Structure of lipid bilayers

12.2.2. Four-Wave Mixing (FWM) 4849 12.2.3. Dye Aggregation 4850 12.2.4. Optoelectronic Nanodevices 4850 12.3. Sensor 4851 12.3.1. Chemical Sensor 4851 12.3.2. Biological Sensor 4851 12.4. Catalysis 4852 13. Conclusion and Perspectives 4852 14. Abbreviations 4853 15. Acknowledgements 4854 16. References 4854 * Corresponding author E-mail: tpal@chem.iitkgp.ernet.in. † Raidighi College. § Indian Institute of Technology. 4797 Chem. Rev. 2007, 107, 4797−4862

Interparticle Coupling Effect on the Surface Plasmon Resonance of Gold Nanoparticles: From Theory to Applications

Cationic liposomes complexed with DNA (CL-DNA) are promising synthetically based nonviral carriers of DNA vectors for gene therapy. The solution structure of CL-DNA complexes was probed on length scales from subnanometer to micrometer by synchrotron x-ray diffraction and optical microscopy. The addition of either linear lambda-phage or plasmid DNA to CLs resulted in an unexpected topological transition from liposomes to optically birefringent liquid-crystalline condensed globules. X-ray diffraction of the globules revealed a novel multilamellar structure with alternating lipid bilayer and DNA monolayers. The lambda-DNA chains form a one-dimensional lattice with distinct interhelical packing regimes. Remarkably, in the isoelectric point regime, the lambda-DNA interaxial spacing expands between 24.5 and 57.1 angstroms upon lipid dilution and is indicative of a long-range electrostatic-induced repulsion that is possibly enhanced by chain undulations.

https://science.sciencemag.org/content/sci/275/5301/810.full.pdf

Structure of DNA-Cationic Liposome Complexes: DNA Intercalation in Multilamellar Membranes in Distinct Interhelical Packing Regimes

Supramolecular nanotube architectures based on amphiphilic molecules.

A two-dimensional columnar phase in mixtures of DNA complexed with cationic liposomes has been found in the lipid composition regime known to be significantly more efficient at transfecting mammalian cells in culture compared to the lamellar (LalphaC) structure of cationic liposome-DNA complexes. The structure, derived from synchrotron x-ray diffraction, consists of DNA coated by cationic lipid monolayers and arranged on a two-dimensional hexagonal lattice (HIIC). Two membrane-altering pathways induce the LalphaC --> HIIC transition: one where the spontaneous curvature of the lipid monolayer is driven negative, and another where the membrane bending rigidity is lowered with a new class of helper-lipids. Optical microscopy revealed that the LalphaC complexes bind stably to anionic vesicles (models of cellular membranes), whereas the more transfectant HIIC complexes are unstable and rapidly fuse and release DNA upon adhering to anionic vesicles.

/pdf/an-inverted-hexagonal-phase-of-cationic-liposome-dna-4njfymrwch.pdf

An inverted hexagonal phase of cationic liposome-DNA complexes related to DNA release and delivery

Mise en evidence de la structure par des etudes de diffusion de rayons X haute resolution d'echantillons minces smectiques C prepares entre deux lames solides par refroidissement a partir de la phase smectique A

"Chevron" local layer structure in surface-stabilized ferroelectric smectic-C cells.

We report a high-resolution x-ray study of a model multilayer fluid membrane system in the lyotropic L/sub ..cap alpha../ phase of a quaternary microemulsion system. The structure factor exhibits power-law behavior characteristic of a Landau-Peierls system. As a function of intermembrane distance 3.8 nmless than or equal todless than or equal to16.3 nm, the exponent eta(d) which describes the algebraic decay of layer correlations is predicted by the model of Helfrich where entropic steric repulsions dominate intermembrane interactions.

Steric interactions in a model multimembrane system: A synchrotron x-ray study.

We report on synchrotron x-ray scattering studies of multimembrane systems in the fluid L/sub ..cap alpha../ phase. By embedding cosurfactant molecules in a model biological membrane (di-myristoyl-phosphoridyl-choline) system, we dramatically reduce the bending rigidity of the fluid bilayer. This effect leads to a crossover from a microscopically driven to a fluctuation-induced universal regime for intermembrane interactions. Studies of a homologous cosurfactant series, with varying hydrocarbon chain length between 5 and 12, allow us to attribute this reduction in k/sub c/ to the thinning of the membrane.

Universality in interacting membranes: The effect of cosurfactants on the interfacial rigidity.

We report a high-resolution, small-angle x-ray study of aggregated gold colloids over the range 0.0003 to 0.08 ${\mathrm{\AA{}}}^{\ensuremath{-}1}$. We are able to fit our data with a simple model that correctly accounts for nonfractal short-range order with a crossover to long-range fractal correlations. This provides new information on the structure of real aggregates, and new insight into the aggregation processes which lead to their formation.

Structure of aggregated gold colloids.

We report x-ray measurements on well aligned, freely suspended films of stacked bilayer membranes of the phospholipid dimyristoyl-phosphatidylcholine in a continuously variable humidity- and temperature-controlled environment. Remarkably, the most commonly observed L/sub ..beta..//sub '/ phase is in fact three distinct 2D phases where the phase transitions are driven by hydration forces and the phases are distinguished by the relation between the molecular tilt direction and the 2D bond direction.

G. S. Smith

Papers

"Chevron" local layer structure in surface-stabilized ferroelectric smectic-C cells.

Steric interactions in a model multimembrane system: A synchrotron x-ray study.

Universality in interacting membranes: The effect of cosurfactants on the interfacial rigidity.

Structure of aggregated gold colloids.

Structure of the L β phases in a hydrated phosphatidylcholine multimembrane