Capping
Definition
Permanently blocking any chain that failed to couple, so it cannot react in later cycles. It converts a deletion impurity that would be hard to separate into a short truncated one that is easier to remove.
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
Coupling Reagent
The activator that turns a carboxylic acid into a form reactive enough to form an amide bond with the next amino group. Coupling efficiency compounds over a synthesis, so a small per-step loss becomes a large one over a long sequence.
Carbodiimide
A class of coupling reagent including DIC and EDC, usually paired with an additive to suppress side reactions. They are inexpensive and widely used, and the by-product they form differs in how easily it washes away.
HOBt (Hydroxybenzotriazole)
A coupling additive that forms a more selective active ester, raising yield and suppressing racemisation. Its shipping restrictions as a dry solid are part of why alternatives such as Oxyma came into use.
Uronium Salt
A family of fast coupling reagents including HBTU and HATU. They activate quickly and are used where a difficult coupling needs the help, at a higher cost than a carbodiimide.
Oxyma Pure
An additive used in place of HOBt, giving comparable suppression of racemisation without the same handling classification. It is typically paired with a carbodiimide.
Piperidine
The base used to remove the Fmoc group, usually as a 20% solution in DMF. It appears once per residue in a standard synthesis, and the by-product it forms is monitored to confirm each deprotection happened.
Resin
The insoluble polymer bead the chain is assembled on in solid-phase synthesis. Anchoring the chain to it is what lets excess reagents and by-products be washed away at every step, which is the entire advantage of the method.
Wang Resin
A resin whose linker releases the chain as a free carboxylic acid at the C-terminus. The choice of resin decides the C-terminal form, which is why it is picked before the first residue is attached.