Last updated: June 2026
This glossary defines terms commonly encountered in research-peptide procurement, paperwork, and assay design. Definitions are written in a research-context register and do not constitute application or dosage guidance. Entries are listed alphabetically.
Amino Acid
An organic compound containing both an amine group and a carboxylic acid group, plus a side chain that distinguishes one amino acid from another. The 20 standard proteinogenic amino acids are the building blocks of peptides and proteins. Peptide sequences are conventionally written using either three-letter codes (Gly, Ala, Leu) or single-letter codes (G, A, L), reading from the N-terminus on the left to the C-terminus on the right.
Bacteriostatic Water for Injection (BWFI)
Sterile water containing 0.9% benzyl alcohol as a bacteriostatic preservative. The preservative inhibits microbial growth, which extends the shelf life of a reconstituted peptide solution under refrigerated storage. BWFI is a common solvent choice in research-context reconstitution where a solution used over multiple sessions is required.
Benzyl Alcohol
An aromatic alcohol used at 0.9% concentration as the bacteriostatic preservative in bacteriostatic water for injection. Benzyl alcohol inhibits microbial growth without significantly affecting the peptide chemistry of most short research peptides under refrigerated storage conditions. Benzyl alcohol is not compatible with all peptides or all assay formats; researchers should verify compatibility against the published peptide-chemistry literature.
C-terminus
The carboxylic-acid end of a peptide chain. By convention, peptide sequences are written with the N-terminus on the left and the C-terminus on the right. Some research peptides are presented with the C-terminus modified, for example as a primary amide rather than a free carboxylic acid, which is denoted by appending “-NH2” to the sequence.
Certificate of Analysis (COA)
The document the synthesis facility issues for each batch, recording the analytical results from that batch. A typical COA lists peptide identity, amino acid sequence, molecular formula, molecular weight, HPLC purity result, mass-spectrometry confirmation, appearance, and storage recommendation. A COA is the analytical evidence that ties a specific vial to a specific set of test results. Australian Peptide Hub publishes third-party Certificates of Analysis on its COA page.
Concentration
The amount of solute present per unit volume of solvent. Research-peptide concentrations are commonly expressed in milligrams per millilitre (mg/mL) or micrograms per millilitre (µg/mL). Conversion: 1 mg/mL equals 1,000 µg/mL.
Deletion Sequence
An impurity that arises during solid-phase peptide synthesis when one or more amino acid coupling steps fails. The result is a peptide chain shorter than the target sequence by one or more residues. Deletion sequences are the most common synthesis-related impurity in research peptides and appear as additional peaks on the HPLC trace. The ≥99% purity specification refers to the proportion of the target peptide relative to deletion sequences and other impurities.
Dimethyl Sulfoxide (DMSO)
A polar aprotic solvent used in peptide research when the target peptide is poorly soluble in aqueous buffers. DMSO is a strong solubiliser but also a strong cell-membrane penetrant, which can complicate assay design. Working dilutions in DMSO typically maintain final DMSO concentrations below 1% in the test buffer. DMSO is not a sterile solvent and is not a substitute for bacteriostatic water in research reconstitution.
Freeze-thaw Cycle
The process of freezing a reconstituted peptide solution and then thawing it for use. Repeated freeze-thaw cycles can degrade peptide stability through aggregation, oxidation, or precipitation.
High Performance Liquid Chromatography (HPLC)
An analytical separation technique in which a liquid sample is forced under high pressure through a column packed with a stationary phase. Components elute at different times based on their physicochemical interaction with the stationary phase and the mobile phase. HPLC is the standard purity assessment method for research peptides; the area under each peak on the resulting chromatogram is integrated to determine the proportion of the target peptide relative to impurities. Our catalogue is specified at HPLC ≥99% purity.
Hygroscopic
Tending to absorb moisture from the surrounding atmosphere. Lyophilised peptides are typically hygroscopic, which is why vials should be brought to room temperature before opening (to prevent condensation on cold glass) and then sealed immediately after use. Significant atmospheric moisture absorption can degrade lyophilised material over time.
Lyophilised
Freeze-dried under vacuum. Lyophilisation removes water from a frozen product by sublimation, producing a stable solid suitable for storage and shipment. Most research peptides ship lyophilised. To use a lyophilised peptide in a research assay, it must first be reconstituted in an appropriate solvent.
Mass Spectrometry (MS)
An analytical technique that measures the mass-to-charge ratio of ions. In peptide quality control, mass spectrometry confirms that the molecular weight of the synthesised material matches the theoretical molecular weight of the target sequence. A peptide COA typically lists both the theoretical molecular weight and the observed mass-spectrometry value, which should agree to within one mass unit for short research peptides.
Micrograms per Millilitre (µg/mL)
A common unit of concentration in research-peptide assays. 1,000 micrograms per millilitre equals 1 milligram per millilitre.
