Octalysine (K8) peptide

• Handling and Storage of Synthetic Peptides
• Material Safety Data Sheets (MSDS)

Batch to batch variation of the purity

The K8 peptide, an octalysine-modified cell-penetrating peptide, is a cationic peptide composed of eight lysine residues. It is structurally analogous to the octaarginine (R8) peptide but differs in its amino acid composition, replacing arginine with lysine. Studies comparing K8-modified liposomes (K8-Lip) with R8-modified liposomes (R8-Lip) have shown that K8-Lip exhibits similar physical properties, such as size and ζ-potential, but demonstrates significantly lower efficiency in promoting cross-presentation of antigen peptides. Unlike R8-Lip, K8-Lip does not enhance the C-terminal trimming of antigen-derived peptides, a critical step in generating mature MHC-I peptides. This functional disparity highlights the unique role of arginine-rich peptides in antigen processing.

Further investigations reveal that K8-Lip and R8-Lip share comparable cellular uptake mechanisms, primarily through macropinocytosis, and exhibit similar endosomal escape efficiencies in dendritic cells. However, K8-Lip fails to enhance proteasome-dependent C-terminal trimming of extended antigen peptides, such as SIINFEKLTEWTS, which is essential for efficient MHC-I presentation. These findings suggest that the lysine-rich structure of K8, unlike the arginine-rich R8, lacks the capacity to modulate proteasomal activity or downstream peptide processing, underscoring the specificity of arginine residues in optimizing antigen presentation pathways.

• Nakamura, T., Ono, K., Suzuki, Y., Moriguchi, R., Kogure, K., & Harashima, H. (2014). Octaarginine-modified liposomes enhance cross-presentation by promoting the C-terminal trimming of antigen peptide. Molecular pharmaceutics, 11(8), 2787–2795. https://doi.org/10.1021/mp500147y

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.