Peptide glossary

Plain definitions of the terms used on Solara's product pages and in Peptides 101: the material, the analysis and the paperwork.

Acetate

A counter-ion paired with the basic sites of a peptide, usually after an exchange step has replaced trifluoroacetate. Like any counter-ion, it is part of the mass of the powder. Read: Purity versus net peptide content

Amino acid

A molecule carrying an amino group and a carboxylic acid group. In the 20 standard amino acids both sit on the same (alpha) carbon; synthetic peptides can also carry non-standard ones. Read: What are peptides? A plain definition

Amino acid analysis

Measuring how much peptide a sample holds by breaking it down to its amino acids and quantifying each one. One route to net peptide content. Read: Purity versus net peptide content

Area-percent

The main peak's share of the total integrated peak area in a chromatogram. The usual way HPLC purity is reported. Read: What HPLC purity measures

Average molecular weight

A mass calculated with each element's natural mix of isotopes: the molecular weight given in reference databases such as PubChem. In mass spectrometry it is reported for larger peptides, whose lightest-isotope peak is too small to measure reliably. Read: Confirming identity by mass spectrometry

C-terminus

The end of a peptide chain whose carboxyl group is not part of a peptide bond, often a free acid or an amide. A sequence is written with the C-terminus last. Read: How a peptide sequence is written

Cake

The porous solid that freeze-drying leaves in a vial. Its shape follows the frozen solution it came from. Read: What lyophilized means

CAS number

A registry number the Chemical Abstracts Service assigns to one specific substance. A compound can carry more than one, for example for different salt forms.

Certificate of analysis

The document that ties one lot to the results of the tests run on it, each with its method, specification and result. Read: What a certificate of analysis shows

Collapse temperature

The temperature above which a frozen formulation softens during primary drying, so the cake shrinks and holds more water. Read: What lyophilized means

Counter-ion

An ion of opposite charge that balances a charged peptide in the solid, such as trifluoroacetate or acetate. Read: Purity versus net peptide content

Cyclic peptide

A peptide whose chain is closed into a ring by a bond between two of its parts. Read: Types of peptides: by length, shape and modification

D-amino acid

The mirror-image form of a chiral amino acid. Chains built by ribosomes use L-forms; a synthetic peptide can carry a D-residue by design. Read: D- and L-amino acids in synthetic peptides

Deamidation

The conversion of the side-chain amide of asparagine or glutamine to a carboxylic acid, with loss of ammonia, which adds about 0.98 Da to the mass. A common chemical degradation route. Read: Peptide degradation: deamidation, oxidation and cleavage

Drug Identification Number (DIN)

The eight-digit number Health Canada assigns to a drug product when it is authorized for sale in Canada. Solara's materials are supplied for research use only; they are not authorized drugs and carry no DIN. Read: Research grade versus pharmaceutical grade

Expiry

The date up to which a lot is expected to remain within its specification if stored under the stated conditions. Without a stated storage condition the date cannot be interpreted. Read: Reading a Solara label

Good manufacturing practices (GMP)

The system of manufacturing and quality controls required for drugs. In Canada it is set out in Part C, Division 2 of the Food and Drug Regulations. Solara's research materials are not GMP material. Read: Research grade versus pharmaceutical grade

HPLC

High-performance liquid chromatography: separating a sample's components on a packed column. Reverse-phase HPLC with UV detection near 214 nm is the usual peptide purity method. Read: What HPLC purity measures

International Nonproprietary Name (INN)

The generic name the World Health Organization assigns so that one substance carries one name worldwide. Read: How research peptides are named

Karl Fischer titration

A method that measures water directly, through a reaction that consumes iodine in proportion to the water present. Read: Karl Fischer titration: measuring water in a peptide powder

Lot

A defined quantity of material, made in one process or series of processes and identified by one lot number. Read: Reading a Solara label

Lyophilized

Freeze-dried: water removed from a frozen solution by sublimation under vacuum, leaving a dry, porous solid. Read: What lyophilized means

Mass spectrometry

Measuring molecular mass from the mass-to-charge ratio of ions. Used to check that a peptide has the mass its sequence predicts. Read: Confirming identity by mass spectrometry

Monoisotopic mass

A mass calculated with only the lightest isotope of each element. Reported for small peptides. Read: Confirming identity by mass spectrometry

N-terminus

The end of a peptide chain whose amino group is not part of a peptide bond, usually free but sometimes acetylated. A sequence is written with the N-terminus first. Read: How a peptide sequence is written

Net peptide content

The share of a weighed powder that is peptide, as opposed to counter-ions, water and salts. Read: Purity versus net peptide content

Peptide

A short chain of amino acids joined by peptide bonds, roughly two to fifty residues long. Read: What are peptides? A plain definition

Peptide bond

The amide bond that joins the carboxyl group of one amino acid to the amino group of the next, with the loss of one molecule of water. Read: The peptide bond: how amino acids join

Polypeptide

A longer chain of amino acids. Where a peptide becomes a polypeptide is a convention, not a fixed number. Read: Types of peptides: by length, shape and modification

Racemization

The unintended conversion of an amino acid from one mirror-image form toward the other, for example during synthesis. Read: D- and L-amino acids in synthetic peptides

Research use only (RUO)

A condition of supply: material sold for laboratory research and for nothing else. It is not a quality rating. Read: Research grade versus pharmaceutical grade

Residual moisture

The water left in a freeze-dried cake, expressed as a percentage of its mass. Read: Karl Fischer titration: measuring water in a peptide powder

Residue

An amino acid as it sits in a chain, after losing the water that forms each peptide bond. Read: The peptide bond: how amino acids join

Solid-phase peptide synthesis (SPPS)

Building a peptide one amino acid at a time on a chain anchored to resin beads, then cleaving it off and purifying it. Read: How synthetic peptides are made

Trifluoroacetate (TFA)

The counter-ion left from cleavage and purification with trifluoroacetic acid. It is part of the mass of many synthetic peptide powders. Read: Purity versus net peptide content