CoPoP Liposomes

Cobalt porphyrin-phospholipid (CoPoP) liposomes are liposomes with cobalt-bound porphyrin- and palmitic acid-containing phosphatidylcholine (Cay-36128) embedded in the lipid bilayer. They can be used to capture His-tagged proteins and peptides via His tag binding to the cobalt of the porphyrin moiety in the lipid bilayer and can be used as immunization systems in animals. CoPoP liposomes have advantages over standard immunization systems in that they do not require a carrier protein to increase immunogenicity of short peptide antigens. In addition, peptide-CoPoP complexes are stable in biological media due to the His tag of the antigenic peptide being embedded within the hydrophobic lipid bilayer of the liposome. CoPoP liposomes with a captured His-tagged cyclic RGD peptide, which binds alphaVbeta3 integrin, and encapsulating sulforhodamine B (Cay-31539) selectively localize to subcutaneous tumors in a U87 mouse xenograft model. CoPoP liposomes with a captured His-tagged HIV gp41-derived membrane-proximal external region (MPER) peptide as an antigen and encapsulating the toll-like receptor 4 (TLR4) agonist monophosphoryl lipid A (MPL) induce anti-MPL IgG titers in mice and maintain titers at higher levels than similarly loaded nickel-nitrilotriacetic acid (Ni-NTA) liposomes with a captured MPER peptide.Synonyms: Cobalt Porphyrin-Phospholipid Liposomes. Formulation: (Request formulation change), 250 µg of CoPoP embedded into 2 mg of liposomes. Storage Buffer: TBS, pH 7.4, with 1% sucrose and 0.1% mannitol when resuspended in 1 ml of water. Applications: Carrier protein-free immunization of His-tagged proteins and peptides. CoPoP liposomes are suitable for loading 50 µg of His-tagged antigen per mg of liposomes.