Glossary

Peptide & verification glossary

Plain-language definitions for the peptide chemistry, analytical, and verification terms used across CertikLabs reports and documentation.

Verification Cryptography Manufacturing Purification Analytical Endotoxin testing Impurities Stability

Verification

COA (Certificate of Analysis): A signed document issued by a testing lab that lists the analytical results for a specific batch of peptide. Includes identity, purity, content, counter-ion, and storage conditions.
Batch / Lot: A single production run of a peptide. Every vial in the same batch shares the same starting materials and process; test results for one batch only apply to that batch.
Independent verification: Analytical testing performed by a laboratory that does not manufacture or sell the peptide, using standardized methods comparable across vendors.

Cryptography

SHA-256: A one-way cryptographic hash. CertikLabs hashes each finalized report and writes the hash to a public blockchain so the document is tamper-evident.
On-chain anchor: The public-blockchain transaction that records the SHA-256 hash of a verification report at the moment of issuance.

Manufacturing

SPPS (Solid-Phase Peptide Synthesis): The standard method for manufacturing peptides, in which the chain is built one amino acid at a time on a polymer resin from C-terminus to N-terminus.
Fmoc chemistry: The dominant SPPS protecting-group strategy. Uses 9-fluorenylmethyloxycarbonyl (Fmoc) as the temporary alpha-amine protecting group, removed with piperidine between coupling cycles.
Boc chemistry: An older SPPS strategy using tert-butyloxycarbonyl (Boc) as the alpha-amine protecting group, removed with TFA at each cycle. Still used for difficult sequences.
Resin: The insoluble polymer support to which the growing peptide is anchored during SPPS. Common types include Wang, Rink amide, and 2-chlorotrityl chloride.
Coupling reagent: A reagent (HBTU, HATU, DIC + Oxyma, PyBOP) that activates the carboxyl of an incoming amino acid for amide-bond formation with the resin-bound amine.
Global deprotection: The TFA-based cleavage step at the end of SPPS that simultaneously cleaves the peptide from the resin and removes all acid-labile side-chain protecting groups.

Purification

RP-HPLC (Reverse-Phase HPLC): Liquid chromatography on a non-polar stationary phase (typically C18). The standard separation method for peptide purity analysis and preparative purification.
Preparative HPLC: Large-scale HPLC used to physically separate and collect purified peptide fractions, as opposed to analytical HPLC used to measure purity.
Counter-ion exchange: Conversion of a peptide from one salt form (typically TFA) to another (typically acetate or HCl) by repeat HPLC in a different ion-pair acid or by ion-exchange resin.
Lyophilization: Freeze-drying. Removes water from frozen peptide solution under vacuum, producing a dry powder suitable for long-term storage.

Analytical

HPLC purity: The fraction of total integrated UV peak area attributable to the main peak. Method-dependent; usually measured at 214 nm for peptides.
LC-MS (Liquid Chromatography – Mass Spectrometry): An analytical method that combines HPLC separation with mass spectrometric detection. Used to confirm peptide identity by comparing observed mass to the theoretical mass of the declared sequence.
Monoisotopic mass: The mass of a molecule calculated using the most abundant isotope of each element. Reported by high-resolution mass spectrometers and used as the reference for peptide identity confirmation.
AAA (Amino Acid Analysis): Quantitative determination of peptide content by acid hydrolysis and quantification of the released free amino acids. Considered the gold-standard method for active peptide content.
Karl Fischer titration: The standard method for quantifying water content in a lyophilized peptide powder.
Ion chromatography: Chromatographic method used to quantify counter-ion content (TFA, acetate, chloride) of a peptide salt.

