Peptide library is increasingly used to define antibody epitopes and substrate specificities of protein kinases. For epitope mapping, overlapping peptides are made to span the antigenic protein sequence. The antigenic determinant recognized by a monoclonal antibody can then be screened and defined. The alanine scanning method can also be used to assess that residue’s contribution to antibody binding and to determine which substitutions affect antibody recognition (mutational analysis). Unrelated synthetic peptides can be used to evaluate the antibody cross-reactivity.
Overlapping peptides from LifeTein were used to map the region of Fragment 3 by epitope mapping of anti-Fzd2 antibody. This anti-Fzd2 antibody was found to reduce tumor growth. Wnt signaling plays a critical role in colorectal cancer. Researchers found that Wnt receptor Frizzled2 (Fzd2) and its ligands Wnt5a/b are elevated in metastatic liver, lung, colon, and breast cancer cell lines. Their high level expression correlates with markers of epithelial-mesenchymal transition (EMT). By epitope mapping using synthetic peptides from LifeTein, the researchers mapped the epitope to a specific region. The antibody to Fzd2 was found to reduce cell migration and invasion. Targeting this pathway may provide a cure for patients with tumors expressing high amount of Fzd2 and Wnt5a/b.
We have developed an antibody to Fzd2 that reduces cell migration and invasion and inhibits tumor growth and metastasis in xenografts. We propose that targeting this pathway could provide benefit for patients with tumors expressing high levels of Fzd2 and Wnt5a/b.
Synthesis of multiple antigenic peptides: strategies and limitations
Dendrimeric platforms such as multiple antigenic peptides (MAP) can be synthesized either entirely by solid-phase methods (SPPS, direct approach) or by conjugation in SPPS-made building blocks (indirect approach).
SPPS is the preferred method by LifeTein. The synthesis approach requires a branched poly-lysine core. Each branch is elongated into the corresponding epitope by stepwise SPPS. The disadvantage of this approach is that the synthetic errors could happened and cause microheterogeneity in the final materials. However the cost is lower and less time-consuming than the indirect approach. For very long linear peptides, it is more advantageous to use the SPPS method.
The MAP synthesis may not always meet with success. The solubility of the peptide epitope can also become an issue and is difficult to predict for long epitopes. It is recommended to carefully design and analyze the linear epitope before MAP synthesis.
Studies showed that synthesis with Ahx linker in the lysine core had better isolated yield. It is possible that the flexibilizing effect of Ahx helps in keeping peptide chains properly solvated during synthesis, preventing aggregation and hence increasing the amount of viable growing peptide sequences.
LifeTein is pleased to offer a free, comprehensive web-based peptide analysis tool. This tool will allow your research team to overcome common difficulties inherent in protein analysis and peptide antigen design.
Cell-penetrating peptides (CPPs) such as the HIV TAT peptides are able to enter cell by direct translocation and endocytosis. Click here to see details about the CPP: http://lifetein.com/Cell_Penetrating_Peptides.html
Cell Penetrating Peptides
The following table shows a selection of currently known CPPs, their origins and sequences.
Currently, only two Food and Drug Administration (FDA) approved drugs for weight loss are available in the United States: the appetite suppressant phentermine and the inhibitor of fat absorption orlistat.
An MD Anderson group designed a new peptide drug: CKGGRAKDC-GG-D(KLAKLAK)2 (termed adipotide). This is a synthetic peptide that triggers cell death. These data showed that the peptide may be useful for treating obesity in humans.
Tthe MD Anderson group used a peptide library to screen and identify regions that bind to specific vascular cells. The interaction identified will be used as effective drugs to target particular protein functions.
This video explains factors that have contributed to the obesity epidemic.
Cell-penetrating peptides (CPPs) have the ability to enter a cell’s plasma membrane independent of a membrane receptor. Attached to a CPP, therapeutic cargo could be delivered to an intracellular target, thus overcoming the entry restrictions set by the plasma membrane.
Immune-based cancer treatments are one emerging type of therapy, and they show great potential. Synthetic-peptide-based vaccines, which are designed to elicit T cell immunity, are also a promising approach to the prevention and treatment of both infectious diseases and malignant disorders, such as cancer.