Real-Time Observation of Polyelectrolyte-Induced Binding of Charged Bilayers

Luan, Yuxia; Ramos, Laurence

doi:10.1021/ja073412h

Cited by 14 publications

(10 citation statements)

References 71 publications

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“…The binding of multiple bilayers shown here, mediated by MPS-PPV, presumably arises from MPS-PPV chains that lie intercalated between lipid bilayers. Similar behavior has been reported for other polyelectrolyte-lipid interactions (27).…”

Section: Resultssupporting

confidence: 87%

Unraveling electronic energy transfer in single conjugated polyelectrolytes encapsulated in lipid vesicles

Karam

Ngo²,

Rouiller³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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A method for the study of conjugated polyelectrolyte (CPE) photophysics in solution at the single-molecule level is described. Extended observation times of single polymer molecules are enabled by the encapsulation of the CPEs within 200-nm lipid vesicles, which are in turn immobilized on a surface. When combined with a molecular-level visualization of vesicles and CPE via cryo-transmission electron microscopy, these single-molecule spectroscopy studies on CPEs enable us to directly correlate the polymer conformation with its spectroscopic features. These studies are conducted with poly[5-methoxy-2-(3-sulfopropoxy)-1,4-phenylene-vinylene] (MPS-PPV, a negatively charged CPE), when encapsulated in neutral and in negatively charged lipid vesicles. MPS-PPV exists as a freely diffusing polymer when confined in negatively charged vesicles. Individual MPS-PPV molecules adopt a collapsed-chain conformation leading to efficient energy migration over multiple chromophores. Both the presence of stepwise photobleaching in fluorescence intensity-time trajectories and emission from low-energy chromophores along the chain are observed. These results correlate with the amplified sensing potential reported for MPS-PPV in aqueous solution. When confined within neutral vesicles, single MPS-PPV molecules adopt an extended conformation upon insertion in the lipid bilayer. In this case emission arises from multiple chromophores within the isolated polymer chains, leading to an exponential decay of the intensity over time and a broad blueshifted emission spectrum.lipid-polymer interaction | exciton migration | water-soluble light-emitting polymer | biosensing C urrent knowledge on how the interplay of polymer conformation and chromophore coupling affect energy transfer along a conjugated polymer backbone has been established following rigorous ensemble and single-molecule spectroscopy studies. Many of these studies involve polyphenylene vinylene (PPV)-based conjugated polymers decorated with alkyl side groups that facilitate their solubility in organic solvents. This knowledge is critical for developing conjugated polymer-based electroluminescent, photovoltaic, and sensor devices (1).The prevailing organization of a polymer backbone is expected to have direct effects on the coupling of neighboring chromophores (planar segments with delocalized π orbitals along the backbone) and on the energy transfer efficiency between these chromophores. Collapsed polymers, predominantly encountered in films prepared from poor solvents, exhibit long-range order where chains are found in close proximity, folded back on themselves (2, 3). Polymers will thus undergo efficient interchain or through-space energy transfer. On the contrary, polymers in solution are highly disordered, where the presence of defects along the chains together with freely accessible bond rotations should result in globular structures with larger intramolecular distances, on average. The predominant mode of energy transfer found in this case is through-bond or intramolecular ener...

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Section: Resultssupporting

confidence: 87%

Unraveling electronic energy transfer in single conjugated polyelectrolytes encapsulated in lipid vesicles

Karam

Ngo²,

Rouiller³

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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“…The existence of such a trans-bilayer movement does not seem unlikely, because the lipid film is probably under considerable stress due to its strong and asymmetric interaction with the support. 44 This situation would be consistent with the existence of membrane defects. 45 It also must be taken into account that the headgroup of the label contains the bulky and less water soluble fluorophore.…”

supporting

confidence: 74%

Lipid layers on polyelectrolyte multilayer supports

et al. 2008

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The mechanism of formation of supported lipid layers from phosphatidylcholine and phosphatidylserine vesicles in solution on polyelectrolyte multilayers was studied by a variety of experimental techniques. The interaction of zwitterionic and acidic lipid vesicles, as well as their mixtures, with polyelectrolyte supports was followed in real time by micro-gravimetry. The fabricated lipid-polyelectrolyte composite structures on top of multilayer coated colloidal particles were characterized by flow cytometry and imaging techniques. Lipid diffusion over the macroscopic scale was quantified by fluorescence recovery after photobleaching, and the diffusion was related to layer connectivity. The phospholipid-polyelectrolyte binding mechanism was investigated by infrared spectroscopy. A strong interaction of polyelectrolyte primary amino groups with phosphate and carboxyl groups of the phospholipids, leading to dehydration, was observed. Long-range electrostatic attraction was proven to be essential for vesicle spreading and rupture. Fusion of lipid patches into a homogeneous bilayer required lateral mobility of the lipids on the polyelectrolyte support. The binding of amino groups to the phosphate group of the zwitterionic lipids was too weak to induce vesicle spreading, but sufficient for strong adsorption. Only the mixture of phosphatidylcholine and phosphatidylserine resulted in the spontaneous formation of bilayers on polyelectrolyte multilayers. The adsorption of phospholipids onto multilayers displaying quarternary ammonium polymers produced a novel 3D lipid polyelectrolyte structure on colloidal particles.

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“…Much stronger effects are observed when polyelectrolyte copolymers or graft polymers, often with hydrophobic side chains, are used for a more efficient anchoring of the polyelectrolyte chain into the lipid bilayer structure, thus enhancing the formation of pores within the lipid bilayer membrane. A large variety of hydrophobic graft copolymers can be used to generate transient pores within the membrane, such as PS-alt-MAA 3 (poly(styrene-alt-methacrylic acid), [27] poly(maleic acid) copolymers 4, [28] octyl-modified poly(acrylic acid), [29,30] octadecyl-modified dextrane, [31] or various acrylamides. [32] ) Usually, only a small fraction of hydrophobic moieties (a few mol %) is needed within the polymer to effect an efficient pore formation, whereas a higher content of the polyelectrolyte within the copolymer leads to a more efficient leakage of the membrane, as recently studied by Wang et al [33] by using copolymers of acrylamide and poly-(acrylic acid) 5.…”

mentioning

confidence: 99%