A summary of published research, with citations. It states no amount, schedule or route, and makes no claim about what this compound does in a person. Supplied for laboratory research use only.
Most of the confusion in this field is vocabulary. Purity, potency and content sound interchangeable and are three unrelated measurements; affinity and efficacy are routinely swapped; "approved" means something much narrower than it reads. These are the terms that turn up in papers, on certificates of analysis and on regulatory pages, defined plainly. Defining a word instructs nobody in anything. Nothing here is medical, dosing, or therapeutic guidance.
Chemistry and structure
| Term | Definition |
|---|---|
| Amino acid | The building block of a peptide. Around twenty are used to build proteins in humans, each with the same backbone and a distinct side chain that determines charge, size and hydrophobicity. |
| Residue | A single amino acid once it is part of a chain. A fifteen-residue peptide is fifteen amino acids joined in a fixed order by amide bonds. |
| Sequence | The ordered list of residues that defines a peptide, written from the amino end to the carboxyl end. The sequence is the molecule; reversing it gives a different compound. |
| N-terminus and C-terminus | The two ends of the chain, carrying the free amino and free carboxyl group respectively. Modifications are often made at one or both, because the termini are where proteases most readily attack. |
| Analogue | A peptide deliberately altered from a natural sequence, by substituting a residue or attaching a chemical group, usually to slow degradation or change which receptors it engages. |
| Fragment | A short piece of a longer natural peptide or protein. Being a fragment says where a sequence came from, and nothing about whether it behaves like the parent. |
| Molecular weight | The mass of one molecule, in daltons. It is the figure mass spectrometry checks a synthesised peptide against, and a mismatch means the vial does not hold the intended compound. |
Synthesis, handling and analysis
| Term | Definition |
|---|---|
| Solid-phase peptide synthesis | The standard manufacturing method: the chain is built one residue at a time while anchored to an insoluble resin bead, so excess reagents can be washed away between cycles. |
| Truncated sequence | A chain that stopped short because a coupling step failed. Chemically similar to the target, it is the impurity hardest to separate and the one a purity figure is likeliest to hide. |
| Counter-ion | A salt left over from purification, commonly trifluoroacetate or acetate, still bound to the peptide after drying. It adds mass to the vial without being peptide. |
| Lyophilisation | Freeze-drying under vacuum, removing water by sublimation and leaving a dry cake. Dry peptide is far more stable than dissolved peptide, which is why material ships in this form. |
| Reconstitution | Dissolving the cake in a diluent to give a solution of known concentration. The arithmetic is division: 10 mg of peptide in 2 mL of diluent gives 5 mg/mL. |
| Bacteriostatic water | Sterile water containing a small percentage of benzyl alcohol, which inhibits bacterial growth in a solution that will be stored rather than used at once. A laboratory diluent, not a therapeutic product. |
| Chromatographic purity | The proportion of a sample resolving as the target peptide on an HPLC trace. It describes one batch at one moment and says nothing about identity, or about how much peptide the vial holds by weight. |
| Net peptide content | The mass of actual peptide in a vial, separate from counter-ions and residual water, measured by a quantitative assay. A chromatographically clean vial can still be underweight. |
| HPLC | High-performance liquid chromatography, which separates a mixture by passing it through a packed column. The trace it produces is what a purity percentage is calculated from, and reading the trace shows where the impurities sit. |
| Mass spectrometry | Measurement of mass-to-charge ratio, used to confirm the compound present is the one intended. Purity answers "how much of one thing"; mass spec answers "which thing". |
| Endotoxin | Lipopolysaccharide from bacterial cell walls, reported in endotoxin units per milligram. Biologically active at trace levels and invisible to a purity figure, which makes it the test most worth insisting on for animal work. |
| Certificate of analysis | A laboratory report on one batch, identified by lot number. It covers what was tested on the date of testing, and concerns the vial in your hand only if the lot numbers match. |
Pharmacology
| Term | Definition |
|---|---|
| Receptor and ligand | A receptor is a protein that binds a signalling molecule and converts the binding into a cellular response. The molecule that binds is the ligand. |
