- 214 nm detection
- The wavelength at which the peptide bond itself absorbs ultraviolet light, so every peptide is visible regardless of sequence. Certificates on this site report purity at 214 or 220 nm. Detection at 280 nm sees only tyrosine, tryptophan and cystine, and is used for quantitation rather than purity. Read more →
- Acetate salt
- A peptide whose counter-ion has been exchanged from trifluoroacetate to acetate. It changes the salt mass and can change solubility and tolerance in cell culture; it does not change the peptide itself. Read more →
- Acylation
- Attaching a fatty-acid chain to a peptide, usually through a lysine side chain and a short linker. The chain binds albumin, which is how PEP-SMG-1, PEP-TZP-2 and PEP-RTA-3 achieve their long half-lives. It also makes the molecule more hydrophobic and slower to dissolve. Read more →
- Adsorption
- Peptide sticking to the walls of a tube or plate, which removes it from solution at low concentration. Hydrophobic and basic peptides adsorb most. Low-binding plastics and carrier protein are the usual countermeasures. Read more →
- Aggregation
- Peptide molecules associating into clusters or fibrils instead of staying dissolved as single molecules. It shows as haze, loss of activity or a shift in HPLC, and it is favoured by high concentration, agitation and sequences rich in hydrophobic or beta-sheet-forming residues. Read more →
- Aliquot
- A measured portion of a stock solution set aside in its own tube so that each use thaws only what it needs. Aliquoting is the single most effective habit for extending the useful life of a reconstituted peptide. Read more →
- Amino acid analysis
- Hydrolysing a peptide completely to its free amino acids and quantifying each one. It confirms composition and is the reference method for how much peptide is actually present, which is the basis of net peptide content. It cannot report sequence, because hydrolysis destroys the order. Read more →
- Area percent
- How HPLC purity is calculated: the area under the main peak divided by the area under all peaks, times 100. It is a ratio of detector responses, not a weight, which is why a 99.5% area-percent figure and a net content in milligrams are two different measurements that both belong on a certificate. Read more →
- Bacteriostatic water
- Sterile water with 0.9% benzyl alcohol added as a preservative, used to reconstitute vials that will be drawn from more than once over the storage window. Read more →
- Benzyl alcohol
- The preservative in bacteriostatic water, at 0.9%, that keeps a multi-entry stock from growing organisms after the stopper has been pierced. It is also a solvent that some cell lines tolerate poorly, which is the reason to choose a diluent rather than default to one. Read more →
- Bioregulator
- The term the Khavinson group uses for very short synthetic peptides designed to reproduce the amino-acid composition of an organ extract: pinealon, vilon, epithalon and their relatives. The literature is largely from one laboratory, in cells and rodents, and that is how the term should be read. Read more →
- Blend
- Two peptides co-lyophilized in one vial at a fixed ratio. The certificate confirms each component's identity and reports its content separately; purity is a single figure for the mixture. Blends remove the variable of preparing two solutions but fix the ratio. Read more →
- C-terminal amidation
- Replacing the C-terminal carboxyl with an amide, subtracting one dalton and removing a negative charge. Many signalling peptides are amidated in nature, and a synthetic version that is not amidated is a different molecule with a different mass. Read more →
- CAS number
- The Chemical Abstracts Service registry number, a unique identifier assigned to a specific substance. It resolves the problem of one peptide having five names. Pepstral records a CAS only where one has been confirmed; fifteen catalogue compounds show none. Read more →
- Certificate of analysis (COA)
- The laboratory report for one lot of a product. A useful certificate names the laboratory, the method for each test, the lot number and the date, then reports purity, identity, net peptide content and endotoxin. Read more →
- Chromatogram
- The trace an HPLC detector draws: signal against time, with one peak per species that separated on the column. Reading one means finding the main peak, noting its retention time, and looking at what else appears before and after it. The certificate's purity line is the integration of that trace. Read more →
- Concentration-response
- An experiment run at several concentrations of a compound to see how the measured response changes with amount. It is the design that gives an EC50 and distinguishes a real effect from one seen at a single, arbitrary concentration. Read more →
- Conforms
- The word a certificate uses when a measured result meets the lot's specification. Every certificate line pairs a specification with a result; reading one means checking both, because 'conforms' against a loose specification says less than the number beside it. Read more →
- Counter-ion
- The charged partner left bound to a peptide after purification, typically acetate or trifluoroacetate. It adds weight to the powder without adding peptide, which is why gross weight and net peptide content differ. Read more →
