to contain high concentrations of a conformationally intact membrane protein of interest. Integral Membrane proteins are involved in diverse biological functions and are targeted by nearly 50% of existing therapeutic drugs. However, because of their hydrophobic domains, membrane proteins are difficult to manipulate outside of living cells. Lipoparticles can incorporate a wide variety of structurally intact membrane proteins, including G protein-coupled receptors (GPCR)s, ion channels and viral Envelopes. Lipoparticles provide a platform for numerous applications including antibody screening, production of immunogens and ligand binding assays. Assembly The understanding of self-assembly of VLPs was once based on viral assembly. This is rational as long as the VLP assembly takes place inside the host cell (in vivo), though the self-assembly event was found in vitro from the very beginning of the study about viral assembly. Study also reveals that in vitro assembly of VLPs competes with aggregation and certain mechanisms exist inside the cell to prevent the formation of aggregates while assembly is ongoing. Linking targeting groups to VLP surfaces Attaching proteins, nucleic acids, or small molecules to the VLP surface, such as for targeting a specific cell type or for raising an immune response is useful. In some cases a protein of interest can be genetically fused to the viral coat protein. However, this approach sometimes leads to impaired VLP assembly and has limited utility if the targeting agent is not protein-based. An alternative is to assemble the VLP and then use chemical crosslinkers, reactive unnatural amino acids or SpyTag/SpyCatcher reaction in order to covalently attach the molecule of interest. This method is effective at directing the immune response against the attached molecule, thereby inducing high levels of neutralizing antibody and even being able to break tolerance to self-proteins displayed on VLPs. References External links Viral structural proteins