Peptide Research Glossary

Entries below are general laboratory and directory vocabulary used on this site. They are not medical advice, dosing guidance, or product claims.

Peptide

A compound of amino acids linked in a chain by peptide bonds. Research peptides are typically short, chemically synthesized sequences used as laboratory materials.

Amino acid sequence

Also called: Primary structure

The order of amino acids in a peptide or protein, conventionally written from the N-terminus to the C-terminus using one-letter or three-letter codes.

Peptide bond

The amide linkage formed between the carboxyl group of one amino acid and the amino group of the next, which connects residues in a peptide chain.

Lyophilization

Also called: Lyophilized, Freeze-drying

A freeze-drying process that removes water from a frozen solution by sublimation under vacuum, leaving a dry cake or powder. A lyophilized peptide is stored dry until a diluent is added.

Reconstitution

Adding a sterile diluent to lyophilized material to produce a solution. Reconstitution is a laboratory preparation step, not a recommendation for use.

Bacteriostatic water

Also called: BAC water

Sterile water that contains 0.9% benzyl alcohol as a preservative. It is commonly used as a multi-draw diluent for reconstituting lyophilized peptides in laboratory settings.

Benzyl alcohol

An aromatic alcohol used at 0.9% in bacteriostatic water to inhibit bacterial growth in a multi-use diluent. It does not, by itself, determine whether a given peptide will dissolve.

Diluent

The sterile liquid added to lyophilized powder during reconstitution. Which diluent is suitable depends on the peptide's solubility and the laboratory protocol.

Concentration

The amount of dissolved peptide per unit volume of solution, often expressed as mg/mL or mcg/mL. Concentration is set by how much peptide and diluent are combined; it is not a recommended amount to use.

Certificate of analysis (COA)

Also called: COA

A batch document that reports analytical results for a specific lot, commonly including identity and purity tests. A COA describes the tested sample; it is not a certificate of safety or of fitness for a particular experiment.

See also: HPLC, Mass spectrometry, Lot number, Stores.

HPLC

Also called: High-performance liquid chromatography

An analytical method that separates mixture components as they pass through a column. Peptide COAs often report an HPLC purity value as the area-percent of the main peak.

Mass spectrometry

Also called: MS, LC-MS

An analytical technique that measures mass-to-charge ratios of ions. In peptide work it is used to check whether the observed molecular mass matches the mass expected from the sequence, often together with HPLC.

Purity percentage

The share of a chromatogram, typically HPLC area-percent, attributed to the main peak. Purity is not the same as identity, potency, sterility, or the absence of every impurity.

Lot number

Also called: Batch number

A producer-assigned identifier for a manufacturing batch. Vial labels and COAs should carry the same lot number so analytical results can be matched to the material.

U-100 insulin syringe units

Also called: Insulin syringe units

Graduations on a U-100 syringe where 100 units equal 1 mL, so 1 unit equals 0.01 mL. These units measure volume, not peptide mass.

Milligram

Also called: mg

A unit of mass equal to 0.001 gram. Lyophilized peptide vials are commonly labeled in milligrams of dry material.

Microgram

Also called: mcg, µg

A unit of mass equal to 0.000001 gram. One milligram equals 1,000 micrograms.

See also: Milligram, Peptide calculator.

Molecular weight

Also called: Molar mass, Dalton

The mass of one mole of a compound, expressed in g/mol or daltons (Da). Identity tests compare a measured mass to the molecular weight predicted from the amino acid sequence.

Half-life

The time in which the quantity of a substance in a given system falls by half, through elimination, degradation, or decay. A reported half-life applies to the conditions under which it was measured.

Aliquot

A measured subsample taken from a larger solution, often stored separately so the remaining stock is opened less often.

Research use only (RUO)

Also called: RUO

A label meaning the material is intended for laboratory research. RUO products are not licensed as medicines, diagnostics, or products for human or veterinary administration.

In vitro

Experimental work performed outside a living organism, such as in cell culture, isolated tissue, or a cell-free assay.

Vehicle

The medium in which a test article is dissolved or suspended for an experiment. For peptides this is often the reconstitution diluent or a further dilution buffer.

Definitions of common peptide-research terms: reconstitution, COA, HPLC, bacteriostatic water, purity, and related laboratory vocabulary. Research use only.