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Peptide Modification

Chinapeptide offers a wide range of peptide modification service including but not limited to the followings:

N-Terminus Modifications

C-Terminus Modifications

Other Modifications

Acetylation (Ac)

Amidation

Biotin and FITC Labeling

Formylation (For)

AMC

Disulfide Bridge

Fatty Acid

Aldehyde New!

Phosphorylation

Benzoyl (Bz)

Alcohol New!

BSA, KLH, OVA Conjugation

Benzyloxycarbonylation (CBZ)

Ester (OMe, OEt) New!

PEGylation

Bromoacetyl (Br-Ac)

p-Nitroaniline (pNA)

MAPS

Pyroglutamyl (pGlu) (Pyr)

NHMe, NHEt and Nhisopen

Cyclic Peptide

Succinylation (Suc)

tBu

Quenched Fluorescent Peptide

Tertbutoxycarbonyl (Boc)

TBzl

Special Amino Acid

3-Mercaptopropyl (Mpa)

Cysteamide (Cya)

Methyl and N-Methyl

 

1. Amidation and Acetylation

If the peptide is from an internal sequence of a protein, terminal amidation (C-terminus) or acetylation (N-terminus) will remove its charge and help it imitate its natural structure (amide, CONH2). In addition, this modification makes the resulting peptide more stable towards enzymatic degradation resulting from exopeptidases.

2. Biotin and FITC

For C-terminal labeling of biotin, a Lys residue is added to the C-terminus of the peptide. Biotin is then attached to the lysine side chain via amide bond. The positive charge of the lysine is then removed.

Fluorescein isothiocyanate (FITC) is an activated precursor used for fluorescein labeling. For efficient N-terminal labeling, a seven-atom aminohexanoyl spacer (NH2-CH2-CH2-CH2-CH2-CH2-COOH) is inserted between the fluorophore (fluoroscein) and the N-terminus of the peptide.

3. Disulfide Bridge

Peptide cyclization can be achieved through creating disulfide bridges between cysteine residues on the peptide. This is a challenging practice for peptide containing multiple cysteine residues due to random formations of disulfide bridges between them. Chinapeptide is able to build disulfide bridges between cysteine at specified positions. We are able to introduce up to three customized disulfide bridges on one peptide.

4. Phosphorylation

Phosphopeptides can assist in the investigation of the influences of phosphorylation on peptides and protein structure and in the understanding of regulatory processes mediated by protein kinases. Chinapeptide has successfully synthesized numerous serine-, threonine-, and tyrosine-phosphopeptides. For peptides containing one or more of these hydroxy-amino acids, selective phosphorylation can be achieved by orthogonal protection or by Fmoc-protected phosphorylated amino acids.

5. Methylation

The methylation of proteins has been established as an important modification that helps regulate cellular functions such as transcription, cell division, and cell differentiation. Post-translational N-methylation usually occurs on lysine or arginine sidechains. Peptides that represent methylated proteins are useful for protein-protein interaction studies or structural determination by x-ray crystallography.Chinapeptide can synthesize peptides containing mono-, di-, and tri-methylated lysines at >98% purity, as well as other methylation combinations.

6. BSA, KLH, OVA Conjugation

Peptide antigens are often too small to generate significant immune responses on their own. To solve this problem, these peptides are conjugated to bigger carrier proteins, such as bovine serum albumin (BSA), ovalbumin, or keyhole limpet hemocyanin (KLH). One of the advantages of KLH is that it does not interfere with ELISA or western blotting because it is not used as a blocking reagent. One common means of conjugation method is the maleimide method, which couples the cysteine residue of the peptide to the carrier protein. To perform this conjugation, one cysteine residue is added to the N- or C-terminus of the peptide so that it may be linked to the carrier protein.

Note: KLH is a large (MW = 4*105 to 1*107) aggregating protein. Because of its size and structure, its solubility in water is often limited, giving solutions and mixtures a cloudy appearance. This does not affect immunogenicity and the turbid solution can be used for immunizations.

6. PEGylation

PEGylation is the covalent conjugation of macromolecules (antibody, peptide, etc.) with polyethylene glycol (PEG), polymers that are nonionic, nontoxic, biocompatible and highly hydrophilic. The PEGylated macromolecules have enhanced therapeutic properties due to their increased solubility (for hydrophobic drugs) and bioavailability, masked antigenicity for minimum immune response in host, prolonged circulatory time within host through reduced renal clearance.

7. Isotope Labeling

For NMR measurement, we can label peptides with stable nonradioactive isotopes. Peptides labeled with 2H, 15N, 13C, or both 15N and13C can be synthesized for convenient detection in research. Please submit your sequence and request for a customized labeling of your peptides.

8. MAPS

Multiple antigen peptide application is one potent way to produce high-titer anti-peptide antibodies and synthetic peptide vaccines. This system utilizes the α- and ε-amino groups of lysine to form a backbone to which multiple peptide chains can be attached. Depending on the number of lysine tiers, different numbers of peptide branches can be synthesized. This eliminates the need to conjugate the antigen to a protein carrier.