A
- Alpha helix (α-helix)
- A right-handed coiled backbone structure with about 3.6 residues per turn, stabilised by hydrogen bonds. Read more →
- Amino acid
- A molecule with an amino group, a carboxyl group and a side chain. Twenty standard amino acids are the building blocks of peptides and proteins. Read more →
- Amphipathic
- Having one water-loving face and one fat-loving face. A typical feature of antimicrobial peptides. Read more →
- Antimicrobial peptide (AMP)
- A short, usually positively charged peptide that kills or inhibits microbes, often by disrupting their membranes. Read more →
- Aspartimide
- A cyclic by-product that can form at aspartate residues during Fmoc synthesis, especially in Asp–Gly sequences. Read more →
- Average mass
- Molecular mass weighted across the natural abundance of each element's isotopes. Used when weighing out material. Read more →
B
- Beta sheet (β-sheet)
- Extended strands of peptide chain lying side by side and hydrogen-bonded to each other. Read more →
- Biased agonism
- When a molecule activates some signalling pathways of a receptor more than others. Read more →
C
- Certificate of analysis (COA)
- A document reporting test results, such as identity and purity, for a specific batch of material. Read more →
- Chirality
- The property of having a non-superimposable mirror image. Amino acids other than glycine exist in L and D forms. Read more →
- Chromatogram
- The detector trace from a chromatography run, with a peak for each separated component. Read more →
- Circular dichroism (CD)
- A spectroscopy method that estimates how much helix and sheet structure a peptide has in solution. Read more →
- Cleavage
- The final step of solid-phase synthesis, which releases the peptide from the resin and removes side-chain protecting groups. Read more →
- Counter-ion
- An ion, such as trifluoroacetate or acetate, that balances the charges on a peptide in its salt form. Read more →
- Cyclic peptide
- A peptide whose chain forms a ring, either head-to-tail or through side-chain links. Read more →
D
- D-amino acid
- The mirror-image form of an amino acid. Rare in nature but useful for making peptides resistant to enzymes. Read more →
- Deamidation
- Loss of the side-chain amide of asparagine or glutamine, changing the peptide's charge and adding about 1 Da. Read more →
- Deletion sequence
- An impurity missing one or more residues because a coupling step failed during synthesis. Read more →
- Disulfide bond
- A covalent sulfur–sulfur link between two cysteine residues. Read more →
E
- Electrospray ionisation (ESI)
- A mass spectrometry method that sprays a solution into charged droplets, often producing multiply charged ions. Read more →
- Endotoxin
- Lipopolysaccharide from the outer membrane of Gram-negative bacteria. A contaminant measured with the LAL test. Read more →
- Extinction coefficient
- How strongly a molecule absorbs light at a given wavelength. Used to measure concentration by UV. Read more →
F
- Fmoc
- Fluorenylmethyloxycarbonyl, a base-removable protecting group used in most modern solid-phase peptide synthesis. Read more →
G
- G protein-coupled receptor (GPCR)
- A receptor that crosses the cell membrane seven times and signals through G proteins. The main receptor family for peptide hormones. Read more →
- Good Manufacturing Practice (GMP)
- The quality standard medicines must be made under, enforced by regulators such as the MHRA. Read more →
H
- HPLC
- High-performance liquid chromatography, which separates components of a mixture so they can be measured. The standard method for peptide purity. Read more →
I
- Isoelectric point (pI)
- The pH at which a peptide has no overall charge. Read more →
L
- Lyophilisation
- Freeze-drying: removing water from frozen material under vacuum to give a stable dry powder. Read more →
M
- m/z
- Mass-to-charge ratio, the quantity a mass spectrometer actually measures. Read more →
- MALDI
- Matrix-assisted laser desorption/ionisation, a mass spectrometry method that mostly produces singly charged ions. Read more →
- Mass spectrometry (MS)
- A technique that measures the mass-to-charge ratio of ions. Used to confirm a peptide's identity. Read more →
- Monoisotopic mass
- The mass calculated using only the most abundant isotope of each element. Read more →
N
- N-terminus and C-terminus
- The two ends of a peptide chain: the free amino end (N) and the free carboxyl end (C). Sequences are written N to C. Read more →
- Native chemical ligation
- A method for joining two unprotected peptide fragments with a natural peptide bond, used to make long peptides and small proteins. Read more →
- Net peptide content
- The share of a powder's weight that is actually peptide, rather than counter-ions and water. Read more →
P
- Peptide
- A chain of amino acids joined by peptide bonds, usually from 2 to about 50 residues. Read more →
- Peptide bond
- The amide bond linking the carboxyl group of one amino acid to the amino group of the next. Read more →
- Peptidomimetic
- A molecule that mimics a peptide but has modified chemistry, for example to resist enzymes. Read more →
- Phage display
- A method that displays peptides on the surface of bacteriophages so huge libraries can be screened for binding. Read more →
- Placebo
- An inactive treatment given to a control group so its effects can be compared fairly. Read more →
- Protecting group
- A temporary chemical group that blocks a reactive site during synthesis. Read more →
- Purity (HPLC)
- The main peak's area as a percentage of the total peak area in a chromatogram. Read more →
R
- Randomised controlled trial (RCT)
- A study in which participants are randomly assigned to treatment or control groups. Read more →
- Residue
- An amino acid as it appears within a peptide chain, after losing water to form peptide bonds. Read more →
- Retention time
- How long a component takes to pass through a chromatography column to the detector. Read more →
- Reverse-phase chromatography
- Chromatography with a water-repelling column, where more hydrophobic molecules elute later. Read more →
S
- Scavenger
- An additive used during cleavage to trap reactive fragments before they damage the peptide. Read more →
- Solid-phase peptide synthesis (SPPS)
- Building a peptide one residue at a time while it's anchored to an insoluble resin bead. Read more →
- Stapled peptide
- A peptide held in a helical shape by a chemical brace linking two side chains. Read more →
- Surrogate endpoint
- A lab value or other marker used in place of a direct clinical outcome in a trial. Read more →
T
- Trifluoroacetic acid (TFA)
- A strong acid used in peptide cleavage and HPLC, often left behind as a counter-ion. Read more →
V
- Validation (analytical)
- Showing by experiment that a test method is fit for its purpose. Read more →