Definitions of the analytical, pharmacological and handling terms used across research peptide documentation. For a practical walkthrough of batch analysis, see our guide to reading a certificate of analysis.
Aib
Aminoisobutyric acid, a non-proteinogenic residue often substituted into incretin analogs to block cleavage by DPP-4.
Amidation
Conversion of the C-terminal carboxylic acid to an amide (-NH2), mimicking many native hormones and improving stability. Written as a -NH2 suffix.
AMPK
AMP-activated protein kinase, a cellular energy sensor and a common readout in mitochondrial peptide research.
Certificate of Analysis (COA)
A batch-specific analytical report recording the testing performed on one production lot, including identity, purity and often net peptide content.
Class B1 GPCR
The G-protein-coupled receptor family that includes the GLP-1, GIP and glucagon receptors. A large extracellular domain captures the peptide C-terminus while the N-terminus inserts into the transmembrane bundle.
DAC
Drug Affinity Complex, a maleimide group that forms a covalent bond with cysteine-34 of serum albumin to extend circulating half-life.
Deamidation
Loss of an amide group from asparagine or glutamine, a common degradation pathway that adds roughly 1 Da to observed mass.
DPP-4
Dipeptidyl peptidase-4, the enzyme that cleaves native GLP-1 and GIP at the position-2 residue, giving them half-lives of minutes.
ESI-MS
Electrospray ionisation mass spectrometry. Produces multiply charged ions and pairs naturally with liquid chromatography for LC-MS.
Freeze-thaw cycle
One transition from frozen to thawed and back. Each cycle imposes stress and allows condensation, which is why aliquoting on first opening is standard.
GHRH analog
A synthetic analog of growth hormone-releasing hormone, acting at the GHRH receptor on the anterior pituitary. Sermorelin and tesamorelin are examples.
Hygroscopic
Readily absorbing atmospheric moisture. Lyophilised peptides are hygroscopic, which is why vials should reach room temperature before opening.
Incretin
A gut-derived hormone that potentiates glucose-dependent insulin secretion. GLP-1 and GIP are the two principal incretins.
Karl Fischer titration
The standard method for measuring water content in a lyophilised solid.
Lyophilisation
Freeze-drying. Removes water under vacuum, leaving a stable dry cake and greatly slowing hydrolysis and deamidation.
MALDI-TOF
Matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry. Tends to produce singly charged ions and tolerates salts well.
Net peptide content
The proportion of vial weight that is actually peptide, excluding counter-ion and residual water. Typically 70-90%, determined by amino acid or nitrogen analysis.
RP-HPLC
Reversed-phase high-performance liquid chromatography, the standard purity method for peptides. Purity is main peak area over total peak area.
Secretagogue
A compound that stimulates secretion of a hormone. Ipamorelin is a selective growth hormone secretagogue.
TFA salt
Trifluoroacetate, the counter-ion left by reversed-phase purification. Contributes mass and is cytotoxic above certain concentrations in cell culture, so acetate salts are used where that matters.
Thymosin beta-4
A 43-residue actin-sequestering peptide. Published work often concerns the full-length protein or its LKKTETQ actin-binding motif.
Triple agonist
A single engineered peptide activating three receptors, characterised by relative potency at each rather than maximal activity at all.
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