Amino-acid residue
The portion of an amino acid that remains as a unit within a peptide chain after bond formation. Peptide chains are described as sequences of amino-acid residues.
IUPAC Gold Book: amino-acid residue ↗Analyte
The component of a sample that an analytical procedure is intended to examine or measure.
IUPAC Gold Book: analyte ↗Batch or lot
A supplier or manufacturer identifier used to connect a defined group of material with its production, packaging, and analytical records. The identifier on a package should match the record being relied upon.
C Suite Biologics: how to read a peptide COA ↗C-terminus
The end of a peptide chain whose terminal residue has a carboxyl group that is not forming the next peptide bond. It is the opposite end from the N-terminus.
IUPAC Gold Book: amino-acid residue ↗Certificate of analysisCOA
A document reporting specified properties, methods, results, and identifiers for the material or sample named in the record. Its evidentiary scope is limited to the attributes tested and the sample or batch identified.
NIST: SRM definitions ↗Chromatogram
A presentation of detector response or another measure of effluent concentration against time or effluent volume. In an HPLC report, it is the graph behind the separated peaks.
IUPAC Gold Book: chromatogram ↗Chromatographic purity
A method-specific estimate of how much of the included detected signal is assigned to the principal chromatographic component. It is not automatically total peptide content, identity, sterility, or total mass purity.
C Suite Biologics: how to read a peptide COA ↗Detector response
The instrument signal produced as a detected component reaches the detector. Peak area or height reflects that response under the method conditions and is not necessarily a direct mass measurement without calibration.
IUPAC Gold Book: chromatogram ↗High-performance liquid chromatographyHPLC
A liquid-chromatographic technique that separates sample components through their different interactions with a mobile phase and a stationary phase. Reversed-phase HPLC is widely used in peptide analysis.
Hesse et al.: RP-HPLC strategies for peptidomics ↗Identity
The analytical question of whether the tested material or signal is consistent with the intended compound. Identity and chromatographic purity are related but separate claims.
C Suite Biologics: how to read a peptide COA ↗Liquid chromatography–mass spectrometryLC-MS
An analytical platform that couples liquid-chromatographic separation with mass-selective detection, allowing chromatographic peaks to be evaluated alongside mass-to-charge information.
John et al.: peptide quantification by LC-MS ↗Lot traceability
The documented connection among the ordered item, physical package, batch or lot identifier, and applicable analytical record. A report for a different lot does not establish the received unit's result.
C Suite Biologics: how to read a peptide COA ↗LyophilizationFreeze-drying
A drying process in which a frozen product is placed under vacuum so ice is removed primarily by sublimation, followed by removal of remaining unfrozen water. A lyophilized appearance does not by itself establish identity, purity, sterility, or quantity.
FDA: guide to lyophilization ↗Mass spectrometryMS
An analytical technique that forms and measures ions according to mass-to-charge behavior. In peptide analysis it can provide molecular-mass evidence that supports identity when interpreted with the method and acceptance criteria.
NCBI Bookshelf: HPLC-MS/MS Assay Guidance Manual ↗Mass-to-charge ratiom/z
The dimensionless quantity used in mass spectrometry to describe an ion's mass number divided by its charge number. A molecule may produce more than one observed charge state.
IUPAC Gold Book: mass-to-charge ratio ↗Measured quantity
The amount of analyte reported through an applicable quantitative procedure. A defensible quantity result states units, calibration or standards, calculation, and acceptance criteria.
John et al.: peptide quantification by LC-MS ↗Molecular mass
The mass of a molecule expressed in appropriate units. A mass-spectrometric result may support an expected molecular mass, but interpretation must account for charge states, adducts, isotopes, fragments, and instrument resolution.
NCBI Bookshelf: HPLC-MS/MS Assay Guidance Manual ↗N-terminus
The end of a peptide chain whose terminal residue has an amino group that is not acylated by the preceding amino-acid residue. Peptide sequences are conventionally written from N-terminus to C-terminus.
IUPAC Gold Book: amino-acid residue ↗Orthogonal method
A second analytical approach based on a different measurement principle. Orthogonal evidence helps prevent one method-specific result from being treated as proof of every material attribute.
C Suite Biologics: HPLC vs LC-MS ↗Peptide
A compound built from two or more amino-acid-derived units linked through covalent amide bonds. In ordinary biochemical usage, the chain is formed from amino-acid residues connected by peptide bonds.
IUPAC Gold Book: peptides ↗Peptide bond
The covalent amide linkage formed between the carbonyl carbon of one amino-acid-derived unit and the nitrogen of another, with formal loss of water during bond formation.
IUPAC Gold Book: peptides ↗Polypeptide
A peptide chain containing many amino-acid residues. The boundary among peptide, polypeptide, and protein is context-dependent rather than a universal fixed residue count.
IUPAC Gold Book: peptides ↗Reference materialRM
Material established as sufficiently homogeneous and stable for a specified measurement purpose, such as calibration, method assessment, assigning values, or quality control. Not every commercial research material is a certified reference material.
NIST: SRM definitions ↗Retention timetR
The elapsed time between sample injection and the peak maximum of the component of interest under the stated chromatographic conditions. It is method-dependent and should not be treated as a universal molecular identifier.
IUPAC Gold Book: total retention time ↗Sequence
The ordered arrangement of amino-acid residues in a peptide chain, conventionally written from the N-terminus toward the C-terminus. Sequence is a structural identity attribute, not a purity percentage.
IUPAC Gold Book: amino-acid residue ↗Specification
A stated requirement or acceptance range against which a result is compared. A result may conform to one specification while leaving other untested attributes unresolved.
C Suite Biologics: how to read a peptide COA ↗Ultraviolet detectionUV detection
Detection of components through their absorption of ultraviolet light at a stated wavelength. The response depends on molecular absorbance and method conditions, so peak area is not automatically equivalent to mass without suitable calibration.
Hesse et al.: RP-HPLC strategies for peptidomics ↗