- Cyclic peptide
- A peptide whose chain is closed into a ring, by a backbone bond, a disulfide, or a side-chain link. Cyclisation removes the free termini, which changes mass, stability and how the molecule fragments in tandem MS. Read more →
- D-amino acid
- The mirror-image form of an amino acid; the natural form is L. Swapping one residue to D changes nothing about the mass or the fragment ladder, so no mass-based method can confirm it. CJC-1295 carries a D-alanine and SS-31 a D-arginine; chiral amino acid analysis is the test that sees them. Read more →
- Deamidation
- The slow conversion of asparagine or glutamine side chains to their acid forms, adding one dalton and a negative charge. It is favoured by neutral-to-basic pH and by an asparagine followed by glycine, and it is one reason stocks are held cold and near neutral. Read more →
- Deletion sequence
- An impurity from synthesis in which one residue failed to couple, giving a peptide one residue short. It is close to the product in mass and retention and is the main thing a purity method has to resolve. Its presence at low level is normal; its level is what the certificate reports. Read more →
- Disulfide bond
- A covalent bridge between the sulfur atoms of two cysteine residues. It holds a loop closed, as in oxytocin, and its formation subtracts two daltons. A certificate mass that is two daltons low can mean the bridge is formed; two daltons high, reduced. Read more →
- Edman degradation
- A chemical sequencing method that removes and identifies one residue at a time from the N-terminus. It reads order directly and distinguishes leucine from isoleucine, but it needs a free N-terminal amine, so acetylated or pyroglutamate peptides give nothing in the first cycle. Read more →
- Endotoxin (LAL)
- Fragments of bacterial cell walls that survive sterilisation and provoke responses in cell-based and in-vivo work, measured by the limulus amebocyte lysate assay in endotoxin units per milligram. Certificates on file here report endotoxin against USP <85>; current lots read below 0.05 EU/mL. Read more →
- Expiry and retest date
- Two different dates: an expiry date is the end of a claimed shelf life; a retest date is when a lot should be re-examined before further use. Where a lyophilized peptide's date comes from, and what evidence sits behind it, is set out in the linked post. Read more →
- Extinction coefficient
- How strongly a molecule absorbs light at a given wavelength, per mole per centimetre. For peptides containing tyrosine, tryptophan or cystine it can be predicted from the sequence and used to measure concentration at 280 nm. Peptides without those residues cannot be quantified this way. Read more →
- Freeze-thaw cycle
- One round of freezing a solution and thawing it. Each cycle concentrates solutes as ice forms and can drive aggregation or degradation, which is why stocks are aliquoted rather than thawed whole. Read more →
- GPCR
- G-protein-coupled receptor, the largest family of cell-surface receptors and the target of most peptide hormones, including the incretin, melanocortin and growth-hormone-releasing peptides in this catalogue. Activation is usually read out as a second-messenger signal such as cAMP. Read more →
- Half-life
- The time for the amount of a compound to fall by half, in a given system. In the literature it refers to clearance from a living organism; on the bench the relevant figure is stability in solution, which is a different measurement. Read more →
- Heavy metals (ICP)
- Trace metals such as lead, mercury, arsenic and cadmium, measured by inductively coupled plasma spectrometry and reported in parts per million. The line appears on most certificates here as a 'below the reporting limit' result. Read more →
- HPLC purity
- The share of peptide-related material in a vial that is the target sequence, measured by high-performance liquid chromatography with UV detection at 214 nm and reported as a percentage of total peak area. It does not include water or counter-ions. Read more →
- Hygroscopic
- Readily absorbing water from the air. A lyophilized peptide cake is hygroscopic, which is why a vial is brought to room temperature before the stopper is disturbed: condensation onto a cold cake adds water and starts hydrolysis. Read more →
- Independent laboratory
- A testing laboratory the vendor does not own or control, which issues certificates in its own name and keeps its own record of them. The difference between an independent certificate and a vendor-generated one is whether a third party can be asked to confirm it. Read more →
- Issued date
- The date printed on a certificate when the laboratory released it, distinct from the date the sample was taken or the vial was filled. Across the certificates on file the report follows the sample by a median of six days. Read more →
- Laboratory water grades
- Sterile water, bacteriostatic water, water for cell culture and saline are different reagents with different additives and different uses. The right one depends on what the solution will be used for and how long it will be stored. Read more →
- LC-MS identity
- Confirmation that the main peak is the intended peptide, made by comparing the measured mass from mass spectrometry with the mass calculated from the amino-acid sequence. Read more →
