A
- Acetate salt
- The acetate salt form of a peptide, made by exchanging the trifluoroacetate counter-ion left by synthesis and purification.
- Adequate directions for use
- Directions under which a layman can use a drug safely and for its intended purposes; a drug without them is misbranded.
- Aggregation
- The association of peptide molecules into larger assemblies, from soluble oligomers to visible particles.
- Amino acid analysis
- Hydrolysing a peptide to its amino acids and quantifying each, to confirm composition and measure peptide content.
C
- C-terminal amide
- A peptide end in which the final carboxylic acid is replaced by a carboxamide (–CONH₂), removing its negative charge.
- C18 column
- An HPLC column packed with silica particles bonded to 18-carbon alkyl chains, the standard stationary phase for reversed-phase peptide analysis.
- CAS Registry Number
- A unique numeric identifier assigned to a chemical substance by the Chemical Abstracts Service.
- Certificate of analysis
- A document reporting the tests performed on one specific lot of a material, with their methods and results.
- Chromatographic purity
- The share of the total UV peak area in an HPLC chromatogram that belongs to the main peak, reported as a percentage.
- Counter-ion
- An ion of opposite charge that accompanies a charged peptide in the solid, such as trifluoroacetate, acetate or chloride.
- Cyclic peptide
- A peptide whose chain is closed into a ring, through its backbone ends, its side chains or a disulfide bond.
D
- D-amino acid
- The mirror-image form of an amino acid; natural proteins are built almost entirely from the L forms.
- Deamidation
- A degradation reaction in which an asparagine or glutamine side-chain amide is hydrolysed to an acid, adding about 1 Da.
- Disulfide bond
- A covalent S–S link between the side chains of two cysteine residues.
E
- Endotoxin
- Lipopolysaccharide from the outer membrane of Gram-negative bacteria, measured because it can confound cell-based in vitro assays.
H
- HPLC
- High-performance liquid chromatography: separates the components of a sample by how strongly each is held by a packed column, and measures each as it elutes.
- Hygroscopic
- Readily taking up water from the air; most lyophilised peptides are hygroscopic.
I
- Import alert
- An FDA notice that allows shipments of specified products or firms to be detained at the border without physical examination.
- In vitro
- Latin for "in glass": experiments carried out with cells, tissues or molecules outside a living organism.
- Intended use
- The purpose for which a seller intends a product, judged objectively from its statements, the product itself and the circumstances in which it is sold.
- Isoelectric point
- The pH at which a peptide carries no net charge; solubility is usually lowest near it.
K
- Karl Fischer titration
- A titration specific to water, used to measure the water content of a solid such as a lyophilised peptide.
L
- Lot traceability
- The ability to trace a unit of material back to its lot, and that lot to its testing, receipt and every place it went.
- Lyophilization
- Freeze-drying: removing water from a frozen solution by sublimation under vacuum, leaving a dry solid.
M
- Mass spectrometry
- An analytical technique that ionises molecules and measures their mass-to-charge ratio, used to confirm a peptide's identity from its molecular mass.
- Methionine oxidation
- Oxidation of methionine to methionine sulfoxide (+16 Da), the most common oxidative change in peptides.
- Molecular weight
- The mass of a molecule; for peptides, either the monoisotopic mass (most abundant isotopes only) or the average mass (natural isotope distribution).
N
- N-terminal acetylation
- Capping a peptide's free N-terminal amine with an acetyl group, which removes its positive charge.
- Net peptide content
- The fraction of a weighed peptide powder that is the peptide itself, the rest being counter-ions, bound water and residual solvent.
P
- Peptide bond
- The amide bond joining the carboxyl group of one amino acid to the amino group of the next.
R
- Research use only
- A labelling category for materials sold for laboratory research and not for human or veterinary use, diagnostics or any clinical purpose.
- Responsible corporate officer doctrine
- The rule that corporate officers in a position to prevent or correct a violation of the drug law can be criminally liable without proof that they took part in it.
- Retention time
- The time from the start of an HPLC run, when the sample is loaded onto the column, to the top of a component's peak.
S
- Solid-phase peptide synthesis
- The standard way peptides are made: amino acids added one at a time to a chain anchored on an insoluble resin.
T
- TFA salt
- The trifluoroacetate salt form of a peptide, the usual form after cleavage and reversed-phase purification with trifluoroacetic acid.
U
- Unapproved new drug
- A drug that is not generally recognised as safe and effective for its labeled uses and has no approved application, which may not be sold in interstate commerce.
W
- Warning letter
- FDA's written notice to a company that it considers the company to be in significant violation of the law, with a demand for correction.
For in vitro laboratory research only. Not for human or veterinary use. This library describes chemistry, analytical methods and published laboratory research; it gives no guidance on use in people or animals.