Signal Peptide (Targeting Sequence)
Definition
A short stretch at the start of a newly made protein that routes it to the right compartment and is then cleaved off. It is unrelated to a signaling peptide, which is a finished molecule that carries a message between cells; the two terms are a standing source of confusion.
Terms used in this definition
Other entries this definition refers to.
Where this term comes up
Entries whose definition mentions Signal Peptide (Targeting Sequence).
What this means for research sourcing
Structure and identity terms are what a certificate of analysis is written in. Every Volta compound ships with its sequence, molecular weight and measured purity, so these terms map directly onto the specification on the product page.
Related Terms in Chemistry & Structure
Dalton (Da)
The unit of molecular mass, one twelfth the mass of a carbon-12 atom. Peptides are quoted in daltons and proteins usually in kilodaltons, and the figure on a certificate is the monoisotopic or average mass depending on the method.
Isomer
A compound with the same molecular formula as another but a different arrangement of atoms. Isomers share a mass, so mass spectrometry alone cannot separate them and chromatography or a chiral method is required.
Molecular Formula
The count of each element in one molecule, written as a string such as C221H342N46O68. It fixes the molecular mass exactly, which is why a formula and a stated mass that disagree indicate an error in one of them.
Molecular Mass
The mass of one molecule, in daltons. The average mass uses the natural mixture of isotopes and the monoisotopic mass uses the lightest of each, and the two diverge by several daltons on a peptide of any size.
CAS Registry Number
A unique identifier assigned to a chemical substance by the Chemical Abstracts Service. It is specific to the exact substance, so a free base and its salt carry different numbers, and many research peptides have never been assigned one.
Fmoc (Fluorenylmethyloxycarbonyl)
The base-labile protecting group that dominates modern solid-phase peptide synthesis, removed with piperidine between couplings. It gives the strategy its name: Fmoc chemistry builds the chain under mild conditions no strong acid step is needed for.
Boc (tert-Butyloxycarbonyl)
An acid-labile protecting group, and the basis of the older synthesis strategy that preceded Fmoc. Boc chemistry requires repeated acid treatment and a harsh final cleavage, which is why it survives mainly for sequences Fmoc handles badly.
Protecting Group
A chemical group fitted to a reactive site so it stays out of the way while a reaction happens elsewhere, then removed. Peptide synthesis is largely the management of these: every amino acid side chain that could react has one.