Endotoxin testing

Endotoxin: A heat-stable fragment of the outer membrane of gram-negative bacteria, specifically the lipopolysaccharide (LPS) molecule. The Lipid A portion triggers pyrogenic (fever) responses in humans via the TLR4/MD-2 receptor cascade.
LAL (Limulus Amebocyte Lysate): A bioassay that detects endotoxin by exploiting the blood-clotting cascade of horseshoe crab amebocytes. Three formats exist: gel-clot (qualitative), chromogenic (quantitative, colorimetric), and turbidimetric (quantitative, nephelometric).
Recombinant Factor C (rFC): An animal-free endotoxin assay that uses a single recombinant horseshoe-crab Factor C enzyme and a fluorogenic substrate. Recognized in Ph. Eur. 2.6.32 and accepted by the FDA as a compendial alternative to LAL under equivalence validation. Lower variability than LAL and fully synthetic.
Endotoxin Unit (EU): The standardized measure of endotoxin biological activity. One EU is defined operationally as the activity of approximately 0.1–0.2 ng of the international Reference Standard Endotoxin (RSE, E. coli O113:H10). Results are reported in EU/mL or EU/vial.
EU per vial (EU/vial): The total endotoxin load in a single reconstituted vial, calculated by multiplying the EU/mL assay result by the reconstitution volume. More actionable than EU/mL alone because dose depends on how much solution is drawn from the vial.
USP <85>: The United States Pharmacopeia general chapter that describes the bacterial endotoxins test, including gel-clot, kinetic chromogenic, and kinetic turbidimetric LAL methods, standard-curve requirements, and the 5 EU/kg/hour pyrogen threshold.
Ph. Eur. 2.6.14: The European Pharmacopoeia chapters that govern bacterial endotoxin testing: 2.6.14 covers LAL methods and 2.6.32 specifically addresses recombinant Factor C assays.
Lipid A: The phosphorylated glucosamine disaccharide anchor of lipopolysaccharide (LPS) that inserts into the bacterial outer membrane. It is the conserved molecular pattern recognized by the human TLR4/MD-2 innate immune receptor and is therefore the pyrogenic active site of endotoxin.
Pyrogen: Any substance that induces a febrile (fever) response when introduced into the body. Endotoxin is the most common pyrogen in peptide vials, but non-endotoxin pyrogens also exist. The pharmacopeial threshold is 5 EU per kg of body weight per hour (USP <85>).
Gel-clot LAL: The original compendial LAL format in which lysate and sample are incubated in a tube and then inverted after 60 minutes. A firm gel clot indicates endotoxin at or above the assay sensitivity (λ); no clot indicates absence. Qualitative or semi-quantitative only.
Chromogenic LAL: A quantitative LAL assay in which activation of the protease cascade cleaves a synthetic peptide substrate, releasing p-nitroaniline (yellow chromophore). The rate of absorbance increase at 405 nm is proportional to endotoxin concentration and is read against a standard curve.
Maximum Valid Dilution (MVD): The greatest dilution at which the sample can be tested while still detecting the endotoxin limit concentration. Calculated as MVD = C / λ, where C is the declared sensitivity of the lysate and λ is the assay sensitivity. Testing beyond the MVD invalidates the result.
Positive Product Control (PPC): A control sample prepared by spiking the test article with a known amount of standard endotoxin (typically 0.5 EU/mL). The spike must recover between 50% and 200% of nominal; failure indicates sample interference with the assay cascade and invalidates the run.
Spike recovery: The percentage of a known endotoxin spike recovered in the Positive Product Control. In-range recovery (50–200%) demonstrates that the sample matrix does not inhibit or enhance the LAL/rFC cascade; out-of-range recovery invalidates the result.

Impurities

Deletion sequence: An impurity peptide identical to the target except missing one amino acid, caused by a failed coupling cycle in SPPS.
Truncation: An impurity peptide consisting of only the first N residues of the target, caused by permanent capping of the growing chain during synthesis.
Racemization: Loss of stereochemistry at the alpha-carbon of an amino acid during SPPS, producing the D-isomer of an L-residue. Most common at Cys and His.
Deamidation: Spontaneous conversion of asparagine (Asn) to aspartate (Asp) or glutamine (Gln) to glutamate (Glu). One of the dominant solution-phase degradation pathways.
Aspartimide: A 5-membered succinimide intermediate formed at Asp-X sequences (especially Asp-Gly) during repeated piperidine treatment, hydrolyzing to a mixture of alpha- and beta-aspartate forms.
Methionine sulfoxide: The +16 Da oxidation product of methionine. The most common oxidative impurity in peptides exposed to air.
Disulfide scrambling: Rearrangement of disulfide bonds in a peptide during storage, producing the same sequence with a different disulfide topology and often substantially altered activity.
Residual TFA: Trifluoroacetate counter-ion remaining in a peptide isolated from TFA-containing HPLC mobile phase. Cytotoxic at high levels and removed by counter-ion exchange for most end uses.

Stability

Shelf life: The time period during which a peptide retains its labeled identity, purity, and content under specified storage conditions, supported by real-time stability data.
Freeze-thaw stability: The number of freeze-thaw cycles a reconstituted peptide solution can tolerate without measurable degradation. Best practice is to aliquot and freeze once.
ICH Q1A(R2): The international guideline that specifies how pharmaceutical stability studies are designed and conducted, including real-time and accelerated arms.

See also: Learn knowledge base · FAQ · Sample COA