative reverse-phase HPLC. It is then lyophilised under controlled conditions into the white cake you receive, and sealed under inert headspace.
Resin loading
The C-terminal residue is anchored to the solid support that holds the chain through every subsequent cycle.
Coupling cycles
Deprotect, couple, wash. Repeated once per residue, with the reaction monitored at each step.
Cleavage & purification
The chain is cleaved and side-chain deprotected, then purified by preparative reverse-phase HPLC.
Lyophilisation
Freeze-dried into a stable cake, sealed, and held in cold storage pending third-party release testing.
What each test
can and cannot tell you.
RP-HPLC
Answers: what fraction of the material is the main species. Does not answer: whether that species is the molecule you ordered. A pure batch of the wrong sequence still reads 99%.
ESI mass spectrometry
Answers: whether the observed molecular mass matches the theoretical mass of the declared sequence. Does not answer: ordering of isobaric residues, which needs sequencing.
LAL endotoxin
Answers: bacterial endotoxin burden in EU/mg. Matters for: anything touching cell culture, where endotoxin confounds results long before it is visible.
Karl Fischer
Answers: residual water in the lyophilised cake. Matters for: mass accuracy when you weigh, and how quickly the material degrades in storage.
Peptide content
Answers: how much of the vial mass is actually peptide versus counter-ion and water. A 10mg vial at 80% content is 8mg of peptide.
Appearance & solubility
Answers: whether the cake and the reconstituted solution look as they should. Cloudiness or a coloured solution is a reason to stop.
What has to be true
before a lot ships.
| Attribute | Method | Specification |
|---|---|---|
| Purity | RP-HPLC, UV 214nm | ≥ 99.0% main peak |
| Identity | ESI-MS | Observed mass conforms to theoretical |
| Endotoxin | LAL, kinetic chromogenic | < 0.10 EU/mg |
| Water content | Karl Fischer | ≤ 8.0% |
| Appearance | Visual | White to off-white lyophilised cake |
| Solubility | Visual, post-reconstitution | Clear, colourless, no particulates |
| Traceability | Documentation | Lot on vial resolves to a published certificate |
Anything failing a line of this table is held for secondary review rather than released. Lab consumables are certified against USP conformance instead, since there is no chain to assay.
Most degradation happens
after delivery.
Lyophilised material is comparatively robust; reconstituted material is not. Bring the vial to room temperature before opening so condensation does not form on the cake, add solvent slowly down the vial wall rather than directly onto the powder, and swirl instead of shaking — foaming denatures peptide at the air-liquid interface.
| State | Temperature | Working window | Notes |
|---|---|---|---|
| Lyophilised, sealed | -20 °C | 24 months | Protect from light and moisture |
| Lyophilised, sealed | 2–8 °C | Up to 3 months | Acceptable for material in active use |
| Lyophilised, in transit | Ambient, cold-packed | Days | Short excursions are tolerated |
| Reconstituted | 2–8 °C | 2–4 weeks | Bacteriostatic water; compound dependent |
| Reconstituted, aliquoted | -20 °C | Months | Avoid repeated freeze-thaw; aliquot first |
What actually degrades a chain.
Oxidation
Methionine, cysteine and tryptophan residues oxidise on exposure to air and light. Inert headspace and amber storage slow it down.
Hydrolysis
Asp-Pro and Asp-Gly bonds are the usual first failures, accelerated by moisture and by pH drift away from neutral.
Deamidation
Asparagine and glutamine convert over time, shifting mass by roughly 1 Da — visible on MS long before it is visible on a chromatogram.
Aggregation
Driven by freeze-thaw cycling and by shaking. Aliquot once, then leave the aliquots alone.
Adsorption
Dilute solutions lose material to glass and plastic surfaces. At low concentrations this is a real source of assay drift.
Freeze-thaw
Each cycle costs a measurable fraction of intact chain. Plan aliquot volumes around a single use.
Terms that appear
on our certificates.
Purity vs. peptide content
Purity is the proportion of the material that is the main chromatographic species. Peptide content is how much of the vial mass is peptide rather than counter-ion (usually trifluoroacetate or acetate) and residual water. A vial can be 99% pure and still be 80% peptide content by mass.
EU/mg
Endotoxin units per milligram of peptide, from the LAL assay. Lower is better; sub-0.10 EU/mg is the threshold we release against.
Theoretical vs. observed mass
The theoretical mass is calculated from the declared sequence. The observed mass comes off the mass spectrometer. Identity is confirmed when the two agree within instrument tolerance.
Deletion sequence
A chain missing one or more residues because a coupling cycle did not go to completion. Deletion sequences are the main impurity class in SPPS material and the main thing HPLC is separating out.
Counter-ion
The salt form the peptide is isolated as. TFA is common from preparative HPLC; acetate is preferred for cell work because TFA is cytotoxic at higher concentrations.
Retest date
The date by which a stored lot should be re-analysed rather than assumed to still meet specification. It is not an expiry in the pharmaceutical sense.
Where to check us.
- Merrifield, R. B. (1963) Solid phase peptide synthesis I: the synthesis of a tetrapeptide. J. Am. Chem. Soc. — the original SPPS method every modern synthesis descends from.
- Manning, M. C. et al. (2010) Stability of protein pharmaceuticals: an update. Pharm. Res. — the standard reference on oxidation, deamidation and aggregation pathways.
- United States Pharmacopeia <85> Bacterial Endotoxins Test — the LAL methodology our endotoxin numbers are generated against.
- ICH Q1A(R2) Stability testing of new drug substances and products — the framework behind our storage and retest windows.
- ICH Q2(R2) Validation of analytical procedures — how the HPLC and MS methods used on your batch are validated.