| GPCR | G protein-coupled receptor: a receptor threading through the membrane seven times, signalling by activating an intracellular G protein. Most peptide hormones act on one. |
| Agonist and antagonist | An agonist binds and activates; an antagonist binds and does not, blocking the site. A partial agonist gives a submaximal response however much is present, and so reduces the effect of a full agonist competing for the same site. |
| Affinity | How tightly a ligand binds, independent of what the binding does. Reported as the dissociation constant Kd, the concentration occupying half the receptors at equilibrium; lower means tighter. |
| Ki | The affinity of a competing compound, derived from a displacement experiment. Converting the measured IC50 into a Ki needs the Cheng-Prusoff correction, which is why an IC50 quoted without assay conditions is close to meaningless. |
| EC50 | The concentration producing half the maximum response in a functional assay. It measures potency, and it shifts with receptor expression level and cell line, so values are not portable between papers. |
| Efficacy | How large a response a ligand can produce at all, as distinct from how little of it is needed. High affinity with zero efficacy describes an antagonist. |
| Half-life | The time for half of a compound to be cleared from circulation. Unmodified peptides are frequently cleared within minutes, because proteases cut them and the kidney filters the pieces. |
| Bioavailability | The fraction of an administered amount reaching systemic circulation unchanged. Oral bioavailability for most peptides is very low, because digestion destroys them before absorption. |
| Parenteral | Administration by a route bypassing the digestive tract. The word appears here as vocabulary; no route is stated for any compound on this site. |
Research and regulation
| Term | Definition |
|---|---|
| In vitro, in vivo, ex vivo | In cells or isolated components; in a living organism; and in tissue removed from an organism but kept alive. The three answer different questions, and a result in the first is not evidence about the second. |
| Drug Identification Number | The DIN carried by a drug authorised for sale in Canada. It identifies a specific product from a specific manufacturer with specific authorised uses, not the molecule in general. |
| Research use only | A description of what material is supplied for. It is not a licence, not an exemption, and not an authorisation for human use, of which research chemicals have none. |
The regulatory terms are worked through in peptides and Canadian law, the pharmacology in how peptide receptor signalling is studied, and the design vocabulary — controls, blinding, power — in how to read a peptide study. For the chemistry underneath the whole vocabulary, start with peptides explained.
Material referred to on this site, including BPC-157 and bacteriostatic water, is supplied for laboratory research use only. Janoshik-verified by HPLC with mass-spec identity confirmation; 100% synthetic. The measured purity for each lot is stated on its product page.
Common questions
What is the difference between purity and peptide content? Purity is a proportion: how much of what is in the vial is the target compound. Content is a mass: how much target compound is actually there. Counter-ions and residual water push the two apart, and they come from different tests.
Is affinity the same as potency? No. Affinity is how tightly a molecule binds and is a property of the molecule-receptor pair. Potency is how much is needed to produce half a response, and depends on the assay as much as the molecule. They correlate and are not interchangeable.
Why does endotoxin matter if purity is high? Because a purity figure measures peptide against organic impurities on a chromatogram, and bacterial endotoxin does not show up there meaningfully. It is active at trace levels, so it can produce an inflammatory response that looks exactly like a result.
If a compound has a CAS number, is it approved? No. A CAS registry number is an identifier assigned so a substance can be referred to unambiguously. It carries no regulatory meaning whatsoever, and plenty of unapproved and investigational substances have one.
Selected Research References
- Cheng Y, Prusoff WH. Relationship Between the Inhibition Constant (Ki) and the Concentration of Inhibitor Which Causes 50 Per Cent Inhibition of an Enzymatic Reaction. Biochemical Pharmacology. 1973;22(23):3099-3108. pubmed.ncbi.nlm.nih.gov/4202581
- Muttenthaler M, King GF, Adams DJ, Alewood PF. Trends in Peptide Drug Discovery. Nature Reviews Drug Discovery. 2021;20(4):309-325. pubmed.ncbi.nlm.nih.gov/33536635
All products sold by NovaEvum are for research and laboratory use only. They are not intended for human or animal consumption, diagnosis, treatment, cure, or prevention of any disease.