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Modifications: N-Terminal and C-Terminal modifications

Peptides can be modified at the N terminus, in the middle or at the C terminus. In general, there are some standard peptide moieties accessible to be modified: N-terminal amino group, amino group of Lys, thiol group of Cys, hydroxyl groups of Ser, Thr, Tyr, guanidine group of Arg, and C-terminal carboxyl group.

Peptide synthesis: N and C terminal modifications

  • Acetylation/Amidation
  • N terminus
  • C terminus

Free Modifications: N-Terminal Acetylation and C-Terminal Amidation

Chemically synthesized peptides have free amino and carboxy termini. Please state any need for N-terminal acetylation or C-terminal amidation during the ordering process. It is impossible to perform these modifications after synthesis.

N-terminal acetylation and C-terminal amidation reduce the overall charge of a peptide so that the solubility may decrease. But the stability of the peptide could be increased because the terminal acetylation/amidation will generate a closer mimic of the native protein. Thus these modifications may increase the biological activity of a peptide.

Peptide synthesis: Amidation and Acetylation

Advantages:

  • The altered peptide ends are uncharged, so modified peptides more closely mimic the native protein. This increases their ability to enter cells. We recommend modification for intracellular, in-vivo assays and in-vitro functional studies.
  • The modifications increase the metabolic stability of the peptides and their ability to resist enzymatic degradation by aminopetidases, exopeptidases, and synthetase. The modified peptides can then be used as substrates in enzyme assays.
  • Amidation not only enhances the activity of peptide hormones, it also prolongs their shelf life.
  • The changes reduce the influence of charged C- or N-termini during ELISA binding assays.

Reference: The authors in this paper described the benefits of acetylation and amidation. They have been doing acetylation and amidation of their blocker peptides for years. In one of the publications (please see Biophysical Journal Volume 95 November 2008 4879–4889, figure 2). They described the advantages of using this procedures to improve the efficiency of blockers. Figure 2 in this publication provides experimental argumentation to illustrate that the acetylating the N-terminus and amidating the C-terminus improved the channel blocking efficiency of their peptides.

  • {Ac},Acetylation (Free)
  • {For}, Formylation
  • {Fmoc},9-Fluorenylmethyloxycarbonyl
  • {Suc},succinyl;{MeO-Suc}
  • {Cl-Ac},Chloroacetyl
  • {Mal}, Maleimide
  • {CBZ},Benzyloxycarbonyl
  • {Br-Ac},Bromoacetyl
  • Nitrilotriacetyl
  • {Boc},tertbutoxycarbonyl
  • {HPP},4-Hydroxyphenylpropionic acid
  • {LA}, Lipoic acid
  • {mPEG2000}, {mPEG3000}, {mPEG5000}, Mal-PEG12
  • {Alloc},allyloxycarbonyl
  • {Boc},tertbutoxycarbonyl
  • {But}, Butyric acid
  • {Hex}, Hexanoic acid
  • {Oct}, Octanoic acid
  • {Dec}, Decanoic acid
  • {Pal}, Palmitic acid
  • {Ste}, Stearic acid
  • {Myr}, Myristic acid
  • {Lau}, Lauric acid
  • More...

Peptide synthesis: N terminal modifications

  • {NH2}, Amidation (Free)
  • {CHO}, Peptide Aldehydes
  • {OL}, Alcohol Peptide
  • {CMK}, Chloromethylketone
  • {AMC},7-Amino-4-Methylcoumarin
  • {pNA},p-Nitroaniline
  • {-ONP}, para-nitrophenol
  • {-OSu}, hydroxysucinimide ester
  • ED, {AFC}, -OMe,-OtBu
  • {FMK}, Fluoromethylketone
  • {Cya}, Cysteamide
  • More...

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