FcIII peptide

• COA/MS/HPLC Report
• Handling and Storage of Synthetic Peptides
• Material Safety Data Sheets (MSDS)

Batch to batch variation of the purity

The FcIII peptide is a 13 amino acid peptide (DCAWHLGELVWCT) that has been shown to bind competitively to hinge region on the Fc fragment of IgG with high affinity. It was initially identified through a bacteriophage display screen. A modified version of the FcIII peptide, called Bio-Ox, was developed to increase solubility and enable competitive elution of protein complexes in their native state. Further modifications were made to improve solubility, resulting in a new reagent called PEGylOx. PEGylOx is an FcIII peptide that is N-terminally PEGylated with a four-unit polymer and cyclized by oxidation of the cysteines to cystine. PEGylOx has been used for the rapid, native elution of protein complexes containing a Protein-A-tagged component from yeast and bacteria.

There is another modified peptide,Fc-III-4C (Cat.# 319362), H-CDCAWHLGELVWCTC-OH, (C1-C15, C3-C13 disulfide bridges). The binding affinity of Fc–III–4C tag to human IgG is measured as 2.28 nM (Kd) and is 100 times higher than that of the Fc-III tag to IgG.

The primary sequence of Fc-III peptide was DCAWHLGELVWCT, in which Cys 2 and Cys 12 form a disulfide linkage that make the peptide has a cyclic structure.

• LaCava J, Chandramouli N, Jiang H, Rout MP. Improved native isolation of endogenous Protein A-tagged protein complexes. Biotechniques. 2013 Apr;54(4):213-6. doi: 10.2144/000114012. PMID: 23581468; PMCID: PMC3667664.
• Gong Y, Yi M, Zhang L, Feng S, Deng H. Characterization of the Fc-III-4C-based recombinant protein expression system by using carbonic anhydrase as the model protein. Protein Expr Purif. 2021 Jan;177:105761. doi: 10.1016/j.pep.2020.105761. Epub 2020 Sep 19. PMID: 32956801.

Trifluoroacetic acid (TFA) is a common counterion from the purification process using High-Performance Liquid Chromatography (HPLC). The presence of TFA can affect the peptide's net weight, appearance, and solubility.

Impact on Net Weight: The TFA salt contributes to the total mass of the product. In most cases, the peptide content constitutes >80% of the total weight, with TFA accounting for the remainder.

Solubility: TFA salts generally enhance the solubility of peptides in aqueous solutions.

In Biological Assays: For most standard in vitro assays, the residual TFA levels do not cause interference. However, for highly sensitive cellular or biochemical studies, please be aware of its presence.