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Peptide synthesis services

N-ter / Internal / C-ter modification

 

Peptides can be modified at various positions including the free N-terminal amine group, side chains of some normal or modified amino acids or C-terminal carboxylic group.

The N-terminal extremity allows many modifications quite easily. The C-terminal extremity is generally more challenging to modify than the N-terminal extremity. The easiest alternative is to add an extra Lysine in C-terminal position, that can be labeled in side chain. Internal modifications consist generally in adding the conjugate of interest on the side chain of lysine, asparagine, serine, threonine or modified amino acids.

In any cases, the modification of a peptide can modify its properties and may for example decrease its bioactivity. This is hardly predictable and has to be tested.

List of classical peptide modifications

ModificationN-terC-terInternal
Acetylationx Lys side chain
Amidation x
Pyroglutamic acidx
Flurorescent dyexLys side chainLys side chain
Affinity tagxLys side chainLys side chain
Fatty acid(1)xLys side chainLys side chain
PhosphorylationThr, Ser, Tyr side chain
Spacer(2)xxx
Glycation(3)Ser, Thr, Asn side chain
Alcyne functionalizationxLys side chain, Pra side chain
Azide functionalizationLys side chain, Aha side chain

(1) Fatty acid

  • Stearic acid (C18)
  • Palmitic acid (C16). Improves the peptide penetration
  • Myristic acid (C14)
  • Capric acid (C10)

(2) Spacer

  • Ahx
  • PEG
  • O2Oc

(3) Sugar

  • Glucopyranosyl
  • Glucopyranoside
  • Galactopyranosyl
  • Mannopyranosyl
  • Fucopyranosyl
  • Xylopyranosyl