- LC-MS/MS
- Liquid chromatography followed by tandem mass spectrometry. The main HPLC peak's ion is selected and broken along the peptide backbone, and the ladder of fragment masses is compared with the stated sequence. It is a sequence-level identity, used on the August 2026 lots, and stronger than a single mass. Read more →
- Lot number
- The identifier for one manufacturing and testing batch. The lot on the vial label must match the lot on the certificate in the COA library; if it does not, the certificate does not describe that vial. Read more →
- Lot report
- A monthly summary of every certificate the laboratory issued in that month: which compounds, which methods, what the results were, and what changed from the previous report. Reports are linked from the COA library. Read more →
- Lyophilized
- Freeze-dried. The peptide solution is frozen and the water removed under vacuum, leaving a dry porous cake that is stable for years when sealed and kept cold. Read more →
- MALDI-TOF
- Matrix-assisted laser desorption ionisation with time-of-flight detection: a mass-spectrometry method that reports the molecular ion without fragmenting it. Certificates issued before August 2026 on this site use it for identity. It confirms composition and mass; it does not read the order of residues. Read more →
- Mass spectrometry
- Measuring the mass of a molecule by ionising it and reading its mass-to-charge ratio. On a certificate it is the identity test: the observed mass is compared with the mass the formula predicts. A match rules out the wrong compound, deletion sequences, oxidation products and dimers in a single measurement. Read more →
- Methionine oxidation
- The most common degradation route for peptides containing methionine: the side-chain sulfur picks up an oxygen, adding 16 daltons and often shifting retention time. It is accelerated by light, air and metal ions, and is why some sequences are handled under tighter conditions than others. Read more →
- Micromole
- One millionth of a mole. A 5 mg vial of a 1,400-dalton peptide holds 3.6 micromoles; a 20 mg vial of a 418-dalton tripeptide holds 47.8. Comparing vials by micromoles rather than milligrams is how to compare what an experiment actually consumes. Read more →
- Molarity
- Concentration expressed as moles of solute per litre of solution. It is the unit experiments are designed in, because receptors respond to numbers of molecules, not to milligrams. Converting a label mass to molarity needs the molecular weight. Read more →
- Molecular formula
- The count of each element in one molecule, written C-H-N-O-S. It is derived from the sequence and determines the mass. Pepstral reads formulas from PubChem rather than from other suppliers' pages, and leaves the field blank where no record has been confirmed. Read more →
- Molecular weight
- The mass of one molecule in daltons, or of one mole in grams. It is the number that converts milligrams on a label into micromoles in an experiment, and the reason a 20 mg vial of a tripeptide holds far more molecules than a 5 mg vial of a 30-residue peptide. Read more →
- Monoisotopic and average mass
- Two ways to state a molecular mass. Monoisotopic mass counts only the most abundant isotope of each element; average mass weights every isotope by natural abundance. For a 4,000-dalton peptide they differ by about two daltons. A certificate's observed mass should be compared with the kind the method reports. Read more →
- N-acetylation
- Capping the N-terminal amine with an acetyl group, adding 42 daltons. It removes a positive charge and blocks aminopeptidase attack, and it makes Edman sequencing impossible without deblocking. Thymosin alpha-1 and N-acetyl semax carry it. Read more →
- N-terminus and C-terminus
- The two ends of a peptide: the N-terminus carries the free amine of the first residue, the C-terminus the free carboxyl of the last. Sequences are written N to C. Modifications at either end, such as acetylation or amidation, change the mass and often the behaviour. Read more →
- Net peptide content
- The fraction of a lyophilized powder's weight that is peptide, measured by amino-acid analysis. The remainder is counter-ions such as acetate or trifluoroacetate and bound water. Labelling by net peptide means the milligrams on the vial are peptide. Read more →
- Peptide bond
- The amide link between the carboxyl group of one amino acid and the amine of the next. Forming one releases a water molecule, which is why a peptide's mass is the sum of its residue masses plus one water, not the sum of its free amino acids. Read more →
- pH and buffer choice
- Hydrogen-ion concentration of a solution and the system that holds it steady. Peptide stability depends on it: aspartate isomerises and glutamine deamidates faster away from neutral, and solubility of a peptide changes with its net charge, which pH sets. Read more →
- Preclinical
- Research in cells, tissues or animals rather than in people. Most of what is published about the compounds in this catalogue is preclinical, and a result in a rodent model is a statement about the rodent model. Read more →
- PubChem CID
- The compound identifier in PubChem, the National Library of Medicine's open chemistry database. Formulas, masses and CAS numbers on this site are read from the PubChem record for each CID. Read more →
