Peptide glossary

A common counter-ion in peptide salts. A peptide supplied as an acetate salt carries acetate ions associated with its basic residues, typically as a result of the final purification step.

Attachment of an acyl group, often a fatty acid chain, to a peptide. In research peptides it is commonly used to promote reversible binding to albumin.

A ligand that binds to a receptor and activates it. A dual or triple agonist activates two or three distinct receptors.

An organic molecule containing an amino group and a carboxyl group. Twenty standard amino acids are the building blocks of peptides and proteins.

A 37-amino-acid peptide hormone co-secreted with insulin by pancreatic beta cells. Amylin analogues are used in research on amylin and calcitonin receptor pharmacology.

A molecule whose structure is derived from a reference compound, with deliberate modifications such as substitutions, cyclisation or acylation.

A defined quantity of product made in a single production run under the same conditions. Its batch number links each unit to its manufacturing and analytical records.

A term used for a family of very short synthetic peptides (two to four residues) studied for their proposed effects on gene expression in specific tissues.

A phospholipid found almost exclusively in the inner mitochondrial membrane, important for the organisation of respiratory chain complexes.

A document reporting the results of analytical tests on a specific batch, such as identity by mass spectrometry and purity by HPLC. A COA applies only to the batch number it states.

A peptide that forms a coordination complex with a copper ion. GHK-Cu is the best-known example.

An ion that balances the charge of an ionised peptide in its solid form, for example acetate or trifluoroacetate.

A peptide in which part of the chain is joined to form a ring, by a disulfide bridge or a lactam bond for example. Cyclisation constrains the peptide's conformation.

The date up to which a batch is expected to remain within specification when stored as stated. It is printed on the label and recorded against the batch.

A peptide corresponding to a portion of a larger peptide or protein sequence, usually identified by its residue numbers.

The growth hormone secretagogue receptor. It is activated by ghrelin and by synthetic secretagogues such as ipamorelin.

Glucose-dependent insulinotropic polypeptide. One of the two principal incretin hormones, acting on the GIP receptor.

Glucagon-like peptide-1. An incretin hormone acting on the GLP-1 receptor, and a major target in metabolic research.

The G-protein-coupled receptor for glucagon. It is one of the three receptors targeted by retatrutide.

A hypothalamic peptide hormone that acts on the GHRH receptor. Synthetic GHRH analogues are used in research on the somatotropic axis.

An analytical technique that separates a sample into its components. Chromatographic purity is reported as the main peak's area as a percentage of total detected peak area.

Performed with cells or biological molecules outside their normal biological context, for example in culture or in a test tube.

Performed within a whole living organism, in contrast to in vitro.

A gut-derived hormone released after nutrient intake that amplifies insulin secretion. GIP and GLP-1 are the two principal incretins.

Freeze-drying. A solution is frozen and its ice removed by sublimation under vacuum, leaving a dry, more stable solid.

An analytical technique that measures the mass-to-charge ratio of ions. It is used to confirm a peptide's identity by comparing observed and theoretical molecular mass.

A family of five G-protein-coupled receptors activated by melanocortin peptides such as α-MSH.

A peptide encoded by a short open reading frame within the mitochondrial genome, such as MOTS-c or humanin.

Nicotinamide adenine dinucleotide. A coenzyme central to cellular redox reactions and a substrate for sirtuins and PARPs. It is not a peptide.

A short chain of amino acids linked by peptide bonds. By convention, peptides are chains of up to about 50 residues.

The amide bond formed between the carboxyl group of one amino acid and the amino group of the next.

The proportion of a lyophilised material's weight that is peptide, as opposed to water and counter-ions. It is distinct from chromatographic purity.

The share of detected material that is the target compound, usually by HPLC. It is a relative measure and does not by itself state quantity.

A protein that binds a specific signalling molecule (ligand) and initiates a cellular response.

A designation meaning a product is supplied for laboratory research. It is not for human or veterinary use, or for diagnostic or therapeutic purposes.

The ionic form in which a peptide is isolated, defined by its counter-ion. The salt form is part of a product's identity.

The order of amino acid residues in a peptide, written from the N-terminus to the C-terminus.

The standard method for making synthetic peptides. Amino acids are added one at a time to a chain anchored on an insoluble resin.

The temperature, light and humidity conditions under which a batch should be held to remain within specification. They are stated with batch documentation.