PepGenex Science concepts

Each concept page explains one analytical or evidence term used across PepGenex Science, with cited references and a section on its limitations. The first sentence of each definition is shown below.

• Certificate of analysis (COA)

  A certificate of analysis (COA) is a document issued for one batch of a material that lists each test performed on that batch, the acceptance limits for each test and the numerical results obtained.

• HPLC purity

  HPLC purity is a purity result produced by high-performance liquid chromatography (HPLC), a separation technique that a methods review describes as extremely versatile for the isolation and purification of peptides.

• Identity testing

  Identity testing is analysis that confirms a material is the substance it is labeled as.

• Endotoxin testing

  Endotoxin testing is the measurement of bacterial endotoxin in a sample, most often with a Limulus amebocyte lysate (LAL) assay.

• Lyophilization (freeze-drying)

  Lyophilization, also called freeze-drying, is a process that removes water from a frozen material by sublimation and then desorption.

• Research use only (RUO)

  Research use only (RUO) is a labeling category meaning that a product is labeled as intended for research and not for other uses.

• Peptide

  A peptide is any compound produced by amide formation between a carboxyl group of one amino acid and an amino group of another.

• Receptor agonist

  A receptor agonist is a ligand that binds a receptor and activates it, so that binding is linked to a response in the cell.

• Mass spectrometry (MS)

  Mass spectrometry (MS) is an analytical technique that measures the mass-to-charge ratio (m/z) of ions.

• Peptide mapping

  Peptide mapping is an analytical method in which a protein or peptide is selectively fragmented into discrete peptides with enzymes or chemicals and the resulting fragments are analyzed, for example by HPLC.

• Chromatogram

  A chromatogram is the record of a chromatographic separation: a detector signal plotted against time as the separated components of a sample elute, with each detected component appearing as a peak at its retention time.

• Purity vs identity

  Purity and identity are separate quality attributes: an identity test establishes what a material is, while a purity test estimates how much of the material is the intended substance rather than other components.

• Endotoxin vs microbial testing

  Endotoxin testing is the measurement of bacterial endotoxin, the lipid A component of the lipopolysaccharide of Gram-negative bacteria, whereas microbial testing counts microorganisms or tests for their presence.

• Reference standard

  A reference standard is a characterized material against which a test sample is compared so that an analytical measurement can be interpreted.

• Lot traceability

  Lot traceability is the ability to connect a quantity of material, through its batch or lot number, to the records of how it was produced, tested and distributed.

• In vitro vs in vivo

  In vitro versus in vivo is the distinction between experiments performed on cells, tissues or purified molecules outside a living organism (in vitro) and experiments performed in a living organism (in vivo).

• Animal-to-human evidence

  Animal-to-human evidence is the question of whether, and how far, a finding observed in a living non-human animal holds in humans.

• Analytical method limitations

  An analytical method limitation is a boundary on what an analytical procedure can reliably report, set by what the procedure can distinguish, the smallest amounts it can detect or measure, the range over which it was validated and the conditions under which it is run.

• Net peptide content

  Net peptide content, also reported as peptide content or peptide mass fraction, is the proportion of the mass of a solid peptide material that is the peptide itself, as distinct from counterions, water, residual solvents and inorganic residue weighed along with it.

• Peptide content vs purity

  Peptide content and chromatographic purity are two different fractions of the same sample: chromatographic purity is the share of detected peak area that belongs to the main peptide, while peptide content is the share of the total sample mass that is peptide.

• Counterion content (acetate, TFA, chloride)

  Counterion content is the amount of oppositely charged ions, such as trifluoroacetate, acetate or chloride, that accompany a charged peptide in its solid salt form, usually reported as a mass fraction of the material.

• Lyophilized vs solution stability

  Lyophilized versus solution stability is the comparison between how a peptide or protein changes over time when it is kept as a freeze-dried solid and when it is kept dissolved in water.

• Storage conditions in stability guidance

  A storage condition is the defined combination of temperature, humidity and, where relevant, light exposure under which a material is held during a stability study, and to which its retest period or shelf life is tied.

• Sterility testing

  Sterility testing is a microbiological test that examines samples of a material for viable contaminating microorganisms.

• Heavy metals and elemental impurities testing

  Heavy metals testing is the measurement of metal and metalloid impurities in a material, a task current guidance frames as the control of elemental impurities.