- Pyrogen
- Any substance that raises body temperature in a test animal. Bacterial endotoxin is the pyrogen most tests look for, but it is not the only one, so 'non-pyrogenic' and 'endotoxin below the limit' are related claims rather than the same claim. Read more →
- Pyroglutamate
- A cyclised N-terminal glutamine or glutamate that has lost water to form a ring, written pGlu or pE. It blocks the N-terminus like acetylation does. ARA-290 and thymulin begin with one. Read more →
- Racemisation
- Conversion of an L-residue to a mixture of L and D during synthesis, most often at histidine or cysteine. The product has the same mass and nearly the same retention, so it is invisible to a single-mass identity and only partly visible to HPLC. Read more →
- Receptor agonist
- A molecule that binds a receptor and activates it, as the natural ligand would. Many catalogue compounds are agonists at a named receptor, and the receptor is the most useful single fact about what a compound does in an assay. Read more →
- Reconstitution
- Adding water to a lyophilized vial to make a solution. Bacteriostatic water added slowly down the vial wall, then swirled, gives a known concentration: milligrams of peptide divided by millilitres of water. Read more →
- Research use only
- The sale condition for every product on this site: for in-vitro laboratory research by qualified personnel, not for human or animal use, diagnosis or treatment. Buyers confirm this at checkout. Read more →
- Residue
- One amino acid as it sits inside a peptide chain, having lost the water it gave up to form its bonds. Sequences are counted in residues; a 'tripeptide' has three. Read more →
- Retention time
- The minutes between injecting a sample onto an HPLC column and a species reaching the detector. Each peptide has a characteristic retention time under a given method, so a shift in retention is itself a finding. Very polar peptides, including the short bioregulators, elute early and close to the solvent front, which makes their purity harder to resolve. Read more →
- RP-HPLC
- Reversed-phase high-performance liquid chromatography: the method behind every purity figure on a Pepstral certificate. The sample is pushed through a column packed with hydrophobic particles; species that cling to the packing longer come off later, so the product and each impurity leave the column at their own time and are measured separately. Purity is the product's share of what the detector saw. Read more →
- Solid-phase peptide synthesis (SPPS)
- The method by which research peptides are made: amino acids are added one at a time to a chain anchored on resin beads, then the finished peptide is cleaved from the resin and purified by preparative HPLC. Read more →
- Solvent front
- The earliest point in a chromatogram, where material that did not interact with the column at all comes through. Peaks sitting on or near it are poorly resolved from one another, which is why an area-percent figure for a dipeptide or tripeptide carries less discriminating power than the same figure for a 30-residue peptide. Read more →
- Sterile filtration
- Passing a solution through a 0.22 µm filter to remove microorganisms. It does not remove endotoxin, and it can remove peptide by adsorption to the membrane, so the filter material matters for small volumes. Read more →
- Sterility test
- Culturing a sample to detect viable microorganisms. It answers a different question from the endotoxin test: a solution can be sterile and still carry endotoxin from organisms that died earlier. Some lots on this site carry a sterility line; it is listed when it was run. Read more →
- Stock solution
- A concentrated solution made once from the vial and then diluted into working concentrations. Making one stock and aliquoting it is how a laboratory avoids repeated freeze-thaw of the whole vial and keeps every experiment on the same starting material. Read more →
- Superseded certificate
- A certificate replaced by a newer one for the same product, usually because a new lot was tested. Pepstral keeps superseded certificates in the library, marked as such, so the history of a compound's lots can be read rather than only the current one. Read more →
- TFA salt
- A peptide supplied with trifluoroacetate as its counter-ion, left over from HPLC purification. The counter-ion adds mass to the vial that is not peptide, which is one reason net peptide content and gross weight differ. Acetate is the common alternative. Read more →
- Hundredth of a millilitre (0.01 mL)
- The smallest division most 1 mL laboratory syringes and air-displacement pipettes resolve cleanly, and the practical floor for a single draw. At 2.5 mg/mL it holds 25 mcg. Read more →
- Vehicle control
- The experimental arm that receives everything the treated arm receives except the peptide: the same water or buffer, the same preservative, the same volume. Without it an effect cannot be attributed to the peptide rather than to the solvent. Read more →
- Verification code
- The code printed on each Bioviridian certificate that can be entered on the laboratory's own search page to confirm the certificate exists in its records as published. It is what makes a certificate checkable rather than merely displayed. Read more →