Milligrams per Millilitre (mg/mL)
A common unit of concentration, equal to one milligram of solute per millilitre of solution. Conversion: 1 mg/mL equals 1,000 micrograms per millilitre (µg/mL).
Molecular Weight
The mass of one molecule of a compound, expressed in daltons (Da) or grams per mole. For a peptide, the theoretical molecular weight is calculated from the sum of the residue masses minus water lost during peptide-bond formation. Molecular weight is listed on every COA and is the value confirmed by mass spectrometry during quality control.
N-terminus
The amine end of a peptide chain. By convention, peptide sequences are written with the N-terminus on the left and the C-terminus on the right. Some research peptides are presented with the N-terminus modified, for example acetylated (denoted “Ac-” at the start of the sequence), which can affect stability against amino-peptidase degradation.
Peptide
A short chain of amino acids linked by peptide bonds. The boundary between “peptide” and “protein” is conventional rather than strict; chains of up to roughly 50 amino acids are commonly described as peptides, with longer chains described as proteins. Research peptides are typically in the range of 2-45 amino acids.
Peptide Bond
The covalent amide bond formed between the carboxylic acid group of one amino acid and the amine group of the next, with loss of one water molecule. Peptide bonds are the linkages that define the primary structure of a peptide or protein. The directionality of these bonds is the reason peptide sequences are read N-to-C.
pH
A logarithmic measure of hydrogen-ion activity in an aqueous solution. Peptide solubility and stability are typically pH-dependent. The pH of a reconstituted peptide solution depends on the choice of solvent and the peptide’s own acid-base properties. Some research peptides require buffered solvents rather than plain water or bacteriostatic water to maintain stability across the shelf life.
Purity
The proportion of the target compound relative to total material in a sample. For research peptides, purity is conventionally reported as an HPLC area percentage. A ≥99% HPLC purity specification means the target peptide accounts for at least 99% of the total integrated peak area on the HPLC trace.
Research Peptide
A short chain of amino acids supplied in lyophilised form for in-vitro laboratory and scientific investigation. Research peptides are not pharmaceutical products, are not formulated for human use, and are not assessed for therapeutic safety or efficacy. They are research-grade reagents.
Residue
An individual amino acid unit within a peptide or protein sequence. A peptide composed of 10 amino acids is described as a 10-residue peptide or a decapeptide. The molecular weight of a peptide is calculated from the sum of residue masses minus water lost during the formation of each peptide bond.
Sequence
The ordered list of amino acid residues that defines a peptide’s primary structure. Sequences are conventionally written N-to-C using either three-letter codes (Gly-Ala-Leu) or single-letter codes (GAL). The sequence is the fundamental identity descriptor of any research peptide and appears on every COA.
Solid-phase Peptide Synthesis (SPPS)
The standard method for chemical synthesis of research peptides. An amino acid is anchored to an insoluble resin support, and additional amino acids are added one residue at a time through repeated cycles of coupling and deprotection. After the full sequence is assembled, the peptide is cleaved from the resin and purified by reverse-phase HPLC. SPPS is the synthesis method behind essentially all commercially supplied research peptides.
Solubility
The capacity of a peptide to dissolve in a given solvent at a given temperature and concentration. Peptide solubility is sequence-dependent: hydrophobic sequences may require organic co-solvents, while highly charged sequences typically dissolve readily in aqueous buffers. Solubility is the primary consideration in choosing a reconstitution solvent.
Stability
The property of remaining chemically intact over time under specified storage conditions. Peptide stability depends on sequence (for example, methionine residues are prone to oxidation), storage temperature, storage state (lyophilised versus reconstituted), and solvent choice. Lyophilised peptides are typically stable for years under -20°C storage; reconstituted peptides have shorter shelf life.
Storage Temperature
The temperature at which a research peptide is held during storage. Industry-standard recommendations for lyophilised research peptides are 2-8°C for short-term storage and -20°C or lower for long-term storage. Reconstituted peptide stocks are typically held at 2-8°C within the shelf life indicated by the peptide chemistry literature or the COA.
Sublimation
The phase transition from solid directly to gas without passing through the liquid state. Sublimation is the physical mechanism by which lyophilisation removes water from a frozen product under vacuum. Understanding sublimation explains why lyophilised peptides arrive as a dry pellet or powder rather than as a dried-down film.
Vial
The glass container holding a lyophilised research peptide. Research peptide vials are typically tubular borosilicate glass with a rubber stopper and a crimped aluminium seal. Some peptides ship in amber glass vials, which provide additional protection against light-sensitive degradation. The vial itself is not sterile for human-use purposes; it is a research-context container.
Regulatory & Use Disclaimer
The products listed on this site are supplied exclusively for in-vitro laboratory and scientific investigation purposes. They are not for human or veterinary use, therapeutic application, or diagnostic purposes. No therapeutic, dosage, or outcome statements are made or implied. Australian researchers are responsible for ensuring compliance with all applicable laws and regulations regarding research peptides.