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Giant Vesicles Exposed to Aqueous Two‐Phase Systems: Membrane Wetting, Budding Processes, and Spontaneous Tubulation
Author(s) -
Dimova Rumiana,
Lipowsky Reinhard
Publication year - 2017
Publication title -
advanced materials interfaces
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.671
H-Index - 65
ISSN - 2196-7350
DOI - 10.1002/admi.201600451
Subject(s) - vesicle , membrane , aqueous solution , polymer , nucleation , materials science , chemical engineering , membrane curvature , peg ratio , ethylene glycol , biophysics , liposome , phase (matter) , biological membrane , lipid bilayer , crystallography , chemistry , nanotechnology , organic chemistry , biochemistry , biology , finance , engineering , economics , composite material
In this review, we describe recent studies of giant unilamellar vesicles exposed to aqueous polymer solutions. These solutions undergo phase separation when the weight fractions of the polymers exceed a few percent. Depending on the lipid and polymer composition, the membrane may be completely or partially wetted by the aqueous phases. The deflation process induces a variety of vesicle shape transformations. One such transformation is droplet‐induced budding of the vesicles. Another, particularly striking transformation is the spontaneous tube formation, which reveals a substantial asymmetry and spontaneous curvature of the membranes, arising from the different polymer compositions across the membrane. The tubulation starts with the nucleation of small membrane buds which then grow into necklace‐like tubes. When the tube length reaches a certain critical value, the necklace‐like tube transforms into a cylindrical one. Analyzing different aspects of the observed vesicle shapes, quantitative estimates of the spontaneous curvature which is found to vary, depending on the lipid composition, between 1/(125 nm) and 1/(600 nm), are obtained. These curvatures are generated by the weak adsorption of poly(ethylene glycol) (PEG) molecules onto the lipid membranes, with a relatively small binding affinity of about 4 kJ mol −1 or 1.6 k B T per PEG molecule for either liquid‐ordered or liquid‐disordered membranes.