![]() ![]() The concept of liposomes as drug-carriers to aid in selectivity was explored in the early nineteen seventies predominantly through the work of drug-transport scientists such as Gregoriadis who initially looked at the fate of protein-containing liposomes delivered into animals. Typically multiple unilamellar vesicles of differing sizes can form inside of each other generating multilamellar structures. Liposomes can vary in size from 25 nm to 2.5 µm and are classified within three broad categories : Multilamellar vesicles (MLV), which structurally resemble an onion with multiple concentric phospholipid bilayers separated by aqueous layers,large unilamellar vesicles (LUV) and small unilamellar vesicles (SUV) which have a single lipid bilayer surrounding the aqueous core. Natural liposomes have bilayers composed of phospholipids and/or cholesterol and as such are poorly antigenic, typically non-toxic and physiologically inert. Furthermore Papahadjopoulos and Watkins showed the differential permeability to anions and cations could be significantly altered with liposomes of different phospholipid compositions. However only when an ionophore, valinomycin, was utilised demonstrating selective diffusion of K+ over Na+ from liposomes containing equal concentrations of the ions, could liposomes be confirmed as entirely sealed membrane vesicles. The self-assembling ‘spherulites’, subsequently named liposomes from the greek lipo (fat) and soma (body), were recognised to be functionally analogous to studied biological membrane systems due to the similar rates of diffusion of ions. ![]() 275: 32444–32451.The discovery of liposomes initially came from studies by Bangham and Horne who observed by electron microscopy the self-association of the lipid phosphatidylcholine (mixed with or without cholesterol) in water formed ‘spherulites’ of varying sizes which had not a recognizable lamellar shell comprising a lipid bilayer. Pex5p in the Pex5p-Pexl4p membrane complex is a transmembrane protein. ![]() Gouveia A.M., Reguenga, C, Oliveira, M.E., Sá-Miranda, C, and Azevedo, J.E., 2000, Characterization of peroxisomal Pex5p from rat liver. Gouveia, A.M., Guimarães, C.P., Oliveira, M.E., Reguenga, C, Sá-Miranda, C, and Azevedo, J.E., 2003, Characterization of the peroxisomal cycling receptor, Pex5p, using a cell-free in vitro import system. 20: 7516–7526.įransen, M., Brees, C, Ghys, K., Amery, L., Mannaerts, G.P., Ladant, D., and Van Veldhoven, P.P., 2002, Analysis of mammalian peroxin interactions using a non-transcription-based bacterial two-hybrid assay. Collins, C.S., Kalish, J.E., Morrell, J.C., McCaffery, J.M., and Gould, S.J., 2000, The peroxisome biogenesis factors pex4p, pex22p, pexlp, and pe圆p act in the terminal steps of the peroxisomal matrix protein import. ![]()
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