MT2 and peptide testing glossary
Plain-language definitions of the terms used on Melanotan II certificates and throughout mt2.bio. Core terms have their own pages with Melanotan II examples; quick definitions follow below.
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Core terms
HPLC (high-performance liquid chromatography)
HPLC is a laboratory technique that separates the components of a sample by pumping it through a packed column; for peptides it is the standard method for measuring purity.
LC-MS (liquid chromatography–mass spectrometry)
LC-MS couples liquid chromatography with a mass spectrometer so that each separated component can be identified by its mass; it is the standard method for confirming a peptide's identity.
Peptide purity
Peptide purity is the share of the detected material in a sample that is the target peptide, usually reported as the main peak's percentage of total peak area in an HPLC chromatogram.
Net content
Net content is the laboratory's measured quantity of peptide in a tested vial, reported in milligrams.
COA (certificate of analysis)
A certificate of analysis is a laboratory's report of the tests performed on a specific sample, the methods used and the results.
Endotoxin testing (LAL assay)
Endotoxin testing detects lipopolysaccharide from the outer membrane of Gram-negative bacteria, most often with the Limulus amebocyte lysate (LAL) assay described in USP chapter <85>.
Lyophilized peptide
A lyophilized peptide is one that has been freeze-dried: frozen and then dried under vacuum so the ice sublimates, leaving a dry powder or cake.
Research use only (RUO)
Research use only is a designation for materials supplied solely for laboratory research by qualified personnel, not as drugs, foods, supplements or consumer products.
Lot number
A lot number is the unique identifier assigned to a batch of material that was produced, handled and tested as one unit; it links a vial to its certificate of analysis.
Analytical testing
Analytical testing is the laboratory measurement of a material's identity, purity, quantity and contaminants using defined, named methods.
Retention time
Retention time is how long a compound takes to travel through an HPLC column to the detector; it is characteristic of a compound only under one specific method.
Mass-to-charge ratio (m/z)
Mass-to-charge ratio (m/z) is the quantity a mass spectrometer measures: an ion's mass divided by its number of charges.
Quick definitions
- Accession number
- The laboratory's internal tracking number for a submitted sample.
- Acylation (lipidation)
- Attachment of a fatty-acid chain to a peptide, usually through a lysine side chain.
- Adduct
- An ion formed when a molecule picks up something besides protons, commonly sodium or potassium, written for example as [M+3H+K]4+.
- Agonist
- A molecule that binds a receptor and activates it.
- Aib (α-aminoisobutyric acid)
- A non-standard amino acid with two methyl groups on its α-carbon that constrains the peptide backbone.
- Amidation
- Replacement of the C-terminal carboxylic acid with an amide group.
- Area percent
- A peak's area as a percentage of total detected peak area; the usual way HPLC purity is reported.
- Charge state
- The number of charges on an ion, written as a superscript such as 3+ or 4+.
- Chromatogram
- The detector signal from an HPLC run plotted against time; each component appears as a peak.
- Counterion
- An ion such as acetate or trifluoroacetate that pairs with charged groups on a peptide as a salt. Counterions add weight to the powder but are not peptide.
- EC50
- The concentration that produces half the maximum response in an assay. Lower values indicate higher potency in that assay.
- Electrospray ionization (ESI)
- A soft ionization technique that turns molecules in solution into intact gas-phase ions, often with several charges.
- EU/mL
- Endotoxin units per milliliter, the unit for endotoxin levels and assay sensitivity.
- Lot
- A quantity of material produced and handled as one unit. Results on a certificate apply to one lot.
- m/z
- Mass-to-charge ratio, the quantity a mass spectrometer measures. A 1024 Da peptide carrying one extra proton appears near m/z 1025.
- PCR (polymerase chain reaction)
- A method that amplifies target DNA so it can be detected; used to screen for DNA from common microbial contaminants.
- Retention time
- The time at which a peak elutes. Characteristic of a compound under one specific method only.
- Reversed-phase HPLC
- HPLC that separates components mainly by hydrophobicity, using a hydrophobic column packing.
- Specificity
- A method's ability to measure the target compound without interference from other components; a validation characteristic in ICH Q2(R2).
Buy MT2
10 mg vials. Current lot KB32432 tested at 99.90% purity with identity confirmed by LC-MS. Current purchasing is available through Klow.bio.